CHRONIC LYMPHOCYTIC LEUKEMIA AND RELATED DISEASES

Chronic lymphocytic leukemia (CLL) is a neoplastic disease characterized by the accumulation of small mature-appearing CD5+ B lymphocytes in the blood, marrow, and lymphoid tissues. The causes of this disease are unknown, although it appears likely that genetic factors contribute to its development. The leukemic cells from nearly 50 percent of CLL patients can be found to have clonal chromosomal abnormalities, of which del 13q14-23.1 is the most common chromosomal abnormality in CLL, followed in order by trisomy 12, del 11q22.3-q23.1, del 6q21-q23, and 14q abnormalities. Mutations of the P53 tumor suppressor gene at 17q13 are uncommon except in advanced disease. Assessing for clinical stage and various prognostic markers can be useful in deciding when to initiate therapy. Treatment with chlorambucil, with or without prednisone, has been the mainstay of initial treatment, although recent studies confirm the high activity of deoxyadenosine analogs such as fludarabine in this disease. Combination drug therapy has not been shown to be more effective as front-line therapy. However, new drug combinations, autologous and allogeneic stem cell transplantation, monoclonal antibodies, and gene therapy are being evaluated, as there are no established cures or demonstrated survival benefit from current treatments. This chapter also discusses prolymphocytic leukemia, which can be of B- or T-cell origin. The latter includes cases that formerly were designated T-cell CLL. Although B-cell prolymphocytic leukemia can evolve from preexisting cases of CLL, it has many distinctive features including a more adverse clinical outcome. Treatments for B-cell prolymphocytic leukemia are similar to those used in CLL, but the response rates are lower and of shorter duration. Similarly, T-cell prolymphocytic leukemia is more aggressive than CLL. Rearrangements and mutations in the ataxia-telangiectasia mutated gene and in T-cell leukemia 1 (TCL-1) and related genes apparently contribute to the pathogenesis of T-cell prolymphocytic leukemia. About a third of patients will have cutaneous involvement causing erythroderma. Treatment with deoxyadenosine analogs appears effective in a subset of patients with this disease. Investigation into the use of new agents, stem cell transplantation, and/or monoclonal antibodies, such as CAMPATH-1H, is ongoing, as there are no established cures.

Acronyms and abbreviations that appear in this chapter include: ACE, cytosine arabinoside, cisplatin, and etoposide; ADCC, antibody-dependent cellular cytotoxicity; A-T, ataxia-telangiectasia; ATM gene, ataxia-telangiectasia mutated gene; BCL-1, B-cell leukemia 1; CAP, cyclophosphamide, doxorubicin, and prednisone without vincristine; CCP, cladribine in combination with cyclophosphamide and prednisone; CHOP, cyclophosphamide, doxorubicin, vincristine, and prednisone; CLL, chronic lymphocytic leukemia; CTL, cytotoxic T lymphocytes; CVP, cyclophosphamide, vincristine, and prednisone; DBM, disrupted in B-cell malignancies; DiSC, differential staining cytotoxicity; EBV, Epstein-Barr virus; FAB Cooperative Group, French-American-British Cooperative Group; FC, fludarabine/cyclophosphamide; FISH, fluorescence-in-situ hybridization; GM-CSF, granulocyte-macrophage colony-stimulating factor; G6PD, glucose-6-phosphate dehydrogenase; GVHD, graft-versus-host disease; HCV, type C hepatitis virus; HTLV-I, human T lymphotropic virus type I; HTLV-1+, human T lymphotropic virus type I-positive adult T-cell leukemia/lymphoma; ICAM, intercellular adhesion molecule; IL-6, interleukin 6; LDH, lactate dehydrogenase; LT-a, lymphotoxin alpha; MDR-1, multidrug resistance 1 gene; MEN-1, multiple endocrine neoplasia syndrome type 1; NF-2, neurofibromatosis type 2 tumor suppressor gene; Pgp, P-glycoprotein; PLL, prolymphocytic leukemia; RDX, radixin; Rh-IL-6, recombinant human interleukin 6; SCL, Sézary-cell leukemia; SCT, stem cell transplantation; SS, Sézary syndrome; sVCAM-1, soluble vascular cell adhesion molecule 1; TCL-1, T-cell leukemia 1; TdT, terminal deoxynucleotidyl transferase; TGF-b, transforming growth factor beta; TK, thymidine kinase; TNF-a, tumor necrosis factor alpha; TRAP, tartrate-resistant isozyme 5 of acid phosphatase; TSEB, total skin electron beam; VAD, vincristine, doxorubicin, and dexamethasone; VCAM-1, vascular cellular adhesion molecule 1; YAC, yeast artificial chromosome.

CHRONIC LYMPHOCYTIC LEUKEMIA
DEFINITION AND HISTORY
Chronic lymphocytic leukemia is a neoplastic disease characterized by the accumulation of small mature-appearing lymphocytes in the blood, marrow, and lymphoid tissues. CLL has an average incidence of 2.7 persons per 100,000 in the United States. The risk of developing CLL increases progressively with age and is 2.8 times higher for older men than for older women.1 Because of its relative indolence, this disease accounts for approximately 0.8 percent of all cancers and nearly 30 percent of all leukemias at any point in time. It is the most common adult leukemia in Western societies. Generally, the neoplastic lymphocytes are of the B-cell lineage. In less than 2 percent of cases, however, the neoplastic cells are of T-cell origin and are considered under the heading T-cell prolymphocytic leukemia.
The first descriptions of patients with CLL were published in the early nineteenth century.2,3 and 4 In the 1840s, Virchow described two forms of chronic leukemia, these probably corresponding to CLL and chronic myelogenous leukemia.4,5 and 6 Patients with the former were noted to have mild-to-moderate splenic enlargement, lymphadenopathy, and large numbers of small agranular cells in the blood that resembled those found in enlarged lymph nodes.5 Virchow considered this type of leukemia to be principally related to disease of the lymph nodes rather than of the spleen. In 1893, Kundrat introduced the term lymphosarcoma to describe an indolent disease that affected lymph nodes.7 Histochemical staining techniques introduced by Ehrlich at the turn of the century8 made it possible for pathologists to distinguish between myeloid and lymphocytic leukemias. These methods enabled Türk in 1903 to establish a relationship of the leukemic cells in CLL to those in lymphosarcoma.9 He proposed the term lymphomatoses to describe several lymphoproliferative disorders including CLL. Owing to its indolent nature, CLL was considered a “benign” lymphomatosis.
In 1924, Minot and Isaacs described the natural history of 98 patients with CLL,10 challenging the notion that CLL was a “benign” process. These investigators noted that although gamma radiation could reduce lymph node enlargement or splenomegaly, it apparently did not prolong survival. Radioactive phosphorus later was found effective in reducing lymph node swelling.11 However, this also was noted to be of limited therapeutic value because of its marrow toxicity and its inability to reverse disease-related cytopenias or to improve survival.11 In 1954, Tivey published the survival data of 685 patients with CLL, observing that the median survival time was approximately 3 years from the onset of symptoms related to CLL.12 Soon thereafter, alkylating agents,13 and later glucocorticoids,14 were found to be effective therapy for CLL. These agents became the mainstays of treatment.
In 1967, Dameshek hypothesized that CLL was an accumulative disease of immunologically incompetent lymphocytes.15 In the early 1970s, the leukemic cells from most cases of CLL were found to express surface immunoglobulin, indicating that the neoplastic cells were of B-cell origin.16 Subsequent studies demonstrated that the CLL cells of female patients who were heterozygous for glucose-6-phosphate dehydrogenase (G6PD) expressed only one G6PD allele,17 indicating that the leukemia cells arose from a single B-cell clone. Consistent with this notion, the CLL cells from any one patient were found to express only one type of immunoglobulin light chain18 and idiotype,19,20 and 21 indicating their uniformity in the expression of immunoglobulin.
A clinical staging system for patients with CLL was introduced in 1975 by Rai and colleagues,22 delineating the adverse implication of anemia or thrombocytopenia on patient survival. In the late 1980s, purine analogs, such as fludarabine or 2′-chlorodeoxyadenosine (cladribine), were found to be effective in the treatment of CLL. Other treatment modalities are being examined, including passive or active immunotherapy or ablative chemotherapy with marrow transplantation, as the disease still is not considered curable.
ETIOLOGY AND PATHOGENESIS
ENVIRONMENTAL FACTORS
Environmental factors do not appear to play a role in the pathogenesis of B-cell CLL. Although one study noted an increase in CLL in a rural farming community,23 the incidence of CLL was not associated with exposure to pesticides, sunlight, ionizing radiation, or known carcinogens.24,25,26,27,28 and 29 A few epidemiologic studies have noted an increase in CLL among persons chronically exposed to electromagnetic fields.30,31 and 32 However, it is not determined whether this association reflects a causal relationship.
Antibodies specific for type C hepatitis virus (HCV) and/or viral DNA have been identified in some patients, suggesting a pathogenic role.33 However, more recent studies have failed to verify an association between the development of CLL and infection with hepatitis C virus.34,35 CLL cells are resistant to infection with Epstein-Barr virus (EBV), except in unusual cases,36 making it unlikely that EBV plays a pathogenic role.
The incidence of CLL in men is twice that of women. One retrospective study of women noted a nonsignificant trend toward reduced risk of CLL with increasing parity, prompting speculation that pregnancy lowers the risk for CLL.37 However, hormones have not been demonstrated to play any role in the development of CLL.
HEREDITARY FACTORS
Genetic factors apparently contribute to the development of CLL. Although B-cell CLL is the most common adult leukemia in Western societies, it is relatively rare in Asia. In the United States, the annual incidence of CLL is 3.9 or 2.0 per 100,000 males or females, respectively. However, in Korea, the estimated incidence of this disease is only 1.5 percent of this rate.38 Similarly, B-cell CLL is relatively uncommon in China and rare in Japan.39,40 and 41 A very low incidence of B-cell CLL is noted even among Japanese immigrants to the United States.39,42 Likewise, the incidence of B-cell CLL in Israel is significantly higher among European immigrants than among those from Africa or Asia.43
Although most cases of CLL are sporadic, multiple cases of CLL may be found within a single family. There are numerous reports of families with multiple members having B-cell CLL.44,45,46,47,48 and 49 First-degree relatives of patients with CLL are more than three times at risk for having this disorder or other lymphoid neoplasms than is the general population.47 Afflicted individuals within such families often present at a younger age than most patients with CLL, suggesting that genetic factors in familial CLL may contribute to early leukemogenesis.
The genetic factors that contribute to the increased incidence of CLL in certain families are unknown. There is no apparent association between HLA haplotype and disease susceptibility.50 One study noted that the leukemic cells of affected family members sometimes might express the same immunoglobulin heavy-chain variable region gene.51 However, each patient’s leukemia cells have distinct immunoglobulin gene rearrangements,48,51 even those of monozygous twins,52 indicating that they originate from distinct somatic events.
GENETICS
Detection of chromosomal abnormalities initially was hampered by the inability to induce leukemic cell proliferation. These cells generally do not grow spontaneously in cell culture and are much more refractory to activation by mitogens or to transformation by Epstein-Barr virus than normal B cells.15,53 As such, the normal karyotypes noted in some samples could reflect an outgrowth of normal bystander lymphocytes.
Using Q-banding and/or G-banding techniques (see Chap. 10), and improved methods for inducing leukemia-cell proliferation in vitro,54,55 the leukemic cells from nearly 50 percent of CLL patients are noted to have clonal chromosomal abnormalities.56,57,58 and 59 Interphase cytogenetics using fluorescence-in-situ hybridization (also referred to as FISH) has increased the sensitivity for detecting translocations, deletions, or chromosome trisomy. Using these techniques, it appears that del 13q14-23.1 is the most common chromosomal abnormality in CLL, followed in order by trisomy 12, del 11q22.3-q23.1, del 6q21-q23, 14q abnormalities, and deletions/mutations of the P53 tumor suppressor gene at 17q13.60 Deletions or duplications account for most of the observed genetic defects, as chromosomal translocations are relatively rare in CLL.
Chromosome 13 Anomalies Deletions on the long arm of chromosome 13 are the most common genetic abnormality in CLL. These deletions generally occur in the absence of chromosome translocation. Nevertheless, those CLL cells with translocations often are noted to have ones involving the long arm of chromosome 13 with any one of several different chromosomes.61 Because these translocations generally result in deletions at 13q14, deletions at 13q14 may be the contributing genetic lesion, rather than translocation per se.
Deletions in the long arm of chromosome 13 can be detected in approximately half of the cases of CLL. One group noted deletions at 13q12.3, in and around the breast cancer susceptibility gene, BRCA2, in the leukemia cells of 80 percent of 35 CLL patients.62 Subsequent studies by other investigators, however, failed to confirm this.63 Instead, these and several other groups have identified deletions at 13q14.3, particularly in a region that is telomeric to the retinoblastoma gene RB-1 and centromeric to and including the D13S25 marker.64,65,66,67 and 68 A tumor suppressor gene is hypothesized to reside in this region, referred to as DBM (for disrupted in B-cell malignancies). Candidate tumor suppressor genes that map to this region include LEU1 and LEU2.69 However, CLL cells do not appear to have mutations in both alleles of these genes, making it less likely that they are the actual tumor suppressor genes involved in CLL. Another candidate tumor suppressor gene is LEU5. This gene encodes a zinc-finger domain of the RING type and shares homology with genes involved in tumorigenesis, including the RET finger protein and BRCA1.70
Chromosome 12 Anomalies Trisomy 12 is found in the leukemia cells of 10 to 30 percent of all patients with CLL.71,72 However, studies using molecular techniques, such as fluorescence-in-situ hybridization, have noted a higher proportion of cases with trisomy 12, as well as other chromosomal abnormalities.58,73,74 and 75 Studies using restriction fragment length polymorphism analysis revealed that the leukemia cells with trisomy 12 have one duplicated chromosome 12, while retaining the other homologue.76,77 As such, it appears that this genetic lesion is not recessive, as would be the case for the loss of a tumor suppressor gene, but rather provides for a gene dosage effect. More recent studies on partial trisomy 12 are consistent with this notion, suggesting that trisomy 12 reflects a gene dosage effect of some genes located between 12q13 and 12q22.71
Trisomy 12 may be a secondary event that occurs within an established leukemic clone, or preleukemic B cell.78 Leukemia cells with trisomy 12 often have complex karyotypic abnormalities79 and atypical and/or prolymphocytic morphology.65,71,80,81 and 82 One study using fluorescence-in-situ hybridization found that nearly half of the cases with 13q14 deletions also had trisomy 12.83 Trisomy 12 may not be detectable at diagnosis but is more commonly seen in the leukemia cells of patients with advanced disease or who develop Richter transformation.79,84,85 Furthermore, this abnormality often may be detected in only a subset of the leukemia cells from any one patient.86,87 Finally, studies suggest that the leukemia-cell subset with trisomy 12 may expand during disease progression.64 Collectively, these studies suggest that trisomy 12 is acquired during the evolution of the disease, rather than being a defining genetic event in the etiopathogenesis of CLL.
Chromosome 11 Anomalies Approximately 10 to 20 percent of patients may have leukemia cells with deletions in the long arm of chromosome 11, termed 11q–.88,89 and 90 These patients tend to be younger in age (less than 55 years) and to have more aggressive disease than those without such genetic changes.89 Furthermore, the leukemia cells of such patients may express lower levels of surface CD11a/CD18, CD11c/CD18, CD31, CD48, and CD58 than CLL cells from patients without 11q–, arguing that such cells may have a distinctive biology.91
CLL B cells can have translocations or deletions involving 11q13, a region that contains the tumor suppressor gene associated with multiple endocrine neoplasia syndrome type I (MEN-1).92 However, deletions on chromosome 11 more commonly cluster between 11q14-24, particularly at 11q22.3-q23.1, in a region defined by yeast artificial chromosome (YAC) clones 801e11, 975h6, and 755b11.88,89 Potential tumor suppressor genes within this region include ATM and RDX. RDX, or radixin, has homology with the neurofibromatosis type 2 tumor suppressor gene (NF-2). ATM, on the other hand, is the gene mutated in ataxia-telangiectasia. Upon DNA damage, the normal gene plays an important role in the activation of the tumor suppressor gene-product P53, leading to cell-cycle arrest and DNA repair.93 The ATM gene has been noted to be lost through deletion or mutation in leukemia cells of patients with relatively aggressive disease.88,89,94,95 and 96 Some CLL patients carry one defective copy of this gene in the germ-line DNA, suggesting that mutations in ATM may be involved in the pathogenesis of aggressive B-CLL.95,97
Chromosome 6 Anomalies Another recurring chromosome abnormality involves the short arm of chromosome 6, but the genes altered have not been identified.65 The most frequent abnormalities on chromosome 6 involve breaks between 6q23 and 6q24, frequently resulting in deletions at 6q25-27, 6q21, and particularly 6q23.98,99,100 and 101 Patients with abnormalities between 6q21 and 6q24 generally have higher proportions of blood prolymphocytes and more aggressive disease.
One study described an association between CLL and particular alleles of the gene encoding tumor necrosis factor alpha (TNF-a),102 designated TNF-1 and located on 6q, 220 kb centromeric of the major histocompatibility complex. In addition, patients with aggressive disease had a particular allele of a contiguous gene encoding lymphotoxin alpha (LT-a), designated TNFB*2, more often than control subjects. These alleles are associated with functional differences in the levels of inducible TNF-a or LT-a. Prospective studies are required to determine whether such alleles are genetic risk factors for CLL.
Chromosome 14 Anomalies Located on chromosome 14, at band 14q32, are the genes encoding the immunoglobulin heavy chain (see Chap. 83). This band frequently is the site of translocations in B-cell malignancies, with breakpoints often occurring within or near the immunoglobulin heavy-chain J segment minigenes or the immunoglobulin heavy-chain isotype switch regions.103 Band q11.2 of chromosome 14 also contains genes encoding the a chain and the d chain of the human T-cell receptor (see Chap. 84). Leukemic cells with inversions of chromosome 14, inv(14) (q11q32), most often are derived from the T-cell lineage and express T-cell differentiation antigens.104,105 and 106 These lesions are common in T-cell prolymphocytic leukemia. Translocations at either of these loci are postulated to reflect an aberrant immunoglobulin or T-cell receptor gene rearrangement that in turn activates a proto-oncogene located on the other chromosome involved in the translocation.
t(11;14)(q13;q32) A small minority of patients with B-cell CLL may have leukemia cells with translocations involving chromosome 14, at band 14q32, and chromosome 11, at band 11q13, or t(11;14)(q13;q32).59,107,108 and 109 The translocation juxtaposes the heavy-chain immunoglobulin genes with a proto-oncogene, designated BCL-1, for B-cell leukemia 1,107,110 that subsequently was identified as PRAD1, a gene encoding cyclin D1.111,112 Overexpression of PRAD1 can contribute to cell transformation113 and may play a role in the development of some cases of B-cell CLL.113 However, among lymphoid malignancies, the highest incidence of t(11;14) and/or PRAD1 overexpression is noted in mantle zone cell lymphoma.114,115,116,117 and 118 Because the neoplastic B cells of this intermediate-grade lymphoma can share many phenotypic features with the leukemic B cells in CLL (see Chap. 96 and Chap. 103), cases of CLL that previously were thought to have t(11;14)(q13;q32) instead may have represented the leukemic phase of mantle cell lymphoma.116,117,119,120 and 121
t(14;18) Rarely, the leukemic cells in B-cell CLL can have t(14;18) translocations that more commonly are found in low-grade nodular B-cell lymphomas (see Chap. 103),122,123 This translocation juxtaposes the immunoglobulin heavy chain genes with the BCL-2 oncogene.
t(14;19)(q32;q13.1) Although an initial report of t(14;19) translocations in CLL found this translocation in 3 of 30 cases,124 cytogenetic analyses of 4487 patients with indolent lymphoproliferative diseases, including those with CLL, revealed only six cases to have t(14;19).125 Only 23 CLL cases have been reported to have t(14;19) to date. Such translocations generally involve the isotype switch regions of IgA on chromosome 14 and result in increased, transcription of BCL3, a gene near the breakpoint on chromosome 19 that encodes a protein of the IkB family of transcription factors.125,126 There is a striking association of t(14;19) with trisomy 12. The presence of this and other CLL-associated features argues that patients with t(14;19) do not have a lymphoproliferative disease distinct from that of CLL. Rather, t(14;19) may be an acquired cytogenetic abnormality that occurs during the evolution of preexisting CLL.
ABNORMALITIES IN SPECIFIC GENES
P53 The P53 gene, located on the short arm of chromosome 17 at 17p13.1, encodes a 53-kDa nuclear phosphoprotein.127 Upon damage to the cell’s DNA, P53 plays an important role in inducing p21/WAF1, leading to inhibition of cyclin-dependent kinase activity; failure to phosphorylate key substrates, such as the retinoblastoma protein; and consequent cell-cycle arrest. Mutations or defects in this gene probably play a pathogenic role in nearly half of all human cancers128,129 (see Chap. 10).
However, deletions in the short arm of chromosome 17, in and around P53, have been noted in leukemia cells from only about 10 to 15 percent of patients.82 A similar proportion of patients are noted to have leukemic cells with mutations in the P53 gene.130,131,132 and 133 These mutations commonly occur in the highly conserved exons 4 through 8 of the P53 gene and often are associated with loss of heterozygosity for chromosome 17p.132
Patients who have CLL cells with P53 mutations generally have more advanced disease, a higher leukemia-cell proliferative rate, a shorter survival, and greater resistance to first-line therapy.133,134,135 and 136 Moreover, the neoplastic cells from nearly half of the patients with Richter transformation or B-cell prolymphocytic leukemia have been noted to have P53 mutations.130 As such, it appears that P53 gene mutations are acquired in some B-cell CLL, resulting in leukemic cells that have a selective growth advantage and a more aggressive clinical behavior.
Multidrug-Resistance (MDR) Gene The leukemic cells from approximately 40 percent of CLL patients express elevated levels of the multidrug resistance 1 gene, designated MDR-1, especially in response to chemotherapy.137,138,139,140,141 and 142 MDR-1, located on the long arm of chromosome 7 at 7q21.1, encodes a 170-kDa transmembrane P-glycoprotein (Pgp) that can function as an energy-dependent, efflux pump for a wide variety of cytotoxic drugs, thus lowering their intracellular concentration to sublethal levels.143 Elevated expression of this gene appears to be peculiar to the CLL B cell, as it is not noted in normal B cells.139 However, because MDR-1 can be induced by treatment or by changes in a preexistent leukemia clone, aberrant MDR gene expression more likely plays a role in disease progression of some B-cell CLL rather than in primary pathogenesis.
BCL-2 Approximately 5 percent of CLL patients may have leukemic cells that have aberrant immunoglobulin gene rearrangements with the BCL-2 proto-oncogene located on the long arm of chromosome 18, at 18q21.122,123,144 In contrast to BCL-2 gene rearrangements in nodular B-cell lymphomas, the rearrangements in B-cell CLL generally occur at breakpoints in the 5′-end of the BCL-2 gene and involve the k or l immunoglobulin light-chain genes on chromosomes 2 or 22, respectively.144 Independent of BCL-2 gene rearrangement, however, the leukemic cells from nearly all patients with B-cell CLL express high levels of the bcl-2 protein that are comparable to that noted for lymphoma cells carrying the t(14;18)(q32;q21) translocation.145,146 This is associated with hypomethylation of the BCL-2 locus.147 Using pulse-field gel electrophoresis to examine for BCL-2 gene rearrangements in DNA fragments of 50,000 to 10,000 kilobases, one study found that each of nine CLL cases had somatic rearrangements that would not have been detected by conventional techniques.148 This suggests that there may be previously undetected genetic abnormalities in CLL involving chromosome 18 that may be responsible for the high-level expression of the BCL-2.
IMMUNOGLOBULIN GENES
Immunoglobulin Characteristics The leukemic cells from over 90 percent of patients express low levels of monoclonal surface immunoglobulin with either k or l light chains. Sixty percent of cases express k light chains, while the other 40 percent express l light chains.149,150 and 151 Of the heavy-chain isotypes, over half of all cases have surface IgM and IgD (55 percent), a quarter have IgM exclusive of IgD, and approximately 7 percent have immunoglobulin isotypes other than IgM or IgD (usually IgG or IgA). Less than 5 percent of cases express IgD without detectable IgM. Both IgM and IgM/IgD expressing CLL frequently express cross-reactive idiotypes (see Chap. 83) that commonly are found on IgM autoantibodies.152
The immunoglobulins expressed in B-cell CLL often have reactivity for self-antigens, most notably for the constant region of human IgG (reviewed in Caligaris-Cappio153). An important feature of these autoantibodies is their “polyreactivity,” or binding activity for two or more seemingly disparate self-antigens. Such polyreactivity is a characteristic of some antibodies produced during early B-cell development, even in animals raised in apparent germ-free environments.154,155 Because of this, several investigators have used the term natural autoantibodies to describe these autoantibodies.
Immunoglobulin Variable Region Genes CLL B cells can be segregated into at least two groups that differ in the extent to which their expressed immunoglobulin variable region genes (V genes) have undergone somatic mutation.156 About half of all cases have leukemia cells that express nonmutated V genes, whereas the rest express V genes with levels of base substitutions that distinguish them from their germ-line counterparts. As such, the later resemble more the cases of CLL that express IgA or IgG.157,158,159 and 160 The extent to which V genes are mutated does not vary within any one leukemia cell population,161 even when examined over a period of years.162
The leukemia cells from approximately 5 percent of CLL patients, however, may lack immunoglobulin heavy-chain allelic exclusion163 (see Chap. 83). Leukemia cells lacking allelic exclusion express at least two different immunoglobulin heavy chains encoded by each allele. Some leukemia cells have been found to express both mutated and nonmutated immunoglobulin V genes simultaneously.163 This may complicate the use of somatic mutation as a means to segregate distinct leukemia subtypes.
Nevertheless, CLL B cells that express nonmutated immunoglobulin V genes may constitute a distinct subset of CLL. Leukemia cells that express nonmutated immunoglobulin V genes may have trisomy 12 and atypical morphology more often than those that expressed mutated immunoglobulin V genes, which in turn more frequently tend to have abnormalities involving 13q14.164 Furthermore, patients with leukemia cells that express mutated immunoglobulin V genes may have a more indolent clinical course than patients with leukemia cells that express nonmutated immunoglobulin V genes.165,166
Certain immunoglobulin V genes expressed by CLL B cells may play a role in leukemogenesis. Some V genes, such as the 51p1 allele of VH1-69, are expressed at high frequency and without mutation in CLL.167 Moreover, CLL B cells that express the 51p1 have restricted use of certain amino acid sequences within the third complementarity determining region156,168 (see Chap. 83). This restriction is not a feature of “polyreactive antibodies” per se or of antibodies expressed by B cells during fetal development.169,170 Rather, it appears that the antibodies used in CLL may be selected because of some undefined binding specificity and/or play a role in leukemogenesis.
CYTOGENESIS
Immunophenotype The leukemic cells of most patients express pan-B-cell surface antigens, such as CD19 and CD20 (see Chap. 13), indicating that they are derived from the B-lymphocyte lineage. The level at which the CD20 antigen is expressed, however, is substantially lower than that found on normal circulating B cells.171,172 and 173
Some of the patterns of lymphoid infiltration in CLL reflect expression of certain integrins.174,175 CLL B cells generally express the b1 (CD29) and b2 (CD18) integrins with varying amounts of a3 (CD49c), a4 (CD49d), or a5 (CD49e). The a chains that normally are associated with b1, such as a2 (CD49b), a6 (CD49f), or aV (CD51), generally are not expressed in CLL. Also, expression of the b2 integrins, such as leukocyte function antigen-1 (LFA-1), is variable. In one study,175 low-level expression of b2 integrins was associated with a diffuse marrow infiltrate and aggressive disease.
The leukemia cells from most patients also express ligands for LFA-1, namely intercellular adhesion molecule (ICAM)-1 (CD54), ICAM-2 (CD102), and ICAM-3 (CD50).176 CLL cells can bind weakly to nonstimulated endothelium via such ICAMs. Stimulation of endothelium to express the vascular cellular adhesion molecule 1 (VCAM-1) allows for enhanced binding of CLL cells that express the VCAM-1 ligand, a4b1.174 Expression of a4b1 also may allow the CLL cells to localize at major sites of VCAM-1 expression, e.g., marrow, liver, and spleen.
CD5 B Cells (B1 B Cells) The leukemic cells of more than 95 percent of patients express CD5 (Leu 1, OKT1). Most cases of CLL with monoclonal leukemia B cells that do not express CD5 actually may be found to represent lymphoproliferative diseases other than CLL upon more rigorous phenotypic and pathologic analyses.177
The physiologic counterpart to such cells is the CD5 B cell.178 These cells constitute a small subpopulation of human B lymphocytes in the lymphoid organs and peripheral blood of normal adults and most B cells in fetal spleen. Human B cells in lymphoid tissue that express CD5 reside primarily in the mantle zones surrounding the germinal centers of secondary B-cell follicles.179 These cells are enriched for B cells that spontaneously may produce polyreactive IgM autoantibodies180,181 and frequently express autoantibody-associated cross-reactive idiotypes.179,182 Although they share many characteristics, these cells may not be phenotypically identical with CLL B cell.183
Because detectable levels of the CD5 antigen (1) are not noted on all B cells that otherwise satisfy other criteria for “CD5 B cells,”184 (2) may be induced on non-“CD5 B cells,”185,186 and (3) can be reduced on “CD5 B cells” by treatment with various cytokines,187 the term CD5 B cell was not considered adequate. For these reasons, long-lived, recirculating, and/or self-replenishing B cells that are enriched for cells expressing “natural” IgM autoantibodies are referred to by many investigators as B-1 B cells.188 Short-lived B cells that are generated continuously in the adult marrow are referred to as conventional, or B-2 B, cells.
LEUKEMIA CELL ACCUMULATION
Growth Kinetics There is a small pool of proliferating cells. In the spleen, proliferation of CLL cells occurs preferentially in the white pulp zones, even in cases in which both the white and red pulp are extensively infiltrated.189 However, CLL cells in the blood incorporate extremely low amounts of 3H-thymidine in vitro190 and are mainly in the G0 stage of the cell cycle, as assessed by flow cytometry.191 Because most CLL cells are not proliferating, the life span of CLL lymphocytes appears long. Consistent with this, human CLL B cells can survive for many weeks after transfer into mice with severe combined immune deficiency.192
Resistance to Apoptosis CLL cells accumulate, as they are resistant to programmed cell death, or apoptosis (see Chap. 11). CLL B cells express high-levels of the anti-apoptotic protein bcl-2.147,193,194,195,196,197,198,199 and 200 In addition, the neoplastic B cells of patients with CLL also characteristically express high levels of other anti-apoptotic proteins, such as bcl-xL, mcl-1, and bag-1,201 and low levels of the pro-apoptotic protein bax or bcl-xs.195 Bcl-2 and bax proteins form homodimers and heterodimers that influence the susceptibility to apoptosis.202,203 Moreover, it appears that the relative ratio of bcl-2 and/or bcl-xL to bax in leukemia cells is related to their resistance to drugs in vitro194,196,199,204 and possibly also in vivo.
Drugs that are active in the treatment of CLL can alter the relative ratio of bcl-2 to bax. Increasing the relative concentration of bcl-2 decreases the relative sensitivity to apoptosis, whereas increasing the relative concentration of bax increases contributes to cell death (reviewed in Yang and Korsmeyer205). In vitro, fludarabine (9-b D-arabinofuranosyl-2-fluoradenine, F-ara-A) can down-regulate expression of BCL-2 mRNA and bcl-2 protein by some leukemia cells in vitro. Furthermore, the sensitivity of leukemia cell samples to fludarabine-induced down-regulation of BCL-2 correlated loosely with the therapeutic response to this drug in vivo.206 It remains to be established whether the modulation in the relative levels of bcl-2 to bax by such drugs in vitro can predict the clinical response to such drugs in vivo.
In any case, the sensitivity of CLL cells to undergoing spontaneous- or drug-induced apoptosis may be influenced by the leukemia-cell microenvironment. Glucocorticoids, for example, also may induce a decrease in the relative concentration of bcl-2 to bax in CLL B cells, thereby enhancing leukemia-cell susceptibility to apoptosis.207 However, this effect can be mitigated by contact with cells bearing receptors for certain proteins expressed on the leukemia cell surface, such as CD6.208,209 In addition, CLL B cells can survive for long periods ex vivo when cultured with marrow stromal cells.210,211 The ability of stromal cells to inhibit spontaneous apoptosis in vitro is not mediated by soluble factors, but apparently is dependent upon direct cell-cell contact involving the b1 and b2 integrins.
IMMUNOLOGIC DEFECTS
Most patients with CLL have an acquired immune deficiency.212 CLL patients have an increased risk for herpes zoster infection.213 Also, patients with CLL have a higher risk for skin cancers, including basal cell carcinoma, than age-matched controls.214
Patients with CLL have a greater susceptibility to infection due to numerous factors, including hypogammaglobulinemia, low complement levels,215 functional defects in bystander T cells,216 altered leukemia-cell expression of major histocompatibility complex class II antigens,217 and impaired granulocytic function.218
The leukemia cells themselves can contribute to the immunodeficiency noted in patients with this disease. Leukemia B cells elaborate immune suppressive cytokines, such as transforming growth factor beta (TGF-b),219,220 and release soluble surface molecules, such as CD27,183,221,222 that can interfere with cognate intercellular interactions that are required for immune activation. High levels of TGF-b also may account for the reversal in the ratio of CD4 to CD8 T cells that often is noted in the patients with CLL.223 CLL B cells have little stimulatory activity in autologous or even allogeneic mixed lymphocyte culture.224,225 Aside from TGF-b, this in part is related to the surface phenotype of the leukemic B cells. Important accessory molecules required for cognate B-cell«T-cell interactions, such as CD80 (see Chap. 15 and Chap. 84), are absent or present at low levels on the leukemic cell surface. This makes leukemic cells poor antigen-presenting cells but possible effective inducers of T-cell anergy (see Chap. 84).
CLL B cells also are effective in down-modulating expression of the CD40-ligand (CD154), a surface glycoprotein that ordinarily is expressed on CD4+ T cells following immune activation.226,227 Because CD154 plays a critical role in the development of an immune response (reviewed in Grewal and Flavell228), such down-modulation may be responsible for the immune deficiency that is acquired in CLL. Given the role of CD154 in T-cell induction of immunoglobulin class switching, this acquired functional defect in CD154 may account for the acquired deficiency of CLL patients to produce IgG of each of the various subclasses.229 Indeed, the acquired immune deficiency of patients with CLL has features in common with that of persons with inherited functional defects in the gene encoding CD154 (see Chap. 15 and Chap. 88).
These shared features include the frequent development of intermittent and intercurrent systemic autoimmunity despite profound immune deficiency. Patients with congenital lack of CD154 commonly develop autoimmune hemolytic anemia (see Chap. 55) and immune thrombocytopenic purpura (see Chap. 117).230 These also are the most common autoimmune diseases that develop in patients with CLL.15,231,232 Much less frequently, patients with CLL may develop pure red blood cell aplasia233 or neutropenia231 secondary to the development of autoantibodies against marrow hematopoietic progenitor cells. Although patients with rheumatoid arthritis have been reported to have an increased prevalence of CLL compared to that of the general population,234 CLL patients in general do not appear to have an increased incidence of pathologic autoimmunity other than that directed against hematopoietic cells.231,232 The pathogenic autoantibodies generally do not appear to be produced by the malignant B-cell clone.152
CLINICAL FEATURES
PATIENT POPULATION
At diagnosis, most patients are over 60 years of age, and 90 percent are over age 50. The disease is extremely rare in persons under 25 years of age. There is a 2:1 male to female incidence and prevalence of CLL.
GENERAL SYMPTOMS
Over 25 percent of patients are asymptomatic at diagnosis. Such patients generally are detected because of the discovery of nontender lymphadenopathy or an unexplained absolute lymphocytosis. Otherwise, patients may have only mild symptoms of reduced exercise tolerance, fatigue, or malaise. Patients may experience such symptoms even when they apparently lack major organ involvement or anemia. Because of the advanced age of the affected population, patients sometimes present with an exacerbation of another underlying medical condition, such as pulmonary, cerebrovascular, or coronary artery disease.
Some cases may present with chronic rhinitis secondary to nasal involvement of CLL cells.235 In rare cases, patients may present with a sensorimotor polyneuropathy associated with IgM antibody to various gangliosides.55 For unknown reasons, patients may note exaggerated responses to insect bites, particularly to those of mosquitoes.236,237
Patients who present with more advanced disease may experience weight loss, recurrent infections, bleeding secondary to thrombocytopenia, and/or symptomatic anemia. However, night sweats and fevers (the so-called B symptoms) are uncommon and should prompt evaluation for complicating infectious disease. Indeed, patients with CLL are more prone to viral or bacterial infections secondary to impaired T-cell immunity or hypogammaglobulinemia, respectively.
LYMPHADENOPATHY
Nearly 80 percent of all CLL patients have nontender lymphadenopathy at diagnosis, most commonly involving the cervical, supraclavicular, or axillary lymph nodes. Lymph node enlargement ranges from minimal to massive, the latter potentially causing local disfiguration or organ dysfunction. Some patients may develop symptoms of upper airway obstruction due to oral-pharyngeal lymphadenopathy. However, it is unusual for the lymphadenopathy in CLL to cause obstruction of vascular or lymphatic channels. Lymphedema of the extremities is rare, even in the setting of massive axillary and cervical adenopathy, and superior vena cava obstruction is so uncommon that it should alert the clinician to the possibility of a secondary pulmonary neoplasm. Computerized axial tomography of the abdomen can detect intraabdominal lymph node enlargement in a large number of patients. However, such information has yet to be incorporated into clinical staging schemes. Large retroperitoneal adenopathy can result in ureteral obstruction and hydronephrosis. Rarely, patients may develop periportal lymph node enlargement that results in biliary tract obstruction. Occasional patients may experience acute, painful swelling in previously nontender, chronically enlarged lymph nodes secondary to acute lymphadenitis resulting from infection with herpes simplex virus.238,239
SPLENOMEGALY AND HEPATOMEGALY
Approximately half of all CLL patients present with mild to moderate splenomegaly. Occasionally, this may cause symptoms of early satiety and/or abdominal fullness. Sometimes, splenic enlargement may result in hypersplenism, contributing to anemia and thrombocytopenia. However, in CLL such cytopenias are more commonly secondary to extensive marrow involvement with CLL and/or intermittent expression of autoantibodies.231,240,241,242 and 243 Less frequently, patients develop hepatomegaly secondary to leukemic cell infiltration of the liver. Derangement of hepatic function secondary to visceral involvement is usually mild, and cholestatic jaundice is unusual in the absence of nodal disease causing biliary tract obstruction.
EXTRANODAL INVOLVEMENT
Organ infiltration with leukemic cells is frequently detected at autopsy but is not commonly symptomatic. For example, leukemic cell infiltration of the renal parenchyma can be detected in over half of all patients examined postmortem. However, CLL only rarely is associated with impaired renal function. Leukemic cell infiltration, however, may become symptomatic when it develops in certain locations, such as in the retro-orbit, where it can produce proptosis. Lymph tissue also may develop in the scalp, subconjuctivae, prostate, gonads, or pharynx, the latter sometimes causing symptoms of upper airway obstruction. Infiltration of the pericardium by leukemia cells can produce a constrictive pericarditis244 or result in cardiac tamponade.245
Occasionally, the leukemic cells infiltrate the lung parenchyma, producing nodular or miliary pulmonary infiltrates that can be detected on chest x-ray. This may be associated with pulmonary function test abnormalities. The respiratory tract mucosa also may be involved. Leukemic infiltration of the pleura may result in hemorrhagic or chylous pleural effusions.246,247 and 248
The gastrointestinal tract also may be infiltrated with leukemic cells, causing abnormal mucosal thickening. This may result in ulceration, gastrointestinal bleeding, or malabsorption. The latter may cause dietary deficiencies of essential nutrients, such as folate. Finding iron deficiency should alert the physician to evaluate for gastrointestinal bleeding that may be due to mucosal ulcerations or to a secondary gastrointestinal malignancy.
Leukemic cell infiltration of the central nervous system is unusual but may produce headache, meningitis, cranial nerve palsy, obtundation, or coma.249 The development of neurologic changes in CLL, however, also may be caused by infections with unusual organisms, including fungi, Cryptococcus neoformans, Listeria monocytogenes, or other pathogens that generally only afflict an immune compromised host.
LABORATORY FEATURES
BLOOD FINDINGS
The diagnosis of CLL requires a sustained monoclonal lymphocytosis greater than 5000/µl (5 × 109/liter). At diagnosis, the absolute lymphocyte count generally exceeds 10,000/µl (10 × 109/liter) and is sometimes greater than 100,000/µl (100 × 109/liter). Morphologically, the leukemic cells generally appear similar to normal resting lymphocytes. Typically these cells have scanty, bluish cytoplasm upon Wright-Giemsa staining, moderately condensed and mature-appearing nuclei, and an MCV of 170 fl (see Plate XX-4). A few cells can have prominent nucleoli. During the preparation of the blood film, many CLL lymphocytes apparently are disrupted and appear as smudge cells. Leukemic leukocytosis in excess of 800,000/µl (800 × 109/liter) may produce blood hyperviscosity.
The red cells typically are normocytic and normochromic. About 15 percent of patients present with normocytic anemia. In the setting of extreme lymphocytosis, the packed red cell volume may be overestimated unless care is taken to exclude from the measurement the expanded buffy coat containing the leukemic cells. About 20 percent of all CLL patients have a positive Coombs’ test at some time during their disease due to the production of IgG anti-red cell autoantibodies by bystander nonleukemic B cells. Autoimmune hemolytic anemia, however, develops in only about 8 percent of CLL patients.
During the most advanced disease stage, patients have thrombocytopenia due to marrow replacement and hypersplenism. At any stage, however, patients can develop immune thrombocytopenia due to antiplatelet antibodies. Generally, the platelet morphology is not remarkable.
MARROW FINDINGS
The marrow invariably is infiltrated with leukemic cells. There are four patterns of marrow involvement.250,251 and 252 (Fig. 98-1). In approximately one-third of patients, the marrow has an interstitial, or lacy, pattern that is associated with a better prognosis and/or early-stage disease. About 10 percent of patients present with a nodular pattern of marrow involvement, and approximately 25 percent have a mixed nodular-interstitial pattern. These patterns also are associated with a better prognosis. A quarter of the patients present with extensive marrow replacement, producing a diffuse pattern that is associated with advanced clinical stage and/or more aggressive disease.252,253

FIGURE 98-1 Photomicrographs of marrow sections demonstrating (a) nodular, (b) interstitial, (c) mixed nodular and interstitial, and (d) diffuse patterns of infiltration. (Reproduced with permission from Pangalis GA, Roussou PA, Kittas C, et al.251)

LYMPH NODE FINDINGS
The lymph node architecture typically is effaced by a diffuse infiltration of small lymphocytes that have the same morphology as that of the circulating leukemic cells. The node histology is identical to that of low-grade small lymphocytic lymphoma. As the disease progresses, the nodes may coalesce and form large fixed masses. In rare cases, the lymph node can contain a few scattered cells that have the morphology and phenotype of Reed-Sternberg cells typically seen in Hodgkin disease (see Chap. 102).254
IMMUNOLOGIC STUDIES
Several tests are recommended as part of the laboratory evaluation of patients with CLL. Lymphocyte surface immunologic markers can determine monoclonality and the presence of CLL-type lymphocytes. The direct Coombs’ test can uncover those patients who have or are at risk for an immune hemolytic anemia. Measurement of serum immunoglobulin quantifies the depression of IgG, IgA, and IgM that predisposes to infection. Skin test with PPD and other recall antigens can detect anergy. The frequency of the concomitant T-cell functional defect increases in advanced stages of CLL.
IMMUNOPHENOTYPING
Flow cytometric analyses can evaluate leukemic cells for expression of B-cell or T-cell differentiation antigens, surface immunoglobulin, and k or l light chains. Such studies can distinguish B-cell CLL from not only T-cell leukemias but also other B-cell leukemias that can otherwise mimic B-cell CLL (Table 98-1). Useful markers for this are CD5, CD10, CD11c, CD19, CD20, CD22, CD23, CD25, CD38, and CD103 (see Chap. 13).151,255,256,257 and 258 The differential expression of these antigens helps to distinguish between the various B-cell leukemias (see Table 98-1). Analyses for other cell surface markers also may be clinically useful.

TABLE 98-1 IMMUNOPHENOTYPE OF CHRONIC B-CELL LEUKEMIAS/LYMPHOMAS

Cytoplasmic immunoglobulin can be detected in CLL B cells and may be a valuable adjunct in B-cell phenotyping.259 Compared to normal cells, CLL B cells have a lower density of surface but a higher content of cytoplasmic immunoglobulin. Rarely, intracytoplasmic inclusions of crystalloid immunoglobulin have been seen. Over three-fourths of patients with CLL may have excess light chains in the Golgi complex and the cisternae of the rough endoplasmic reticulum.260,261 and 262
PROTEIN ELECTROPHORESIS
The most common finding on serum protein electrophoreses is hypogammaglobulinemia. Nearly three-fourths of all B-cell CLL patients develop severe hypogammaglobulinemia during the course of their disease. Reduction in the serum levels of IgM precedes that of IgG and IgA. The degree of hypogammaglobulinemia correlates loosely with clinical stage, and virtually all patients with advanced disease have decreased concentrations of serum immunoglobulin.
However, 5 percent of patients have a serum monoclonal immunoglobulin paraprotein. The serum paraprotein generally is the same type as that present on the leukemic cell surface. When the concentration of IgM paraprotein is high, hyperviscosity may ensue, and the clinical picture can be confused with that of Waldenström macroglobulinemia (see Chap. 108). In some cases, there is defective and/or unbalanced immunoglobulin chain synthesis by the leukemic B-cell clone, resulting in mu heavy-chain disease and/or immunoglobulin light-chain proteinuria (see Chap. 109). The latter can be detected on urine immunoelectrophoresis (see Chap. 104).
When high-resolution agarose gel electrophoresis is combined with immunofixation, small paraprotein spikes can be identified in the sera or urine samples of nearly two-thirds of all patients.18,263,264 and 265 These paraprotein spikes generally have immunoglobulin heavy chains that belong to isotypes other than those expressed by the leukemic B-cell clone.18
DIFFERENTIAL DIAGNOSIS
The differential diagnosis of lymphocytosis is discussed in Chap. 87. Lymphocytosis can occur in persons infected with various viruses, Bordetella pertussis, or Toxoplasma gondii (see Chap. 87). However, the patients who usually encounter such illness generally are much younger than patients with CLL. Also, in contrast to the reactive lymphocytosis that occurs in response to these infections, the lymphocytosis of patients with CLL is persistent and monoclonal. The latter characteristic is important in distinguishing CLL from unusual cases of persistent polyclonal lymphocytosis of B cells that sometimes can masquerade as B-cell CLL.266,267 Flow cytometric analyses of blood mononuclear cells generally can differentiate between reactive lymphocytosis, polyclonal B-cell lymphocytosis, and monoclonal lymphocytosis secondary to lymphoproliferative disease.268
PROLYMPHOCYTIC LEUKEMIA
Prolymphocytic leukemia is a subacute variant of CLL in which over half of the blood leukemic cells are large lymphocytes, termed prolymphocytes. These cells can be distinguished from the leukemic cells in CLL by size and morphology.269 Prolymphocytes measure 10 to 15 µm in diameter, whereas CLL cells generally have the size of small resting lymphocytes (7–10 µm in diameter). Also, prolymphocytes in the blood or marrow have round or indented nuclei, each possessing a single prominent thick-rimmed nucleolus and chromatin that is more dense than that of a lymphoblast but less dense than that of a typical mature lymphocyte or a CLL B cell (see Plate XX-5). The cytoplasm generally is pale blue and agranular, except for occasional intracytoplasmic inclusions that are visible by electron, and sometimes light, microscopy.270 By scanning electron microscopy, these prolymphocytes often have more surface microvilli than do leukemic cells from patients with B-cell CLL. They may involve lymph nodes, generally producing a pseudonodular pattern of infiltration that is distinct from that of the diffuse pattern typical of CLL.271 In contrast to the leukemic B cells in CLL, prolymphocytes typically express high levels of surface immunoglobulin and stain brightly with SN8, a mAb specific for CD79b (see Chap. 13 and Chap. 83).272,273 These and other features that distinguish CLL from prolymphocytic leukemia are presented in Table 98-1. Other features of this disease are discussed in the section on prolymphocytic leukemia at the end of this chapter.
HAIRY CELL LEUKEMIA
The clinical and laboratory features that assist in distinguishing CLL from hairy cell leukemia and its variants, hairy cell leukemia variant, and splenic lymphoma with villous lymphocytes,274 are presented in Table 98-1. These diseases are discussed in Chap. 99.
The neoplastic B cells in hairy cell leukemia are larger than CLL cells (MCV 400 fl) and have more abundant cytoplasm, often with fine filamentous “hairy” projections (see Plate XX-7). These cells are strongly positive for tartrate-resistant isozyme 5 of acid phosphatase (TRAP) activity. Finally, in contrast to CLL B cells, the neoplastic cells in hairy cell leukemia express high levels of CD11c, the aX chain of the b2 integrins, and CD103, the aE subunit of the b7 integrins (see Chap. 99).
LYMPHOMAS
Lymphomas can have circulating neoplastic cells, sometimes producing a blood lymphocytosis that may be mistaken for CLL. The lymphomas are discussed in Chap. 103. Those lymphomas that most closely can resemble B-cell CLL are listed below.
SMALL LYMPHOCYTIC LYMPHOMA
Low-grade small lymphocytic B-cell lymphoma is closely related to B-cell CLL in its biology and clinical features. The neoplastic cells in small lymphocytic lymphoma with blood involvement are the same morphologically as the leukemic cells in CLL. Moreover, the histology of the involved lymph nodes in CLL and small lymphocytic lymphoma are indistinguishable.275 Similar to the B cells in CLL, the neoplastic B cells in small lymphocytic lymphoma frequently express immunoglobulins that bear autoantibody-associated cross-reactive idiotypes and that are encoded by nonmutated immunoglobulin genes.149,276 Finally, the neoplastic B cells in both diseases express many of the same surface antigens, including CD5.277 For these reasons, the distinction between these diseases is primarily clinical, in that CLL invariably is associated with a blood lymphocytosis (greater than 4000 lymphocytes/µl), whereas small lymphocytic lymphoma invariably is associated with lymph node involvement. Also, although patients with CLL invariably have marrow lymphocytosis, the marrow in small lymphocytic lymphoma need not be involved. When the marrow is involved, the pattern in small lymphocytic lymphoma typically is nodular, rather than interstitial or diffuse.252 This disorder is discussed further in Chap. 103.
MANTLE CELL LYMPHOMA
Mantle cell lymphoma (previously called centrocytic lymphoma, mantle zone lymphoma, or intermediate lymphoma) in the Working Formulation is an intermediate-grade B-cell lymphoma (see Chap. 96, Chap. 101, and Chap. 103). In contrast to the diffuse lymph node involvement typical in CLL, the histology of lymph nodes in mantle cell lymphoma typically is one of reactive germinal centers surrounded by well-defined, expanded mantle zones of monoclonal B cells.278 However, heavily involved lymph nodes may lose this architecture and appear diffusely infiltrated, assuming histology similar to that of lymph nodes involved in CLL.
The neoplastic B cells in mantle cell lymphoma express many of the same surface antigens as do CLL B cells, including CD5 (Table 98-1). However, in contrast to CLL B cells, mantle cell lymphoma cells generally do not express CD23. Mantle cell lymphoma cells also tend to express higher levels of CD79a than do CLL cells.279
LYMPHOMAS OF FOLLICULAR CENTER CELL ORIGIN
Low-grade lymphomas of follicular center cell origin also can involve the blood. There is often marked adenopathy and occasionally massive splenomegaly. The leukemic cells are small and typically have cleaved nuclei with well-delineated nucleoli. Follicular center small cleaved cell lymphomas frequently express the CD10 (CALLA) antigen. In contrast to CLL, these cells often express high levels of surface immunoglobulin and generally express neither mouse rosette receptors nor the CD5 antigen (Table 98-1). The cells are FMC7-positive. Biopsy of a lymph node will confirm nodular or diffuse small cleaved cell (poorly differentiated lymphocytic) lymphoma. These diseases are discussed in Chap. 103.
LYMPHOPLASMACYTIC LEUKEMIAS
Plasmacytoid lymphocytes can be seen on the blood films and are always present in the marrow of patients with Waldenström macroglobulinemia (see Chap. 108). These cells have abundant, often basophilic, cytoplasm with mature lymphoid nuclei. By flow cytometric analysis (see Chap. 81), these cells express pan-B lymphocyte surface antigens CD19, CD20, and CD24 (see Chap. 13) and are monoclonal as defined by immunoglobulin light-chain expression. Similar to CLL B cells, these cells often express CD5 and CD11b. However, they can be distinguished from CLL cells by their expression of the CD10 (CALLA) and/or CD9 antigens and by their lymphoplasmacytic morphology (see Chap. 96 and Chap. 101).
Patients with plasma cell myeloma may develop plasma cell leukemia. The leukemic cells can be distinguished from those in B-cell CLL by their plasmacytic morphology, their expression of CD38, PCA-1, CD56, and CD85, and their low-level or lack of expression of CD19, CD20, CD24, CD72, and HLA-DR (Table 98-1). Plasma cell myeloma is discussed in Chap. 106.
T-CELL CHRONIC LYMPHOPROLIFERATIVE DISORDERS
T-cell variants of CLL constitute a heterogeneous group of disorders that must be distinguished from B-cell CLL. T-cell chronic lymphoproliferative diseases are much less common. Several have counterparts in the various B-cell leukemias and are discussed in other chapters, including T-cell prolymphocytic leukemia (discussed in the section on prolymphocytic leukemia at the end of this chapter) and T-cell lymphoma (see Chap. 103). A subset of large granular lymphocytic leukemias represents another T-cell chronic leukemia that is discussed in Chap. 100.
These diseases can be distinguished from lymphoproliferative disorders of B cells or natural killer cells by immunophenotype. The leukemic cells from all T-cell malignancies lack expression of monoclonal surface immunoglobulin or B-cell restricted surface differentiation antigens, such as CD19 or CD20 (see Chap. 13), and generally lack immunoglobulin light-chain gene rearrangements (see Chap. 83). Characteristically, chronic T-cell leukemias have rearrangement and expression of the genes encoding the T-cell receptor for antigen (see Chap. 84) and express the CD3 surface antigens (see Chap. 13 and Chap. 84). The latter is a property exclusive to lymphocytes of the T-cell lineage and can be used to distinguish large granular lymphocytic leukemia of T-cell versus natural killer cell origin (see Chap. 100).
THERAPY, COURSE, AND PROGNOSIS
CLINICAL STAGING
Wide variability exists in the rate of disease progression and the incidence of disease-related complications among patients with CLL. Because of this, the life expectancies of patients with newly diagnosed CLL can vary tremendously. Staging helps to define prognosis and to decide when to initiate therapy.
Two major staging systems have been developed, each having established value in helping to predict survival.280 The first widely used system was introduced by Rai and colleagues in 1975.22 This staging system designated five clinical stages using Roman numerals 0 through IV. Patients in stages 0 and I have a favorable prognosis, while patients in stages III and IV have a relatively short survival (Table 98-2). The prognosis of patients in stage II is intermediate. Although confirmed to have useful predictive value,281 the number of stages was considered excessive by some investigators. Accordingly, in 1981, Binet and colleagues proposed a three-stage classification system that considered the total lymphoid mass.282 The most advanced stage, stage C, describes all patients who have anemia and/or thrombocytopenia due to impaired marrow function (Table 98-3). The remaining patients are divided into stages A or B, based upon the number of enlarged lymphoid areas (of which there are five: cervical, axillary, or inguinofemoral lymph nodes, and liver or spleen). Patients in groups A or B have less than three or greater than or equal to three areas of lymphoid enlargement respectively (Table 98-3). Most physicians use either the Binet or the Rai staging system. Generally, disease progression follows a stepwise pattern from earlier to later stages.

TABLE 98-2 RAI CLINICAL STAGING SYSTEM

TABLE 98-3 BINET CLINICAL STAGING SYSTEM

In 1987, Rai reorganized his original staging system into three categories: low-risk (stage 0), intermediate-risk (stages I and II), and high-risk (stages III and IV) patients.283 Low-risk patients have a projected median survival of greater than 150 months (Table 98-2). In contrast, intermediate- and high-risk patients have median survivals of approximately 90 months and 19 months respectively. Both the Binet classification and modified Rai classification have proven utility in helping to access disease outcome.283
OTHER PROGNOSTIC INDICATORS
In addition to the widely accepted staging systems of Rai and Binet, there are additional indicators that can help identify high-risk patients who may benefit from closer follow-up and/or early therapy. These variables could be considered when deciding whether to initiate therapy.
LEUKEMIC CELL DOUBLING TIME
CLL B cells generally do not have a high mitotic index and express low levels of the cyclin-dependent kinase inhibitor p27kip1 (p27), a protein that ordinarily increases as a cell progresses into S phase. However, some patients have leukemia cells that have high-level expression of p27.284 Such patients may have shorter blood lymphocyte doubling times and survival than average patients with CLL.
Patients whose lymphocyte counts double within 1 year have progressive disease, whereas those with stable counts represent a good-risk population. Independent of stage, the median survival for patients with a doubling time less than 12 months was 5 years, whereas it was greater than 12 years if the doubling time was greater than 12 months.285
MARROW HISTOLOGY
Biopsy can reveal characteristic patterns of marrow infiltration, defined as nodular, interstitial, mixed, or diffuse.286,287 (See Fig. 98-1). A diffuse replacement of the marrow is associated with a worse prognosis than a nodular or interstitial pattern.250,251 and 252,288 The marrow biopsy is more reliable than the aspirate is distinguishing patients with favorable disease (nodular and/or interstitial) versus nonfavorable disease (diffuse) independent of clinical stage.286 However, both the aspirate and biopsy appear to have independent prognostic value.286,289 As such, evaluation of the marrow is considered desirable, especially for patients prior to therapy.290
LEUKEMIA CELL PHENOTYPE
Atypical lymphocyte morphology is associated with a more adverse clinical course.291 If more than 50 percent of the leukemia cells have a prolymphocytic morphology, then the patient’s disease may have evolved to prolymphocytic leukemia.
A more adverse clinical course has been associated with leukemic cells that express CD38166 or that express only surface IgM rather than both IgM and IgD.292,293 Another study noted that advanced-stage disease was associated with low to nondetectable expression levels of CD11a and CD18 but had no significant relation to the relative expression of CD11c.175
KARYOTYPE
Survival of patients with abnormal karyotypes is significantly shorter than that of comparably staged patients with normal karyotypes.294,295 Multiple abnormalities in association with trisomy 12 carry a worse prognosis than trisomy 12 alone.56,294,296,297 However, patients who have trisomy 12 as the only cytogenetic abnormality fare worse than those with a normal karyotype or those with isolated abnormalities involving 13q14.298,299 Patients who have structural abnormalities of chromosomes 14, 6, or 11q– also generally have a more adverse clinical course than those with a normal karyotype.89,300 The prognostic effect of 11q deletion on survival is most apparent for patients younger than 55 years of age.
SERUM FACTORS
Provided the patient has normal renal function, there are several serum proteins that become elevated in patients with aggressive disease. Moreover, the relative level of each of these proteins has been found to correlate with the kinetics of tumor progression and/or tumor burden. For this reason, potential prognostic value can be obtained by measuring the relative serum levels of: beta-2 microglobulin (b2M),288,301,302 thymidine kinase (TK),303 soluble CD23,288,304,305 soluble vascular cell adhesion molecule-1 (sVCAM-1),306 or soluble CD27.183,307 Lactate dehydrogenase (LDH) also is generally elevated in patients with aggressive disease and in nearly all patients with Richter transformation.308,309 On the other hand, progressive disease more typically is associated with a greater suppression of T-cell function and a more marked decline in serum IgA.310 Hypercalcemia is rare in patients with CLL311 and may indicate Richter transformation312 (see below).
However, it should be recognized that certain treatments, diseases, or renal dysfunction could affect the relative level of each of these factors, mitigating their potential to have predictive value. This is evident, for example, in patients treated with granulocyte-macrophage colony-stimulating factor (GM-CSF).313 GM-CSF can induce substantial increases in the serum levels of b2M and TK that do not appear related to disease progression or impaired renal function.314
TELOMERASE ACTIVITY
Progressive shortening of chromosome telomeres occurs with repeated cell division and may result in cell senescence. Erosion of chromosome telomeres is prevented by telomerase, a ribonucleoprotein enzyme that synthesizes TTAGGG repeats on the ends of chromosomes using its RNA component as a template.315,316 Mean telomere lengths and telomerase activity have been correlated with survival in B-CLL.317 Mean telomere length is inversely correlated with telomerase activity. Leukemia cells with telomere lengths of less than 6.0 kb had high telomerase activity, whereas leukemia cells with telomere lengths of greater than 6.0 kb had low telomerase activity. Patients with leukemia cells that had high telomerase activity had a significantly shorter median survival than patients whose leukemia cells had low telomerase activity.
INDICATIONS FOR THERAPY
There are no proven cures for CLL. Moreover, treatment of early-stage patients with chemotherapy does not appear to offer any survival advantage over that achieved with conservative management.318 However, for certain patients therapy can reduce morbidity and/or improve survival significantly.
A number of criteria are useful for deciding when to initiate therapy (Table 98-4). Generally, an elevated blood lymphocyte count by itself is not an indication for therapy. Complications from extreme lymphocytosis, such as leukostasis, are rare in patients with nonprolymphocytic CLL who have blood lymphocyte counts below 800,000/µl.319 Also, minor or moderate lymphadenopathy in the absence of other indications is usually not treated. Lymphadenopathy that causes functional disturbances should be treated. Such disturbances include pain due to nerve impingement from nodal encroachment; obstruction of the small bowel, ureter, or upper airway; or extreme adenopathy causing cosmetic disfigurement.

TABLE 98-4 INDICATIONS FOR THERAPY IN B-CELL CLL

Newly diagnosed patients without the criteria listed in Table 98-4 should be followed monthly for the next several months. During follow-up exams, the hemogram should be monitored to access the rate of increase in the lymphocyte count and to evaluate for anemia or thrombocytopenia. Thereafter, patients with early-stage disease and good prognostic features should be followed at 2- to 6-month intervals without chemotherapy.
When the decision is made to initiate treatment, the objectives for therapy should be defined. Once the reasons for initiating chemotherapy are resolved, then treatment should be stopped, as there is no evidence that continued maintenance therapy improves survival.
Independent of the criteria listed in Table 98-4, patients who develop autoimmune hemolytic anemia (see Chap. 55), immune thrombocytopenia (see Chap. 117), or other pathologic autoimmune process warrant therapy appropriate for the autoimmune disease.
RESPONSE CRITERIA
In 1996, a National Cancer Institute–sponsored Working Group recommended criteria with which to describe the response to therapy in CLL.290 The definition of a complete response is largely clinical rather than biological. A patient has a complete response when he/she becomes free of clinical disease for at least 2 months. The patient must maintain a normal complete blood, with at least 1500 neutrophils, 100,000 platelets, and fewer than 4000 lymphocytes per µl of blood. The hemoglobin must be greater than 11 g/dl without requiring red cell transfusion. In addition, the patient must lack constitutional symptoms, hepatosplenomegaly, or detectable adenopathy. Finally, the marrow must contain fewer than 30 percent lymphocytes and lack lymphocyte nodules.
To classify as having a partial response, the patient must experience at least a 50 percent reduction in the number of blood lymphocytes and have at least a 50 percent reduction in lymphadenopathy or hepatosplenomegaly. In addition, one or more of the following criteria must be achieved and maintained for at least 2 months: platelets are greater than 100,000/µl, hemoglobin is greater than 11 g/dl, or a 50 percent improvement in platelet or red cell counts over pretreatment values without transfusions. Treated patients who fulfill all the criteria for a complete response but have persistent lymphocyte nodules in the marrow are classified as having had a nodular partial response.290
Progressive disease is defined by at least one of the following: increase greater than or equal to 50 percent in the absolute lymphocyte count or a transformation to a more aggressive histology; increase greater than or equal to 50 percent in the size of the liver and/or spleen or the new appearance of palpable hepatomegaly or splenomegaly; increase greater than 50 percent in the sum of the products of at least two lymph nodes (one of which must be greater than 2 cm) on two consecutive physical examinations performed 2 weeks apart; or the appearance of new palpable lymphadenopathy. Patients who do not achieve a complete or partial remission and who do not have progressive disease are defined as having stable disease.
SINGLE-AGENT CHEMOTHERAPY
GLUCOCORTICOIDS
Glucocorticoids are effective as single agents in CLL, especially for patients with autoimmune hemolytic anemia or immune thrombocytopenia (see Chap. 55 and Chap. 117). Even for nonautoimmune manifestations, prednisone, as a single agent, can control the disease temporarily in approximately 10 percent of patients.320 Generally, prednisone is given orally at a dose of 40 to 60 mg/day for 1 week and then tapered and stopped after another week. Thereafter, prednisone is given every month for 5 days at 60 mg/day.
Partial responses may be achieved by treatment with intravenous methylprednisolone at 1 g/m2/day for 5 days at monthly intervals for 7 months.321,322 Concomitant therapy with H2 antagonists and prophylactic antibiotics can reduce the rate of treatment-related complications, which also include fluid retention and hyperglycemia.
ALKYLATING AGENTS
Chlorambucil Since its introduction in 1952, chlorambucil (Leukoran) has been the main alkylating agent used for CLL. Although chlorambucil is useful in the palliative therapy of patients with advanced-stage disease, it does not appear to improve survival and should not be used for asymptomatic patients with early-stage disease.323
Given orally, it generally is well tolerated, without the side effects that sometimes may be seen with other alkylating agents, such as cystitis, alopecia, or gastrointestinal distress. There seems to be some sparing of the myeloid and megakaryocytic series. Generally patients are started on a daily oral dose of 2 to 4 mg. This can be advanced to 6 to 8 mg per day if the patient does not experience intolerable hematologic toxicity. Alternatively, patients can be treated intermittently with a total oral dose of approximately 0.4 to 0.7 mg/kg. This dose can be given on day 1 or divided into four equal daily doses and given on days 1 through 4. The cycle is repeated every 2 to 4 weeks, depending on the time to marrow recovery. Pulse chlorambucil is as effective as continuous administration and is less myelotoxic.320 Complete response rates of 15 percent and partial response rates of 65 percent are common.324
The effectiveness of chlorambucil for inducing apoptosis of leukemia cells in vitro can augmented by theophylline,325,326 and 327 a phosphodiesterase inhibitor that commonly is used to treat adult asthma. This suggests that there may be therapeutic advantage to administering both drugs simultaneously to patients with CLL. In a nonrandomized trial involving 12 patients with progressive disease, responses were noted in 11 cases at doses of chlorambucil that were 3- to 38-fold lower than that used in previous cycles.328
High-dose chlorambucil has been studied for patients with advanced-stage CLL.329 Chlorambucil was given for less than 6 months at a fixed dose of 15 mg per day until the patient achieved a complete response, or grade 3 toxicity. This treatment was noted in one single-institution study to effect a higher complete and partial response rate (89.5 percent) than that achieved with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) (e.g., six monthly cycles of doxorubicin at 25 mg/m2 on day 1, vincristine 1 mg/m2 on day 1, cyclophosphamide 30 mg/m2 per day, and prednisone 40 mg/m2 per day on days 1 to 5). However, significant myelotoxicity was observed.
Cyclophosphamide Cyclophosphamide is as active as chlorambucil in CLL.330 Patients can be started on daily oral doses of 50 to 100 mg. Alternatively, patients can be treated intermittently with 500 to 750 mg/m2 given intravenously or orally every 3 to 4 weeks, depending on the time to marrow recovery. Because intermittent or daily oral cyclophosphamide predisposes to hemorrhagic cystitis, it should be taken as a single dose in the morning rather than at bedtime. Patients should be encouraged to drink at least 2 to 3 liters of fluid per day.
DEOXYADENOSINE ANALOGS
Fludarabine Fludarabine (9-b-D-arabinofuranosyl-2-fluoradenine, F-ara-A) is a fluorinated monophosphate derivative of an adenosine analog that has significant activity in the treatment of CLL.331 Given as a 30-min intravenous infusion at a dose of 25 mg/m2 daily for 5 days at 4-week intervals, this drug can induce hematologic complete and partial responses in a high percentage of patients.332,333,334,335,336 and 337 An oral form of fludarabine has been developed that has good bioavailability and low intra-individual variation in its pharmacodynamics338 making it feasible to consider alternative dosing regimens.
Multicenter trials typically have observed overall response rates to parenteral fludarabine of approximately 45 percent, including 10 percent with complete responses, in previously treated patients. Furthermore, overall response rates of approximately 70 percent, including 38 percent with complete responses, are achieved when fludarabine is given as front-line therapy.339,340,341 and 342 Fludarabine, as a single agent, appears more effective in CLL than some combination chemotherapy regimens, such as CAP (cyclophosphamide 750 mg/m2 and doxorubicin 50 mg/m2 on day 1, and prednisone 50 mg/m2 per day on days 1 to 5).343,344 Moreover, remission duration appears significantly longer in patients achieving a response with fludarabine than in those who respond to such combination regimens.
Long-term follow-up studies indicate that even those patients who achieved complete response to fludarabine ultimately will have recurrent disease.342,345 The median time to progression of responders was 33 months for those who had not received prior chemotherapy, and 21 months for those who had. The median times to progression were 27 months for patients with a partial response and 30 to 37 months for those achieving a complete response.342 Although multicenter clinical trials have confirmed the activity of single-agent fludarabine in CLL,339,340 and 341 treatment of patients with this drug has not been shown to improve overall survival.
About one-third of patients who have not received prior therapy and nearly half of those who are refractory to treatment with chlorambucil will not achieve even a partial response to treatment with fludarabine. Logistic regression analysis in one study indentified four factors that were associated with poorer response to fludarabine: Rai stage III-IV disease, prior therapy, older age, and low albumin levels.346 In vitro drug-sensitivity testing using a differential staining cytotoxicity (DiSC) assay may have predictive value in identifying patients with fludarabine-response disease.347,348 In addition, patients who do not show evidence for a response to the first two cycles of therapy are unlikely to achieve a partial or complete response to subsequent cycles of treatment. For this reason, patients who fail to show any clinical benefit from two cycles of treatment should be considered for alternative types of therapy to minimize toxicity.
The major toxicities are hematologic and immunologic. Neutropenia is noted in approximately two-thirds of treated patients with advanced disease,335 although this usually is not dose-limiting. Patients also may experience reversible neurologic toxicity, even after receiving the standard dose of fludarabine.349 Highly responsive patients may experience the tumor-lysis syndrome.336,350,351
The major morbidity associated with fludarabine is immune suppression. Fludarabine produces a pronounced decrease in the number of blood T cells, especially CD4+ T cells, that often persists for more than a year after therapy.352,353 Treated patients apparently have an increased incidence of infection with opportunistic organisms, including herpes simplex, herpes zoster, Listeria monocytogenes, and Pneumocystis carinii.336,346,353
Patients treated with fludarabine have been noted to have an increased incidence of new-onset autoimmune diseases, such as autoimmune hemolytic anemia, immune thrombocytopenia, or pure red cell aplasia.344,354,355 However, it is controversial whether this defines a causal relationship. Tumor lysis syndrome can be another therapy-related complication.356,357 Finally, CLL patients treated with fludarabine also may develop transfusion-associated graft-versus-host disease,358,359 possibly reflecting the overall impairment to the host immune system that is induced by this drug. Despite the associated immune suppression, treatment with fludarabine does not appear to increase the risk for secondary malignancies in patients with CLL.360
2′-Chlorodeoxyadenosine (Cladribine) 2′-Chlorodeoxyadenosine (cladribine) is another deoxyadenosine analog that has activity in CLL361 (see Chap. 81). Different dosage schedules or administrations routes have proved effective, although the response rates do not appear to be better than those achieved with fludarabine. Monthly courses of cladribine given via intravenous infusion over 2 h at 0.12 mg/kg, daily for 5 consecutive days, has resulted in overall response rates of approximately 40 percent to 60 percent in patients who were previously treated with alkylating agents.362,363 and 364 Higher overall response rates are observed in previously nontreated patients. Although one study found that patients refractory to fludarabine still could respond to cladribine,365 a subsequent and larger study found that patients with advanced CLL refractory to fludarabine therapy were not likely to benefit from treatment with cladribine.366
Cladribine also appears effective when administered orally.367 Overall response rates of 75 percent were noted in previously non-treated CLL patients given cladribine at 10 mg/m2 per day orally for 5 consecutive days.368
Treatment with cladribine has not been shown to prolong survival. The median duration of partial remissions is approximately 9 months, and nonresponding patients have a relatively short median survival of approximately 4 months. DiSC assays347 have been reported to have predictive value in assessing a given patient’s potential response to therapy.369 However, the most evident predictor of a good response was a rapid decrease of blood lymphocyte counts following the first course of therapy. As with fludarabine, patients who fail to show any clinical benefit from two cycles of cladribine should be considered for alternative types of therapy to minimize toxicity.
The toxicities of treatment with cladribine are similar to those with fludarabine. Thrombocytopenia is a common dose-limiting toxicity, as is general myelosuppression. As with fludarabine, treated patients experience long-lasting reductions in the levels of blood T cells and have impaired cellular immunity to viral infections. Systemic fungal infections and opportunistic infections are a common cause of morbidity and mortality. There is one case report of a patient with refractory CLL who experienced the tumor-lysis syndrome following therapy with cladribine,370 although the incidence of this appears to be very low.
2′-Deoxycoformycin (Pentostatin) Deoxycoformycin (pentostatin) is a purine analog synthesized by Streptomyces antibioticus that structurally is related to adenosine.371 This drug inhibits adenosine deaminase, an enzyme important in lymphocyte purine metabolism (see Chap. 81). Pentostatin generally is administered intravenously at a dosage of 4 mg/m2 weekly for 3 weeks, then 4 mg/m2 every other week for 6 weeks and once a month for 6 months.371,372 This drug appears less effective in CLL than fludarabine or cladribine, effecting complete or partial responses in approximately 25 percent of patients.372 Since the toxicity of pentostatin is comparable to those noted for fludarabine or cladribine, it appears to offer no unique advantage for the treatment of CLL.
OTHER AGENTS
Cytosine Arabinoside High-dose cytosine arabinoside has modest activity in advanced-stage CLL.373 It is administered intravenously at a dosage of 3 g/m2 delivered over 2 h. This may be repeated one to three times every 12 h to complete one cycle.
Etoposide Patients who failed alkylator-based chemotherapy have been noted to achieve partial responses with oral etoposide, lasting 2 to 18 months.374 Etoposide was administered as a single drug at a dosage of 50 mg/m2 per day for 21 days in a 28-day cycle. Myelosuppression was the most common and serious dose-limiting effect.
Melarsoprol Melarsoprol, an organic arsenical compound used for treatment of trypanosomiasis, was noted to effect down-modulation of BCL-2 and induce apoptosis of CLL cells in vitro.375 Because of this, a clinical trial was conducted in which patients received escalating intravenous doses daily for 3 days, repeated weekly for 3 weeks, with doses of 1 mg/kg on day 1, 2 mg/kg on day 2, and 3.6 mg/kg on day 3 and on all days thereafter, up to a maximum daily dose of 200 mg.376 However, treatment was associated with significant central nervous system toxicity and limited clinical benefit.
COMBINATION CHEMOTHERAPY
CHLORAMBUCIL AND PREDNISONE
The standard regimen for treating patients who warrant the initiation of chemotherapy has been the combination of oral chlorambucil and prednisone. Each cycle consists of chlorambucil at 0.4 to 0.7 mg/kg on day 1, with prednisone at 80 mg per day on days 1 through 5. This course is repeated every 2 to 4 weeks, depending on the time to marrow recovery. The dosage of chlorambucil may be divided and given over 2 days. It is raised or lowered based upon the response and the degree of myelosuppression. When the white cell count declines below 10,000/µl the dose of chlorambucil should be reduced to maintain the white cell count between 5000/µl and 10,000/µl. The addition of prednisone to chlorambucil may provide a therapeutic advantage over chlorambucil alone.324 However, more recent studies have challenged this notion.377,378 Nevertheless, responses to the combination of chlorambucil and prednisone occur in about 80 percent (complete remissions in 15 percent plus partial remissions in 65 percent) of patients.320,379,380 and 381
FLUDARABINE-CONTAINING REGIMENS
Fludarabine/Cyclophosphamide (FC) Combinations of fludarabine, at 20 to 30 mg/m2 daily for 3 days, and cyclophosphamide, at 200 to 300 mg/m2 daily for 3 days, given every 28 days can result in favorable clinical responses in extensively pretreated patients.382 However, this combination does not appear to offer a significant response or survival advantage over single-agent fludarabine in previously nontreated patients. As such, this combination should only be considered as salvage therapy. Use of this combination is associated with a relatively high rate of nausea and vomiting (20 percent and 10 percent respectively) and skin rash. Myleosuppression can be severe and is a major dose-limiting toxicity.
Fludarabine/Mitoxantrone Treatment with fludarabine, given at 30 mg/m2 on days 1 through 3 of a 28-day cycle, along with mitoxantrone, given at 10 mg/m2 on the first day of each cycle, has achieved overall response rates of 80 percent in previously nontreated patients and 60 percent in patients who were refractory to therapy with alkylating agents.382 As such, this treatment may not provide for a significant advantage over that using single-agent fludarabine in previously nontreated patients. Its utility as salvage therapy is under investigation. Myelosuppression is the major dose-limiting toxicity.
Fludarabine/Cisplatin Cisplatin, administered at 100 mg/m2 via continuous intravenous infusion over 4 days, has been used in combination with fludarabine given at 30 mg/m2 via bolus intravenous infusion on days 3 and 4 of a 28-day cycle.383 These two drugs, alone or in combination with cytosine arabinoside at 500 mg/m2 on day 4 of the cycle, did not appear to offer significant benefit over that of single-agent fludarabine for the treatment of patients refractory to alkylating agents. Its use as a salvage regimen is under investigation. Myelosuppression is the major dose-limiting toxicity.
Fludarabine/Prednisone Concomitant use of prednisone with fludarabine does not improve the response rate but rather increases the risk for opportunistic infection, resulting in poorer outcome than use of fludarabine alone.342,346 Because of this, fludarabine/prednisone combinations are not recommended for patients with CLL.
Fludarabine/Chlorambucil Fludarabine has been used in combination with chlorambucil.350 Chlorambucil was given orally on day 1 at 15 or 20 mg/m2, and fludarabine was administered intravenously on days 1 to 5 at 10, 15, or 20 mg/m2, every 28 days. With chlorambucil at 15 mg/m2 given on day 1, the maximum tolerated dose for fludarabine was 20 mg/m2. Although responses were observed, treatment with this combination has not been shown to be significantly better than that with fludarabine alone.350
CLADRIBINE-CONTAINING REGIMENS
The response to cladribine in combination with cyclophosphamide and prednisone (CCP) has been evaluated in patients with CLL.384 Patients received cladribine at 0.1 mg/kg per day as a subcutaneous bolus injection on days 1 to 3 with intravenous cyclophosphamide 500 mg/m2 on day 1 and oral prednisone 40 mg/m2 on days 1 to 5 of a 28-day cycle for a maximum of six cycles. Overall response rates of 88 percent were observed, with 4 patients achieving a complete clinical and hematologic response and 12 achieving a partial response.
CYCLOPHOSPHAMIDE, VINCRISTINE, AND PREDNISONE
The combination of cyclophosphamide, vincristine, and prednisone (CVP) is effective in previously untreated patients and in some patients with refractory CLL.385 The dosages are cyclophosphamide 300 to 400 mg/m2, orally, daily for 5 days, vincristine 1 to 2 mg intravenously on day 1, and prednisone 40 mg/m2 orally per day for 5 days. The cycle is repeated every 3 to 4 weeks. About 25 percent of patients achieve a complete remission, and approximately 50 percent obtain a partial remission when treated with this regimen.385 No differences were noted in response rates or survival of CLL patients treated in randomized trials with either CVP versus chlorambucil and prednisone381 or chlorambucil alone.386
Patients previously treated with chlorambucil and prednisone may respond to CVP. Prolonged therapy over a 12- to 18-month period may prolong survival.379 In one series, Rai stages III and IV patients had a median survival of 4.2 years following 18 months of therapy, with the median survival of complete responders over 60 months. This may be compared historically with the 19-month median survival reported for stages III and IV patients in the mid-1970s.22 Therapy with cyclophosphamide, vincristine, and prednisone is associated with significant neurotoxicity and with more severe marrow toxicity than is therapy with chlorambucil and prednisone.
CYCLOPHOSPHAMIDE, DOXORUBICIN, VINCRISTINE, AND PREDNISONE
The addition of doxorubicin to CVP chemotherapy (CHOP) has been evaluated in patients with advanced CLL.387 These patients were treated with CVP, and half also received doxorubicin 25 mg/m2 on day 1. Adding doxorubicin to the chemotherapeutic regimen increased the median survival from less than 2 years to more than 4 years in one study. However, the mean survival of patients treated with CHOP was similar to that of patients who received CVP over an 18-month period. Vincristine does not appear to add substantially to the CHOP regimen. In a randomized multicenter clinical trial, patients with stage B or stage C CLL were treated with CHOP or with cyclophosphamide, doxorubicin, and prednisone without vincristine (CAP). The rates of partial response and overall response were, respectively, 64 percent and 75 percent for the CHOP-treated patients, and 65 percent and 72 percent for the CAP-treated patients.388 However, these response rates compare unfavorably with that of a third group of comparably staged CLL who were treated only with fludarabine, this group achieving partial or overall response rates in this same study of 75 percent and 94 percent respectively. This is consistent with other studies that show that fludarabine appears more effective as a single agent in CLL than these combination regimens.343
VINCRISTINE, DOXORUBICIN, AND DEXAMETHASONE
The regimen consisting of vincristine, doxorubicin, and dexamethasone (VAD) appears to have limited activity in CLL. In one study, patients received a 96-h infusion of 1.6 mg vincristine and 36 mg/m2 of doxorubicin and took 40 mg of dexamethasone orally each day for 4 days. This cycle was repeated every 3 weeks, inducing a 21 percent partial response rate and no complete responses.343
CYTOSINE ARABINOSIDE, CISPLATIN, AND ETOPOSIDE (ACE)
Combination therapy with cytosine arabinoside (4 doses at 2 g/m2 every 12 h), cisplatin (2 doses of 35 mg/m2 every 24 h), and etoposide (2 doses at 100 mg/m2) has induced partial responses and occasional complete responses in advanced-stage patients with refractory disease, sometimes inducing an acute tumor-lysis syndrome.389
SPLENECTOMY
Splenectomy may ameliorate the cytopenias associated with advanced-stage CLL, particularly thrombocytopenia.390,391 In one study, patients who underwent splenectomy for thrombocytopenia and/or anemia had a trend toward improved 3-year actuarial survival (31 percent ± 9 percent) over matched subjects who did not undergo splenectomy (12 percent ± 7 percent).391 Preoperative performance status appeared to be the best predictor of perioperative and postoperative survival.
RADIATION THERAPY
Systemic irradiation was the first therapeutic modality used in CLL that was found to effect some degree of patient improvement.10 However, it soon was recognized that the therapeutic benefit was short-lived and often resulted in severe marrow suppression.392
Irradiation remains a useful technique for localized treatment to ameliorate symptoms due to nerve impingement, vital organ compromise, painful bone lesions, or bulky disfigurement. Delivery of 200 Gy can result in rapid shrinkage of lymph nodes or masses.
Splenic irradiation is useful in patients with painful splenomegaly,393 especially in patients considered poor candidates for surgical splenectomy.394 Patients may experience systemic improvement after splenic irradiation, possibly due to irradiation of leukemic cells circulating through the spleen. However, the low rate of response and the short remission duration argue that splenic irradiation should be combined with other therapeutic approaches.395
Endolymphatic radiotherapy396 and extracorporeal irradiation of blood397 appear to provide limited improvement in lymphocyte counts but do not appear to improve patient survival. Extracorporeal photochemotherapy also has been tried in B-cell CLL but was found ineffective.398
LEUKAPHERESIS
Intensive leukapheresis may reduce organomegaly and improve hemoglobin and platelet levels.399 The measure has been advocated for patients with marrow failure who are refractory to standard therapy.400 This treatment has not been shown to improve patient survival.
INVESTIGATIONAL THERAPIES
MARROW OR BLOOD STEM CELL TRANSPLANTATION
Autologous Stem Cell Transplantation Several studies have examined the benefit of high-dose chemotherapy with stem cell rescue in patients with CLL (see Chap. 18). Complicating autologous stem cell transplantation (SCT) is the high probability that stem cell collections are contaminated with CLL cells, even in patients who have been treated to minimal residual disease.401,402 and 403 This has prompted investigation into more effective purging techniques to remove unwanted leukemia cells prior to transplantation. Nevertheless, a few studies with small numbers of patients have shown that complete clinical responses can be achieved in CLL.404,405 and 406 However, it is not yet known whether patients who have achieved complete responses in the setting of SCT have been cured of their disease.
Of some concern, however, are studies that identified trisomy 12 or 13q deletions in the CD34+ progenitor cells of the marrow or blood in a subset of patients with CLL.402,403 This suggests that patients with CLL might have CD34+ progenitor cells that harbor cytogenetic lesions that contribute to leukemia development. As such, eradication of the B cells that have differentiated from an aberrant pluripotent clone may not completely eliminate the risk for recurrent neoplastic transformation. Consistent with this are cases of recurrent CLL following high-dose therapy and autologous stem cell transplantation that have immunoglobulin gene rearrangements that were distinct from those of the original CLL clone.407
Allogeneic Stem Cell Transplantation Transplantation with allogeneic stem cells is being evaluated for younger patients with poor-prognosis CLL.408,409,410,411,412 and 413 Treatment-related morbidity rates in some series have been high, occurring in approximately half the treated patients.410 Autologous transplantation requires elimination of leukemia cells that invariably are found in the marrow following conventional treatments. Aggressive treatment may eradicate the leukemia cells to the levels that cannot be detected using sensitive PCR techniques to detect clonal immunoglobulin gene rearrangements.408 Patients who relapse following allogeneic marrow transplantation may respond to infusions of donor leukocytes, demonstrating the effectiveness of a graft-versus-leukemia effect.412,413 Collectively, these studies provide encouraging evidence that transplantation may be curative in a subset of patients with CLL.
“Mini” Allogeneic Stem Cell Transplantation Because patients who receive allogeneic cells appear to benefit from a graft-versus-leukemia response, some groups have treated CLL patients with nonmyeloablative doses of chemotherapy prior to allogeneic SCT. Khouri and colleagues414 treated 15 patients (median age 55; range 45 to 71 years) in this fashion, using a pretransplant regimen consisting of fludarabine and cyclophosphamide. Two to three months after transplant, the patients were infused with donor lymphocytes if they did not have graft-versus-host disease (GVHD) (see Chap. 18). Eleven patients had engraftment of donor cells, eight of which achieved a complete response. However, only 7 of the 15 treated patients (47 percent) were alive after a median follow-up of 180 days (range, 90 to 767 days), indicating that this approach is associated with a high mortality.
Another study examined allogeneic marrow transplantation for 15 CLL patients who were refractory to fludarabine.415 Three patients received a one- or two-antigen-mismatched graft, and the remainder received HLA-identical sibling donor grafts. Fourteen patients engrafted, and thirteen (87 percent) achieved a complete remission with a median follow-up of 3 to 60 months. These results are comparable to those observed after allogeneic marrow transplantation for CLL patients who had never been treated with fludarabine.
IMMUNOTHERAPY AND BIOLOGIC RESPONSE MODIFIERS
Cytokines
Recombinant interferon-a has been reported effective in patients with early-stage disease,416 inducing partial responses in about two-thirds of treated patients.417 This agent lowers the lymphocyte count with minimal side effects.418 In contrast, patients with advanced CLL may experience an acceleration of their disease when treated with higher doses of interferon.419
A clinical trial examined whether treatment of patients with human interleukin-6 (h-IL-6) for 5 days prior to CHOP chemotherapy could enhance leukemia-cell proliferation and response to chemotherapy. Of note, leukemia-cell expression of CD20 increased during the period of treatment with Rh-IL-6, raising the prospect of using Rh-IL-6 in combination with anti-CD20 monoclonal antibodies. However, Rh-IL-6 did not appear to enhance the proportion of leukemia cells in S phase, as assessed by labeling studies with bromodeoxyuridine or the observed response to CHOP chemotherapy.
Passive Immunotherapy Passive immunotherapy with monoclonal antibodies targeted to immunoglobulin idiotypes expressed by CLL cells have not resulted in significant therapeutic benefit.420 Infusion with anti-T101 (CD5), a murine monoclonal antibody, has shown transient beneficial effects, but modulation of the surface antigen by the target cells and allergic reactions to the murine antibody limited the usefulness of this approach.421,422 Phase I trials have been performed testing the safety of treating CLL with toxin-conjugated antibodies specific for CD19 (B4)423 or the CD25 (Tac)424 antigen.
Rituximab, IDEC-C2B8. Rituximab is humanized monoclonal antibody specific for human CD20.425 Infusion of this mAb at 375 mg/m2 per day for 4 days per cycle can induce responses in nearly half of patients treated with relapsed follicular lymphoma,426,427 possibly by directing antibody-dependent cellular cytotoxicity (ADCC) against CD20-bearing lymphoma B cells. However, CLL B cells express nearly tenfold lower levels of CD20 than most lymphoma cells and appear less sensitive to treatment with rituximab. Several clinical trials testing rituximab in CLL are ongoing. Nevertheless, some patients have experienced tumor-lysis syndrome following treatment with rituximab.428 Moreover, patients with leukemia cell counts exceeding 50 × 109/liter at the time of treatment have been noted to experience a severe cytokine-release syndrome secondary to release of tumor necrosis factor alpha (TNF-a) and interleukin-6 (IL-6).429 Elevated cytokine levels during treatment were associated with clinical symptoms, including fever, chills, nausea, vomiting, hypotension, and dyspnea. Lymphocyte and platelet counts dropped to 50 to 75 percent of baseline values within 12 h after the onset of the infusion. Simultaneously, there was a 5-fold to 10-fold increase of liver enzymes, D-dimers, and lactate dehydrogenase, as well as a prolongation of the prothrombin time. This complication may be mitigated by use of a fractionated dosing schedule with infusion of 50 mg rituximab on the first day, 150 mg on day 2, and the rest of the 375-mg/m2 dose on day 3.429
CAMPATH-1H. CAMPATH-1H is humanized monoclonal antibody-specific human CD52.430,431 and 432 This antibody binds to a surface antigen present on most lymphocytes, including CLL B cells, and can induce complement-mediated and antibody-dependent T-cell cytotoxicity. In one study, patients who were refractory to chemotherapy were given intravenous infusions of 30 mg CAMPATH-1H three times a week for 12 weeks.433 Of the 29 patients to receive such therapy, 38 percent experienced a partial remission, and 4 percent achieved a complete remission with median response duration of 12 months. CAMPATH-1H does not appear to have a significant impact on lymphadenopathy.
To minimize the “first-dose” reactions to intravenous CAMPATH-1H, such as fever, chills, and/or rash, CAMPATH-1H also has been administered subcutaneously at 30 mg three times per week for at least 6 weeks.431 Although partial remissions also were achieved, the duration of the response to CAMPATH-1H by either route is relatively short. Also, CAMPATH-1H treated patients appear to have an increased susceptibility to opportunistic infections (especially cytomegalovirus), possibly secondary to a further depletion of normal T-cells following treatment with this mAb.431,433 Moreover, responses appear to be short-lived and associated with an increased incidence of opportunistic infections. Nevertheless, CAMPATH-1H may be of value in eradicating residual disease prior to autologous transplantation for patients who have persistent disease after treatment with chemotherapy.433,434
Lym-1. Lym-1 is an IgG2a mouse mAb specific for human B cells that has been used in the radioimmune therapy of CLL.435,436 Conjugated with 131I, this mAb has been used in phase I/II trials in which patients received 131I-Lym-1 in escalating amounts from 1480 Mbq/m2 to 3700 Mbq/m2 (40 to 100 mCi/m2).437,438 For patients with splenomegaly, most of the administered radiolabeled antibody localized to the spleen and did not distribute uniformly through other lymphoid tissue. Nevertheless, the treatment was well tolerated and associated with reductions in spleen size and/or lymphocytosis. Although argued to possibly increase survival, the numbers of treated patients and duration of follow-up preclude definitive conclusions at this time.
GENE THERAPY
Infection of leukemia B cells with a replication-defective adenovirus vector encoding recombinant CD154 (Ad-CD154) induces expression of a variety of coreceptors, including CD54, CD58, CD80 (B7-1), CD86 (B7-2), and CD70, on both infected and bystander leukemia B cells, rendering such cells more proficient in presenting antigens to autologous T cells.222 Furthermore, Ad-CD154-infected CLL B cells can induce autologous T cells to generate cytotoxic T lymphocytes (CTL) in vitro specific for noninfected leukemia cells. This formed the basis for a clinical trial of gene therapy for CLL whereby leukemia B cell are transduced with Ad-CD154 ex vivo and then infused back into the same patient to induce host anti-leukemia-cell immune rejection.439
DISEASE COMPLICATIONS
INFECTION
Infection is major cause of morbidity and mortality in CLL.440 Patients often have an impaired antibody response to microbes and hypogammaglobulinemia, making them highly susceptible to recurrent infection. Streptococcus pneumoniae, Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, and the herpes zoster-varicella virus account for most infections, and the lungs, skin, and urinary tract are the sites most frequently affected.440 Fungal, mycobacterial, and cryptococcal infections are uncommon. However, as noted above, patients treated with purine analogs, such as fludarabine, apparently have an increased incidence of infection with other opportunistic organisms, including herpes simplex, cytomegalovirus, herpes zoster, Listeria monocytogenes, Pneumocystis carinii, and mycobacteria.336,346,353,441
Infections usually respond well to antibiotics in CLL patients with early-stage disease. However, at later stages, the response is less satisfactory and more often associated with systemic complications. For such patients it often is necessary to administer antibiotics for prolonged periods to eradicate soft-tissue or urinary tract infection. Patients may be immunized with nonviable vaccines, such as those used to immunize patients against influenza or S. pneumoniae. However, the response to immunization is often poor. The use of live vaccines is contraindicated due to the risk of the attenuated agent being virulent in the immunocompromised host.
Patients with advanced-stage disease, hypogammaglobulinemia, and low levels of specific antibodies to pneumococcal capsular polysaccharide appear to be at greatest risk for severe or multiple infections.442,443 Immunoglobulin deficiency is the factor that correlates best with the frequency, severity, and pattern of infection.440 For this reason, investigators have examined the utility of administering intravenous gammaglobulin at 400 mg/kg every 3 weeks to patients with severe hypogammaglobulinemia associated with recurrent infections. While such therapy may decrease the frequency of bacterial infections,444 it may not improve survival.445
SYSTEMIC AUTOIMMUNE DISEASE
CLL patients have an increased risk of autoimmune disease. Prednisone at a dosage of 1 mg/kg per day is used to treat autoimmune hemolytic anemia or immune thrombocytopenia and can be tapered slowly to the minimum dosage necessary. These diseases, and various treatment regimens for refractory disease, are discussed in Chap. 55 and Chap. 117.
For CLL patients who develop pure red cell aplasia presumed secondary to pathogenic autoantibodies, the combination of cyclosporine and prednisone appears superior to prednisone alone.446
SECOND MALIGNANCIES
Patients with CLL have an increased risk of second malignancies.440,447,448 The most frequent second tumors are melanoma, soft-tissue sarcoma, and colorectal and lung carcinoma. Multiple myeloma occurs at 10 times the expected rate in patients with CLL449 but evidently does not arise from the same malignant B-cell clone.450,451 and 452 Both untreated and treated CLL patients can develop acute myelogenous leukemia or myelodysplastic syndrome.453,454 The concurrence of AML or MDS and untreated CLL may represent two separate disease processes. Nucleoside analogs do not appear to enhance the risk for secondary malignancies.360 However, for some patients, alkylating agents may contribute to the development of second malignancy. In one large multicenter trial, patients with stage A CLL who were treated with intermittent chlorambucil had a poorer survival than that of a matched control group of untreated CLL patients, in part because they experienced a higher incidence of epithelial neoplasms.455
LEUKEMIA CELL TRANSFORMATION
CLL can undergo transformation into either of three disease entities, each of which has an adverse prognostic implication.
RICHTER TRANSFORMATION
In 1928, Maurice N. Richter described an aggressive lymphoma that developed in a patient with CLL.456 Now described as Richter transformation, this transition from an indolent leukemia to an aggressive, large B-cell, high-grade lymphoma can occur at any time in the course of CLL, occurring in approximately 3 percent of all patients at median interval of 2 years following the initial diagnosis of CLL.309,457
It is debated whether these lymphomas arise from the original CLL clone or from a de novo lymphoproliferation in the setting of CLL.458 However, nucleic acid sequence analyses of the immunoglobulin genes expressed by the original leukemic cells and the high-grade lymphoma of a patient with Richter transformation have provided irrefutable evidence that such lymphomas can arise from the original CLL clone.459 Some cases, however, may represent a genetically unrelated, independent second cancer. As noted, CLL patients with Richter transformation have a higher incidence of P53 mutations than do CLL patients with indolent disease,130 suggesting that cytogenetic abnormalities acquired in the course of CLL may generate a neoplasm with more aggressive growth properties.
The most common clinical and laboratory features associated
  

with Richter transformation (with their respective incidence indicated in parentheses) include: (1) elevation of serum lactate dehydrogenase (82 percent); (2) rapid lymph node enlargement (64 percent); (3) systemic symptoms of fever and/or weight loss (59 percent); (4) a monoclonal gammopathy on serum protein electrophoresis (44 percent); and (5) extranodal disease (41 percent).309 Patients also may have abdominal symptoms due to increasing hepatosplenomegaly or neurologic symptoms secondary to central nervous system involvement.460,461 and 462 Occasional patients may present with an extranodal mass lesion.463 Patients with Richter transformation often have bulky retroperitoneal adenopathy and massive splenomegaly.
The diagnosis of Richter transformation requires lymph node biopsy. Involved lymph nodes are effaced by large immunoblastic cells with abundant basophilic cytoplasm and irregular nuclei with prominent nucleoli.275 The marrow may be infiltrated with these immature cells, sometimes resulting in osteolytic lesions. Descriptions of the lymphoma cells in tissue vary from what the Working Formulation currently describes as either small noncleaved cell lymphoma, large-cell lymphoma (cleaved or noncleaved), or large-cell lymphoma with tumor giant cells.457,460,461,464 All these types are considered high-grade lymphomas in both the Working Formulation and the Kiel classification (see Chap. 101) and are distinguished readily from the small lymphocytic lymphoma that typifies the tissue phase of CLL.275
The treatment for patients with Richter transformation is similar to that used for patients with high-grade lymphoma (see Chap. 103). Although occasional patients have achieved long-term remissions following intensive multiagent chemotherapy,462 most patients at best achieve only a partial remission and have a very poor prognosis. Overall, patients with Richter transformation have median survival of 5 months from diagnosis.309
CLL/PLL AND PROLYMPHOCYTIC TRANSFORMATION
In nearly 15 percent of B-cell CLL patients, the population of leukemic cells consists of a mixture of small lymphocytes and prolymphocytes, the latter cell type accounting for between 10 to 50 percent of the lymphoid cells.465,466 These patients have been termed to have CLL/PLL, although this term is not in frequent use. These patients have a degree of lymphadenopathy and age distribution similar to that of patients with CLL but more pronounced splenomegaly. In 80 percent of CLL/PLL cases, the proportion of prolymphocytes remains stable, and survival does not differ from that of CLL patients with comparable clinical-stage disease.467 Such patients generally do not have blood prolymphocyte counts above 15,000/µl or massive splenomegaly.
The remaining patients with CLL/PLL will undergo a prolymphocytic transformation. This is characterized by a decrease in the proportion of leukemic cells able to form rosettes with mouse erythrocytes, increases in the proportions of blood lymphocytes with prolymphocyte morphology and immunophenotype, and progressive splenomegaly. One study noted the leukemic cells in transformation apparently acquired the t(6;12) translocation that commonly is associated with prolymphocytic leukemia.468 Patients with this transformation respond poorly to chemotherapy, and survival is limited. In one study, the mean survival of patients after transformation to prolymphocytic leukemia was 9 months.469
ACUTE LYMPHOBLASTIC LEUKEMIA
Very rarely, patients with B-cell CLL may develop acute lymphoblastic leukemia.470 Studies of a few of the dozen cases reported indicate that the acute leukemia can arise from the same B-cell clone as that of the CLL cells.471,472,473 and 474 Blastic transformation has been associated with a seven- to eightfold increase in the expression of C-MYC and immunoglobulin genes.474 Leukemic blast cells generally express terminal deoxynucleotidyl transferase (TdT) and high levels of surface immunoglobulin and HLA-DR.
PROGNOSIS
There are no established cures for CLL, and spontaneous remissions are extremely rare.475,476 Nevertheless, the prognosis can vary substantially between different patients, depending upon clinical stage and the presence or absence of disease features that have been associated with disease progression and/or a more adverse clinical outcome (see section on clinical staging).
Patient age had been argued to be an independent prognostic factor.298,308,477,478 However, a large study from the U.S. National Cancer Data Base revealed that the 5-year relative survival was 69.5 percent, 72.2 percent, 63.1 percent, and 41.7 percent for age groups under 40, 40 to 59, 60 to 79, and 80+ years respectively, indicating that the 5-year survival does not vary significantly between these different age groups.1 As such, it appears that CLL, and not comorbid disease, caused the greatest percentage of deaths, even among the aged.
Another study also found that younger and older patients have a similar overall median survival probability but had different distributions of causes of deaths.479 CLL-unrelated deaths and secondary malignancies predominated in the older age group, whereas the direct effects of leukemia were prevalent in the younger age group. At diagnosis, younger and older patients displayed a similar distribution of clinical features, except for a significantly higher male/female ratio in younger patients (2.85 versus 1.29; p less than 0.0001). Both groups had an elevated rate of second malignancies (8.3 percent versus 10.7 percent), whereas the occurrence of Richter syndrome was significantly higher in younger patients (5.9 percent versus 1.2 percent; p less than 0.00001). Two subsets of young CLL patients with a different prognostic outcome could be identified. One group, comprising 40 percent of the patients under age 55, had long-lasting stable disease without treatment and an actuarial survival probability of 94 percent at 12 years from diagnosis. The remaining patients had progressive disease and a median survival probability of 5 years after therapy.479 A key feature of patients with the more adverse prognosis is evidence for disease progression.480
B-CELL PROLYMPHOCYTIC LEUKEMIA
HISTORY AND DEFINITION
B-cell prolymphocytic leukemia (PLL) is a clinical and morphologic variant of CLL that first was described as a distinct entity in 1973.481 It is a subacute lymphoid leukemia with an incidence that is about 10 percent that of CLL. The diagnosis of prolymphocytic leukemia requires that at least 55 percent of the circulating leukemic lymphocytes have a prolymphocytic morphology.465 Such cells are larger than resting lymphocytes and have a high nucleocytoplasmic ratio, a basophilic cytoplasm devoid of granules, moderately condensed chromatin, and a single prominent nucleolus. In 80 percent of such cases, the prolymphocytes are neoplastic B cells,482 whereas the remaining cases are derived from mature T cells.
ETIOLOGY AND PATHOGENESIS
The etiology is unknown. There is a 4:1 male to female predominance, suggesting that males are much more susceptible to developing this disease. Also, B-cell prolymphocytic leukemia can evolve from B-cell CLL.466 As such, factors that contribute to the pathogenesis or progression of CLL may operate in B-cell prolymphocytic leukemia.
CYTOGENETICS
The karyotype of the leukemia cells from many patients displays the 14q+ abnormality.483 Trisomy 12 is another recurrent abnormality.484,485 Deletions of the long arm of chromosome 6 (6q–) and rearrangement affecting chromosomes 1 and 12 are occasionally observed. One study observed a t(6;12)(q15;p13) chromosomal anomaly in several independent cases, leading the investigators to postulate that this anomaly is distinctive for a subset of patients with prolymphocytic leukemia.468 The (2;13)(q35;q14) translocation that commonly is associated with pediatric rhabdomyosarcoma also has been identified.486
Loss of heterozygosity at 17p13.3 associated with inactivating mutations in the P53 gene is observed in as many as three-quarters of the cases examined.487,488 The high frequency of P53 mutations in B-cell prolymphocytic leukemia is in marked contrast to what is observed in B-cell CLL and may explain the relative resistance of this disease to therapy. In addition, some cases of B-cell prolymphocytic leukemia have t(2;8) translocations involving the C-MYC gene that are similar to those observed in Burkitt lymphoma (see Chap. 103).489 Such mutations may account for the aggressive clinical course of prolymphocytic leukemia relative to that of B-cell CLL.
CYTOGENESIS
B-cell prolymphocytic leukemia is derived from mature B cells that have undergone immunoglobulin gene rearrangement (see Chap. 83). These cells invariably have monoclonal immunoglobulin gene rearrangements and express many of the same B-cell surface antigens as do leukemic cells in CLL. In many cases, the disease may evolve from preexistent CLL. The immunoglobulins expressed by prolymphocytic leukemia cells frequently bear autoantibody-associated cross-reactive idiotypes, suggesting a biased use of immunoglobulin variable region genes similar to that of leukemic cells in B-cell CLL.490 However, sequence analyses indicate the prolymphocytic leukemia cells from at least half of the patients express nonmutated variable region genes, whereas the remaining cases express mutated variable region genes.491 The presence of such somatic mutations suggests that the B-cell PLL cells from at least some individuals may be derived from a postgerminal center B cell (see Chap. 5 and Chap. 83).
CLINICAL FEATURES
Over 50 percent of the patients are over 70 years of age at diagnosis. Presenting symptoms include fatigue, weakness, weight loss, an acquired bleeding tendency, or early satiety with abdominal discomfort due to splenomegaly. Splenomegaly is massive in nearly two-thirds of the patients. The liver also may be enlarged. Nevertheless, patients typically have minimal palpable lymphadenopathy.
In rare cases, patients may present with leukemic meningitis,492,493 leukemic pleural effusion,494 or malignant ascites.495 A few patients develop cardiopulmonary complications due to leukostasis associated with extreme leukocytosis.496
LABORATORY FEATURES
Over three-fourths of the patients have blood lymphocyte counts greater than 100,000/µl.271,277 The marrow commonly is infiltrated diffusely with neoplastic prolymphocytes. At autopsy, these cells can be found to have infiltrated most other organs.484 At presentation, patients commonly have a normochromic and normocytic anemia, with blood hemoglobin less than 11 g/dl and/or blood platelet counts below 100,000/µl. As in CLL, patients commonly have hypogammaglobulinemia.497 However, many patients have a monoclonal gammopathy on serum protein electrophoresis.
Prolymphocytic leukemia B cells express B-cell differentiation antigens similar to those of B-cell CLL. However, expression of CD5 is variable.465 Even in cases that have evolved from CD5+ CLL B cells, the leukemia cells have low to negligible expression of CD5 (see Table 98-1). Also, in contrast to CLL B cells, prolymphocytic leukemia cells generally express very high levels of surface immunoglobulin, usually IgM with or without IgD498 and react strongly with the antibody FMC7. In addition, prolymphocytic leukemia cells generally express high levels of CD22 and often are negative for CD23. Finally, in contrast to CLL B cells, prolymphocytic leukemia B cells generally stain brightly with SN8, a mAb specific for CD79b (see Chap. 13 and Chap. 83).272,273
THERAPY, COURSE, AND PROGNOSIS
At presentation, patients commonly have advanced-stage disease that requires treatment. Most patients present with prominent splenomegaly and hyperleukocytosis and have rapid progression soon after diagnosis. Nevertheless, some patients may have a more indolent course.499 As such, the indications for therapy are similar to those used for patients with CLL. These include disease-related symptoms, symptomatic splenomegaly, progressive marrow failure, or a blood prolymphocyte count of more that 200,000/µl.
Treatments for patients with prolymphocytic leukemia are similar to those described for patients with CLL. Alkylating agents similar to those used in CLL are commonly used. However, chlorambucil or cyclophosphamide, in combination with prednisone and/or vincristine, typically yield response rates of less than 20 percent.465 Treatment with high-dose glucocorticoids appears less effective for patients with prolymphocytic leukemia than for those with CLL.322 Partial and complete responses have been observed in approximately half the patients treated with intensive combination chemotherapy regimens similar to those used to treat high-grade lymphomas (see Chap. 103), such as CHOP. Unfortunately, responses are relatively short-lasting. Although occasional patients may respond to salvage regimens,500,501 the long-term survival is generally poor.
The deoxyadenosine analogs are active in this disease. Cladribine given at 0.1 mg/kg per day for 7 days by continuous infusion every 28 to 35 days has been noted to induce complete and partial remission in approximately half of the patients with de novo B-cell prolymphocytic leukemia.502,503 and 504 Similarly, fludarabine at a dose of 30 mg/m2 over 30 min daily for 5 days every 4 weeks produced complete and partial remissions in nearly 40 percent of the patients treated.505 In another study, the response rates to fludarabine were similar to that noted for B-cell CLL.351 Rapid response to fludarabine may be complicated by the tumor-lysis syndrome.506,507
Pentostatin also appears effective, although less so than fludarabine. Twenty patients with prolymphocytic leukemia were treated with pentostatin (2′-deoxycoformycin) at a dosage of 4 mg/m2 intravenously once a week for 3 weeks, then every other week for three doses. The major hematologic toxicity of this regimen was thrombocytopenia. Although 45 percent achieved a partial remission, no patients achieved a complete response. The median duration of the remission was 9 months. Patients with B-cell prolymphocytic leukemia had a higher rate of response and duration of remission (12 months) than those with disease of T-cell origin.508 However, pentostatin also has some activity in T-cell prolymphocytic leukemia.509
Splenectomy may ameliorate symptoms, but only transiently.390 Splenic irradiation, with 1000 to 1600 Gy delivered to the splenic bed, has been advocated as a primary therapy for this disease.510,511 especially for symptomatic patients who are considered poor candidates for chemotherapy and/or splenectomy.512
Case reports indicate that interferon-a can be effective in inducing cytoreduction in prolymphocytic leukemia.513,514 and 515 There is one report of a patient who achieved a 5-year survival following a complete response to interferon-a following splenic irradiation.516 However, generally interferon-a appears less effective than chemotherapy.
Spontaneous remissions are extremely rare.517
T-CELL PROLYMPHOCYTIC LEUKEMIA
DEFINITION AND HISTORY
In 1989, the French-American-British (FAB) Cooperative Group distinguished five subgroups of T-cell leukemia, namely T-cell CLL; T-cell prolymphocytic leukemia; human T lymphotropic virus type I-positive (HTLV-I+) adult T-cell leukemia/lymphoma; and Sézary syndrome.518 When a new entity called large granular lymphocytic leukemia was defined (see Chap. 100), the existence of T-cell CLL as a distinct entity became a topic of debate.519,520,521 and 522 Because of this the World Health Organization commissioned a panel of experts to draft a new classification of the hematologic neoplasms.523 At a meeting in November 1997, this panel proposed a categorization of peripheral T-cell neoplasms that largely was based on the Revised European-American Lymphoma classification, or REAL classification524 (see Chap. 101). However, because of its aggressive clinical behavior, T-cell CLL was reclassified under the heading of T-cell prolymphocytic leukemia, without regard to subtle differences in morphology.525 Even together they account for less than 5 percent of all chronic lymphoid leukemias.
ETIOLOGY AND PATHOGENESIS
The etiology is unknown. There is a 3:2 male to female predominance, suggesting that males are more susceptible to developing this disease.
Infection with human T lymphotropic virus type I (HTLV-I) has been speculated to play a role in the development of at least some cases of T-cell prolymphocytic leukemia. Evidence for HTLV-I can be found in the leukemia cells of patients with T-cell prolymphocytic leukemia, suggesting a causal relationship.526 However, another study involving 36 patients with T-cell prolymphocytic leukemia from an area that was nonendemic for HTLV-I failed to reveal any evidence for HTLV-I or human T lymphotropic virus type II (HTLV-II) DNA or transcripts in the leukemia cells.527 As such, the association of HTLV-I and T-cell prolymphocytic leukemia cells may be coincidental in areas with high rates of HTLV-I infection. Alternatively, there may be multiple mechanisms involved in leukemogenesis, some involving HTLV-I in endemic areas.528
Consistent with this hypothesis, the cytogenetic features of T-cell prolymphocytic leukemia appear to vary depending upon the patient population studied. In the United States and Europe, inv(14q), del(11q), translocations involving 11q23, i(8q), trisomy 8q, and rearranged Xq28 are the commonest nonrandom chromosomal abnormalities in T-prolymphocytic leukemia.529 Moreover, abnormalities of the short arm of chromosome 12 are often observed.530 In contrast, chromosome 14 and 8 abnormalities are infrequently noted in the T-cell prolymphocytic leukemia cells of Japanese patients,531 suggesting that T-cell prolymphocytic leukemia is a heterogeneous disorder.
ATAXIA-TELANGIECTASIA MUTATED GENE
Patients with ataxia-telangiectasia have a high risk of developing T-cell prolymphocytic leukemia. Ataxia-telangiectasia is an autosomal recessive disorder characterized by cerebellar ataxia, oculocutaneous telangiectasia, immune deficiency, genome instability, and predisposition to malignancies, particularly T-cell neoplasms. The responsible gene, called ataxia-telangiectasia mutated (ATM), maps to chromosomal region 11q22.3-23.1, is 150 kb in length, consists of 66 exons, and encodes a nuclear phosphoprotein of approximately 350 kDa.93 Patients with ataxia-telangiectasia (A-T) frequently develop clonal expansions of T-cells that often progress to T-cell prolymphocytic leukemia, suggesting that ATM is a predisposing factor. Furthermore, inactivating mutations in ATM frequently are observed in both alleles of T-prolymphocytic leukemia cells from patients who do not have ataxia-telangiectasia.532,533 and 534 Moreover, ATM mutations appear associated with T-cell prolymphocytic leukemia and are infrequent in other T-cell malignancies, such as T-cell ALL.535 These findings suggest that ATM functions as a tumor-suppressor gene in T-cell prolymphocytic leukemia.
T-CELL LEUKEMIA 1 AND RELATED GENES
Studies of t(X;14)(q28;q11) chromosomal rearrangements in T-cell prolymphocytic leukemia have implicated two additional genes, designated MTCP1 or TCL1, in the pathogenesis of this disease.529,536,538 These genes encode two homologous proteins, designated p13(MTCP1) and p14(TCL1), with highly similar tertiary structure539 that often are dysregulated in T-cell prolymphocytic leukemia. In addition, clonal T-cell expansions similar to that of T-cell prolymphocytic leukemia that develop in patients with ataxia-telangiectasia also frequently have aberrant expression of these genes and/or harbor translocations involving the 14q32.1 or Xq28 regions, where the TCL1 and MTCP1 are located.537 Finally, mice transgenic for MTCP1 under the control of CD2 regulatory elements spontaneously develop T-cell leukemias that share many features in common with T-cell prolymphocytic leukemia.540 As such, the proteins encoded by these genes may play an important role in the pathogenesis of this disease.
CLINICAL FEATURES
Presenting symptoms include fatigue, weakness, weight loss, and early satiety with abdominal discomfort due to splenomegaly.519,522,541 On presentation, patients generally have blood lymphocyte counts in excess of 10 × 103/µl, marrow infiltration, and splenomegaly. In contrast to B-cell prolymphocytic leukemia, lymphadenopathy is a common finding in T-cell prolymphocytic leukemia.
About a third of patients have cutaneous involvement on the torso, arms, and face, which generally is present at the time of diagnosis.542 Skin manifestations include a diffuse infiltrated erythema; infiltration localized to the face and ears; nodules; and erythroderma, producing a nonscaling, papular, nonpruritic rash. Some cases present with a cutaneous infiltration mimicking a cellulitis that is resistant to antibiotic therapy.543
LABORATORY FEATURES
Biopsy of erythematous skin lesions generally shows a perivascular or periappendageal dermal infiltrate of lymphoid cells with a prolymphocytic morphology.542
Neoplastic T cells invariably can be found infiltrating the marrow, often in an interstitial pattern, with varying degrees of involvement.
The leukemia cells express the T-cell differentiation antigens CD2, CD3, CD5, and CD7, but not CD1, HLA-DR, or terminal transferase, reflecting a mature T-cell phenotype (see Chap. 13 and Chap. 84). In over 75 percent of cases the leukemia cells have a helper T-cell phenotype as they express CD4 but not CD8.544 About 15 percent of cases have leukemia cells that express CD8 but not CD4.519,525,545 In less than 10 percent of the cases, the leukemic T cells express both CD4 and CD8,546 a less mature phenotype implying derivation from a more primitive T cell (see Chap. 5 and Chap. 82). Monoclonal gene rearrangements in the genes encoding the a and b chains of the T-cell receptor can be detected in the leukemia-cell genomic DNA (see Chap. 84).
DIFFERENTIAL DIAGNOSIS
The lymphocytosis of T-cell prolymphocytic leukemia can be distinguished readily from that of B-cell leukemias by immunophenotypic analyses (see section on differential diagnosis for CLL).
POLYCLONAL T-CELL LYMPHOCYTOSIS
T-cell prolymphocytic leukemia should be distinguished from other lymphoproliferative processes that can present with T-cell lymphocytosis (see Chap. 87), such as the reactive T-cell lymphocytosis that can occur in infectious mononucleosis (see Chap. 90). Lymphocytosis due to polyclonal T-cell expansion generally consists of both CD4+/CD8– and CD4–/CD8+ T cells and lacks clonal T-cell receptor gene rearrangements (see Chap. 84). Southern analyses for T-cell receptor gene rearrangements or evaluation for expression of T-cell receptor variable region genes can help distinguish T-cell prolymphocytic leukemia from this entity.
LARGE GRANULAR LYMPHOCYTIC LEUKEMIA
The leukemic cells in this disorder have the distinctive morphology of large granular lymphocytes (see Chap. 96 and Chap. 100). These cells have abundant cytoplasm that contains many azurophilic granules. Two major subtypes are defined. In the more common type, the leukemic cells are derived from the T-cell lineage and generally express the CD3 surface antigen. This disorder formerly was called Tg-CLL. In the other subtype, the leukemic cells are derived from natural killer cells and lack expression of CD3. These diseases are discussed in Chap. 100.
ADULT T-CELL LEUKEMIA/LYMPHOMA
Adult T-cell leukemia/lymphoma is endemic to the southwest of Japan and the Caribbean region. Most patients have lymphadenopathy, hypercalcemia, and high white blood cell counts. Skin involvement, lytic bone lesions, and hepatomegaly are common. The leukemic cells have polylobed or convoluted nuclei. The diagnosis can be confirmed by demonstration of antibodies to HTLV-I. It is an aggressive disorder with short survival and is discussed in Chap. 103.
MYCOSIS FUNGOIDES AND SÉZARY SYNDROME
Cutaneous T-cell lymphomas (Sézary syndrome and mycosis fungoides) have a helper CD4+ T-cell phenotype and often have blood involvement. This disease is discussed in Chap. 103.
Sézary-cell leukemia (SCL) is a mature T-cell leukemia with characteristic cerebriform nuclei, whereas Sézary syndrome (SS) involves a mature T-cell lymphoma with a similar nuclear morphology. However, the distinction between T-cell prolymphocytic leukemia and Sézary-cell leukemia is not straightforward. The leukemia cells in either disease can have similar immune phenotypes and cytogenetic abnormalities.547 Moreover, clinical manifestations are similar, as is the overall clinical course. This has led some investigators to consider Sézary-cell leukemia as a variant form of T-cell prolymphocytic leukemia.547,548
T-CELL CLL
The major feature distinguishing T-cell CLL from T-cell prolymphocytic leukemia was the morphology of the leukemia cells.522 However, because T-cell CLL and T-cell prolymphocytic leukemia share so many other clinical and laboratory features, the distinction of T-cell CLL as a separate entity is currently not considered to have clinical utility. Instead, more attention should be given to distinguishing T-cell prolymphocytic leukemia with the usual CD4+/CD8– phenotype from exceptional cases of T-cell prolymphocytic leukemia/T-cell CLL that have a CD4–/CD8+ phenotype, generally lack prolymphocytic morphology, and have an even more aggressive clinical course than typical T-cell prolymphocytic leukemia.525,545
THERAPY, COURSE, AND PROGNOSIS
The disease is aggressive and generally refractory to conventional alkylator-based chemotherapy, with a median survival of about 7.5 months.549
Treatment with deoxyadenosine analogs yields higher response rates, although it has not been determined whether these drugs provide a survival benefit. Two articles describe treatment of T-cell PLL with cladribine.550,551 Pentostatin given intravenously at 4 mg/m2 weekly for the first 4 weeks and then every 2 weeks until maximal responses is effective in inducing complete or partial responses in about half of patients with T-cell prolymphocytic leukemia.509
Patients with extensive cutaneous involvement may benefit from treatments that commonly are used for mycosis fungoides, such as topical corticosteroids, mechlorethamine, carmustine, ultraviolet light B, PUVA, or total skin electron beam (TSEB) therapy.552 These treatments are discussed in Chap. 103. However, systemic therapy is warranted for patients with T-cell prolymphocytic leukemia, and this generally obviates local therapy.
The humanized monoclonal antibody specific for CD52, CAMPATH-1H, causes significant T-cell depletion when used to treat patients with B-cell CLL. Because of this, it is being evaluated for use in patients with T-cell prolymphocytic leukemia. In one study of 15 patients, 11 (73 percent) treated with CAMPATH-1H had major responses, compared with 40 percent with pentostatin. Complete remissions were documented in nine (60 percent) of the CAMPATH-1H-treated cases, and only three (12 percent) were obtained with pentostatin.553 Treatment with CAMPATH-1H can result in complete remissions, even in patients with large tumor burdens and high blood leukemia cell counts.554
Treatment of patients with T-cell prolymphocytic leukemia with high-dose chemoradiotherapy and allogeneic stem cell transplantation from HLA-matched sibling donors has resulted in anecdotal success.555
COURSE AND PROGNOSIS
In one large study, median survival was 3 years for patients with prolymphocytic leukemia and 8 years for those with CLL.467 Patients with T-cell prolymphocytic leukemia, however, may have an even poorer prognosis than those with B-cell prolymphocytic leukemia and have a median survival of only approximately 7 months.556,557 and 558 However, some patients may experience an initial indolent clinical course with stable moderate leukocytosis.559 Also, it is not certain how these survival times may improve with the advent of monoclonal antibody therapy and other new modalities of treatment for this disease.