Long term outcome of patients with hairy cell leukemia treated with pentostatin

Hodgkin Lymphoma and Hairy Cell Leukemia Arising from Chronic Lymphocytic Leukemia: Case Reports and Literature Review

Richter’s syndrome represents the progression of chronic lymphocytic leukemia (CLL) to more aggressive diseases, most frequently diffuse large B-cell lymphoma, while Hodgkin’s lymphoma (HL) and hairy cell leukemia (HCL) are rarely described. The first case involved a 67-year-old man with a diagnosis of a high-risk stage-II CLL treated with rituximab and ibrutinib, developed a HL nodular sclerosis variant after three months of therapy for CLL. After achieving a complete remission for HL and ibrutinib cessation because of drug-related cardiotoxicity, the patient relapsed after five months off-therapy and died due to disease progression after two cycles of brentuximab-vedotin. The second case involved an 83-year-old female with a diagnosis of stage-IV CLL treated with rituximab plus bendamustine who developed a HCL eight years later. Pentostatin was unsuccessfully employed as upfront HCL therapy, and the patient was then switched to rituximab while in remission for CLL. In conclusion, Richter’s transformation risk rate might be higher in patients treated with novel targeted therapies, and multiparametric flow cytometry and lymph node biopsy at relapse could help in early identifying small clones. The treatment of predominant neoplasia is mandatory, and disease-specific drugs are administered; however, clinical efficacy might be lower in these patients.

The pharmacological management of hairy cell leukemia

INTRODUCTION

Hairy cell leukemia (HCL) is a B-cell lymphoid malignancy that accounts for approximately 2% of all leukemias. Treatment with purine nucleoside analogs (PNA) results in a high response rate and remains the standard of care. Long term follow-up shows that most patients relapse and require retreatment. Newer combination strategies and agents have emerged to try to reduce the relapse rate and to address cases of PNA refractoriness.

AREAS COVERED

The authors reviewed the literature on the pharmacological management of HCL, including recent studies that led to new agents being incorporated into practice.

EXPERT OPINION

Combination of cladribine plus rituximab produces a high rate of measurable residual disease-negative complete remission. In our center, newly diagnosed patients are offered cladribine followed by 8 weekly doses of rituximab in an ongoing phase II trial. Patients in first relapse are also offered this combination if they were initially treated with a single-agent PNA, or if the remission duration was ≥5 years after first-line cladribine plus rituximab. Patients who relapse within 5 years are offered therapy with a novel agent that may include the BRAF inhibitor vemurafenib, alone or in combination with rituximab, dabrafenib in combination with trametinib, the BTK inhibitor ibrutinib, or moxetumomab pasudotox.

How I manage patients with hairy cell leukaemia

Patients with hairy cell leukaemia (HCL) have highly favourable outcomes after purine analogue therapy. However, most patients subsequently relapse and require re-treatment. A minority of patients develop purine analogue-refractory disease. Targeted therapies have improved outcomes for such patients. Recently, the BRAF V600E mutation was identified in most patients with classical HCL, resulting in constitutive mitogen-activated protein kinase pathway activation; impressive responses are achieved in heavily pre-treated patients with BRAF inhibition. The CD22-targeted immunoconjugate moxetumomab pasudotox and BTK inhibitor ibrutinib also achieve responses in relapsed and refractory patients. HCL variant and the IGHV4-34 molecular variant of HCL lack BRAF mutation and have inferior outcomes with standard purine analogue therapy. The addition of rituximab to purine analogues achieves very high rates of minimal residual disease-negative complete remission and improves outcomes for patients with HCL variant. Given the rarity of HCL, optimal integration of novel therapies into treatment algorithms will require well-designed, collaborative studies.

My treatment approach to hairy cell leukemia

Hairy cell leukemia (HCL) is a rare chronic lymphoproliferative disorder characterized by circulating B cells with cytoplasmic projections, pancytopenia, splenomegaly, and a typical flow cytometry pattern. Recently, the BRAF V600E mutation was uniformly identified in one HCL series, which may provide insights into the pathogenic mechanisms. The disease course is usually indolent but inexorably progressive. Patients require treatment when they have significant cytopenia or occasionally recurrent infections from immunocompromise. In the mid-1980s, interferon replaced splenectomy as the initial treatment. A few years later, 2 purine nucleoside analogs, cladribine and pentostatin, showed promising activity in HCL. Complete response rates approached 95% with cladribine given as a single 7-day intravenous infusion. Newer methods of cladribine administration and modified dosing schedules have since been studied. Pentostatin response rates are comparable. We generally prefer cladribine because of its ease of administration, single infusion schema, and favorable toxicity profile. Since the introduction of these drugs, which have never been randomly compared, long-term follow-up studies have confirmed impressive and durable response durations. However, roughly 40% of patients with HCL eventually relapse. In this setting, patients can be re-treated with purine analogs. Rituximab also has a reasonable response rate in relapsed HCL; it can be given as a single agent sequentially after purine nucleosides or concurrently. Immunotoxins have robust responses but remain in development. Targeting the BRAF pathway will be an exciting future area of research. Many patients have minimal residual disease after initial treatment, but the clinical significance of this remains unknown.

Infectious complications in hairy cell leukemia

The natural history of hairy cell leukemia (HCL) includes frequent and potentially life-threatening infections. Prior to the development of effective therapy, the incidence in patients followed for several years was as high as 60%, with infection as a prime cause of death in patients. Studies of the immune system of patients with HCL identified several potential reasons, including profound neutropenia and monocytopenia. In addition, treatment including chemotherapy and splenectomy further compromised the immune system. The success of new therapies has changed the frequency and severity of infections in patients with HCL. During the initial phase of treatment, however, infection risk remains high, with incidence ranging from 30 to 50%. Attempts to ameliorate the risk with growth factors in conjunction with treatment have not been successful, but lower doses of drugs and/or combination therapy have been tried with reported success. In the majority of patients, successful therapy results in normalization of the neutrophil count and marked reduction in the severity and frequency of infections. Interestingly, after purine nucleoside treatment, there is profound depression of CD4+ cells without development of the opportunistic infections seen with patients with human immunodeficiency virus (HIV). Studies to reduce morbidity and mortality should focus on initial induction regimens, as well as confirming the long-term benefit of treatment on risk of infection.

Hairy-cell leukemia variant: recent view on diagnosis, biology and treatment

Hairy-cell leukemia variant (HCl-V) is a district clinico-pathological entity with intermediate features between classical HCl (HCl-C) and B-cell prolymphocytic leukemia. HCl-V is now included in the World Health Organization (WHO) classification as a provisional entity. It is an uncommon disorder accounting for approximately 0.4% of chronic lymphoid malignancies and 10% of all HCl cases. In contrast to HCl-C, HCl-V is a more aggressive disease and according to the new WHO classification it is no longer considered to be biologically related to HCl-C. Patients with HCl-V have an elevated white blood count, easy-to-aspirate bone marrow and weak reactivity to tartrate - resistant acid phosphatase (TRAP). Immunophenotypically, HCl-V cells are positive for CD103 and CD11c and negative for CD25. The HCl-V cells express also the B-cell antigens, CD19, CD20 and CD22. The HCl-V patients have frequently an unmutated Ig gene configuration. Currently, the principles of therapy for this rare disease derive from uncontrolled single institutional studies, or even single case reports. In contrast to HCl-C, the HCl-V response to purine nucleoside analogs (PNA) is limited to partial responses in approximately 50% of patients. However, complete responses were observed in patients treated with rituximab and anti-CD22 immunotoxins. In Japan, a distinct subtype of HCl known as HCl-Japanese variant (HCl-JV) has been identified. As with HCl-V, patients with HCl-JV have leukocytosis, weak TRAP activity in leukemic cells, and lack of CD25 antigen. In this review, the biology, diagnostic criteria, and current therapeutic options in HCl-V and HCl-JV are presented.

Approach to the patient after relapse of hairy cell leukemia

The current hairy cell leukemia (HCL) treatment is excellent, but evidence of cure with purine analogs cladribine and pentostatin, is lacking. Significant long-term immune suppression, particularly to CD4+ T-cells, and declining complete remission rates with each course, make the identification of new therapies an important goal. The anti-CD20 monoclonal antibody (Mab) rituximab displays significant activity, and, while causing prolonged normal B-cell depletion, spares T-cells. Recombinant immunotoxins, containing an Fv fragment of a Mab fused to truncated Pseudomonas exotoxin, have shown efficacy in HCL resistant to both purine analogs and rituximab. LMB-2 targets CD25 and can induce remission providing the HCL cells are CD25+. All HCL cells display CD22. Recombinant anti-CD22 immunotoxin BL22, targeting CD22, has shown significant efficacy in phase I and II testing, and avoids prolonged suppression of both normal B- and T-cells. An improved high-affinity version of BL22, termed HA22, is currently undergoing phase I testing.

Hairy cell leukemia

Progress in the treatment of patients with hairy cell leukemia (HCL) has led to a significant change in the natural history of the disease. With current regimens, the majority of patients achieve a complete remission, and their survival curves are similar to those for appropriate age-matched individuals without the disease. At the same time, new technologies are allowing better understanding of the molecular mechanisms responsible for the pathogenesis of this and other indolent lymphoid neoplasms. Several studies using modern techniques with different sensitivities have demonstrated the persistence of minimal residual disease (MRD) after therapy with nucleoside analogues in majority of patients. However, it is not clear whether such MRD would invariably lead to leukemia recurrence or what level of MRD can predict relapse. The role of monoclonal antibodies, naked or conjugated with toxins, in the management of HCL and their ability to eradicate MRD is under investigation. Whether such strategies of chemoimmunotherapy would lead to further improvements in the outcome of patients with HCL needs to be further investigated.

Current status of older and new purine nucleoside analogues in the treatment of lymphoproliferative diseases

For the past few years more and more new cytotoxic agents active in the treatment of hematological malignancies have been synthesized and become available for either in vitro studies or clinical trials. Among them the class of antineoplastic drugs belonging to the purine nucleoside analogues group (PNAs) plays an important role. Three of them: pentostatin (DCF), cladribine (2-CdA) and fludarabine (FA) were approved by Food and Drug Administration (FDA) for the treatment of hematological malignancies. Recently three novel PNAs: clofarabine (CAFdA), nelarabine (ara-G) and forodesine (immucillin H, BCX-1777) have been synthesized and introduced into preclinical studies and clinical trials. These agents seem to be useful mainly for the treatment of human T-cell proliferative disorders and they are currently undergoing clinical trials in lymphoid malignancies. However, there are also several studies suggesting the role of these drugs in B-cell malignancies. This review will summarize current knowledge concerning the mechanism of action, pharmacologic properties, clinical activity and toxicity of PNAs accepted for use in clinical practice, as well as new agents available for clinical trials.

Chapter 2: Ring-Expanded (‘Fat‘) Purines and their Nucleoside/Nucleotide Analogues as Broad-Spectrum Therapeutics

This chapter describes a family of ring-expanded purines, informally referred to as “fat” or f-purines, as well as their nucleoside/nucleotide analogues (RENs/RENTs) that have broad applications in chemistry, biology, and medicine. Although purine itself has never been found in nature, substituted purines, such as adenine and guanine, or their respective nucleoside derivatives, adenosine and guanosine, are the most ubiquitous class of nitrogen heterocycles and play crucial roles in wide variety of functions of living beings As nucleotides (AMP,GMP), they are the building blocks of nucleic acids (RNA/DNA). They serve as energy cofactors (ATP, GTP), as part of coenzymes (NAD/FAD) in oxidation-reduction reactions, as important second messengers in many intracellular signal transduction processes (cAMP/cGMP), or as direct neurotransmitters by binding to purinergic receptors (adenosine receptors). Therefore, it is not surprising that the analogues of purines have found utility both as chemotherapeutics (antiviral, antibiotic, and anticancer agents) and pharmacodynamic entities (the regulation of myocardial oxygen consumption and cardiac blood flow). While they can act as substrates or the inhibitors of the enzymes of purine metabolism to render their chemotherapeutic action, their ability to act as agonists or antagonists of A1/A2A receptors is the basis for the modulation of pharmacodynamic property.

Hairy cell leukemia: current concepts

Hairy cell Leukemia (HCL) is a chronic lymphoproliferative disorder that was characterized in the late 1950s. HCL is defined, according to the WHO classification, as a mature (peripheral) B-cell neoplasm (1). HCL accounts for between 2-3% of all leukemia cases, with about 600 new cases diagnosed in the U.S. each year (1). HCL occurs more commonly in males, with an overall male to female ratio of approximately 4:1. The median age of onset is 52 years. This disease is seen more commonly in Caucasians and appears to be especially frequent in Ashkenazi Jewish males, with rare occurrence in persons of Asian and African descents (1). Hairy cells are distinct, clonal B cells arrested at a late stage of maturation. They are small B lymphoid cells that possess oval nuclei and abundant cytoplasm with characteristic micro-filamentous ("hairy") projections. They strongly express CD103, CD22, and CD11c (2). These cells typically infiltrate the bone marrow, the spleen, and to a lesser extent the liver, lymph nodes, and skin. Many patients present with splenomegaly and pancytopenia. Other clinical manifestations include recurrent opportunistic infections and vasculitis. Historically, HCL was considered uniformly fatal (2). However, recent treatment advances, using purine analogues such as Cladribine and Pentostatin, led to a significant improvement in prognosis with achievement of high response rates and durable remissions (2).

Pentostatin: impact on outcome in hairy cell leukemia

Major advances in the management of patients who have hairy cell leukemia have been made following the use of purine nucleoside analogs. Pentostatin and cladribine are equally effective, and have impressive long-term effectiveness. Although the degree of myelosuppression may be less with the use of pentostatin, this may reflect differences in the schedule and dose of drug administration between these agents. The gradual, but relentless, improvement in the peripheral blood counts enables out-patient management with pentostatin in most patients. Cladribine affords the convenience of a single course of administration. A direct comparative study with these two agents is unlikely to yield the optimal management of patients who have minimal residual disease following the administration of either agent is warranted in the context of a clinical trial. Patients do relapse, and the overall survival curves have not reached a plateau, which indicates that cure has not been secured. The satisfaction of having improved the outcome for patients who have this previously untreatable leukemia should not give way to complacency for further improvement in the management of this disease. Future studies should be directed to optimizing the therapy for minimal residual disease as well as clearer definition of supportive care.

Hairy cell leukemia

Hairy cell leukemia is a rare B-cell neoplasm. When treated with either pentostatin or cladribine, complete and durable remissions can be secured and life expectancy for most patients is normal. A small minority of patients require alternative treatment with monoclonal antibodies or immunotoxins. Patients who attain a complete response to first-line treatment have the best prognosis.

Current treatment options in hairy cell leukemia and hairy cell leukemia variant

Hairy cell leukemia (HCL) is a chronic B-cell lymphoproliferative disorder characterized by splenomegaly, pancytopenia and circulating lymphocytes displaying prominent cytoplasmic projections. HCL has usually an indolent course and the patients with asymptomatic disease do not require therapy. Treatment of progressive symptomatic HCL includes a variety of pharmacological approaches such as interferon-alpha (IFN-alpha), pentostatin (DCF) and cladribine (2-CdA), which have significantly improved the disease prognosis. 2-CdA and DCF seem to induce a similar high response rate and a long overall survival. They are also active in relapsed patients. More recently high activity of anti-CD20 monoclonal antibody (rituximab) and anti-CD25 (LMB-2) and anti-CD22 (BL-22) immunotoxins have increased the number of therapeutic options for HCL. Splenectomy may be still indicated in patients with massive, symptomatic splenomegaly or results in severe cytopenia. IFN-alpha may have a place in patients with very severe cytopenia, in HCL in pregnancy and in patients who have failed prior therapy with purine nucleoside analogs. HCL variant (HCL-V) is a distinct clinico-pathological entity which seems to be resistant to IFN-alpha and purine nucleoside analogs - DCF and 2-CdA. However, preliminary observations suggest that monoclonal antibodies - rituximab and BL-22 immunotoxin are highly active in this disorder even refractory to 2-CdA. In this review current therapeutic strategies in HCL and HCL-V are presented.

Chronic lymphoid leukemias other than chronic lymphocytic leukemia: diagnosis and treatment

The World Health Organization classification divides lymphoid malignancies into precursor B-cell and T-cell neoplasms as well as mature B-cell and T-cell neoplasms. Mature B-cell neoplasms comprise more than 85% of non-Hodgkin lymphomas worldwide and can be further subclassified according to the postulated cell of origin by using specific morphologic, immunophenotypic, and molecular characteristics. Similarly, the more uncommon mature T-cell neoplasms have been better characterized to include numerous distinct entities with widely varying natural histories. The distinction between lymphoma and leukemia is somewhat arbitrary and is based on variable involvement of the bone marrow, peripheral blood, and lymphatic system. In this article, we review the diagnostic and clinical features of mature B-cell and T-cell lymphoproliferative disorders that commonly have a leukemic presentation.

Infections associated with purine analogs and monoclonal antibodies

Nucleoside analogs and monoclonal antibodies are commonly used to treat lymphoproliferative disorders and have become established as the treatment of choice in chronic lymphocytic leukemia, hairy cell leukemia, and follicular lymphomas, as well as a number of other malignant lymphoid neoplasms. When used in standard doses, these agents have a low incidence of extramedullary side effects resulting in their inclusion in a number of combination regimens. The most important complications associated with these drugs are myelosuppression, immunosuppression and infections. This is further accentuated when they are used in combination with other drugs such as alkylating agents. Several investigators have attempted to delineate the risk factors predicting the risk of infections associated with these agents. Furthermore, risk-based strategies to decrease the incidence of these infectious complications have been proposed.

Towards the pharmacotherapy of hairy cell leukaemia

Hairy cell leukaemia (HCL) offers one of the few examples of rapid progress in the development of effective treatments for chronic lymphoproliferative disorders. After the first description of HCL as a separate disease in 1958, splenectomy was the treatment of choice, but rarely resulted in remission of disease and had scarce benefit on survival. In 1984, IFN-alpha became the first agent able to significantly modify the prognosis of HCL by inducing high response rates and long-term remissions. More recently, purine analogues have significantly further increased the percentages of remissions, with a reduced risk of relapse and are now generally used as first-line treatment. Monoclonal antibodies targeting CD20, CD22 and CD25 antigens, have also shown responses for resistant or relapsing disease. This article will review the current treatment strategies for HCL.

Hairy cell leukemia: survival and relapse. Long-term follow-up of purine analog-based therapy and approach for relapsed disease

Since its initial description approximately 50 years ago, there has been an impressive evolution in therapies for hairy cell leukemia. Long-term follow-up with 2-cholorodeoxyadenosine and 2'-deoxycoformycin demonstrates that both agents result in a high complete remission rate and overall survival. Relapse rates appear to be between 20% and 30%. Therapeutic strategies for patients with relapsed disease include retreatment with a purine analog, rituximab, or the anti-CD22 pseudomonas exotoxin A immunoconjugate, BL-22.

Long remissions in hairy cell leukemia with purine analogs

BACKGROUND

Both pentostatin and cladribine have efficacy in hairy cell leukemia (HCL), but it is not known which agent achieves better results.

METHODS

We reviewed a series of 219 patients with HCL, with median follow-up from diagnosis of 12.5 years (range 1.0 -34.6 yrs), treated with either pentostatin (n = 185) or cladribine (n = 34), to compare these agents and assess the potential for cure.

RESULTS

Overall response to pentostatin was 96% with a complete response (CR) in 81% and a median disease-free survival (DFS) of 15 years. Response to first-line cladribine was 100% with a CR in 82% and DFS of 11+ years. The relapse rates at 5 years and 10 years were 24% and 42%, respectively, with pentostatin, and 33% and 48% with cladribine. Survival at 10 years was respectively 96% and 100%. CR rates decreased with each sequential relapse through 69% to 45% (P < or = 0.001). Patients achieving CR after first-line treatment had a significantly longer DFS (P = 0.00007) than those achieving a partial response; a similar result was seen after second-line therapy (P = 0.00001). DFS also declined with sequential treatment (P = 0.00005).

CONCLUSION

We have shown equivalent efficacies for both agents in the treatment of HCL, with DFS showing no plateau. True cure in HCL remains elusive, but the addition of monoclonal antibodies may be beneficial. Our results suggest that achieving CR should remain the main goal of treatment.

Pentostatin (Nipent) in the treatment of chronic lymphocyte leukemia and hairy cell leukemia

Pentostatin (Nipent), formerly known as deoxycoformycin, is a profound inhibitor of the enzyme adenosine deaminase, resulting in the accumulation of metabolites that inhibit ribonucleotide reductase, which in turn inhibits DNA synthesis. Pentostatin was the first of the purine analogs to undergo extensive testing as an anticancer agent and the first to receive US Food and Drug Administration approval for a treatment indication. It is highly effective as first-line monotherapy in hairy cell leukemia, with a complete response rate of 80% and a 10-year survival rate of around 80%. Pentostatin is also active in chronic lymphocyte leukemia as a single agent, but appears even more promising in combination approaches with the alkylating agents chlorambucil or cyclophosphamide. Due to the increasing recognition of delayed severe stem cell and immune suppression following therapy with other purine analogs, there has been renewed interest in pentostatin, especially in combination with chemotherapy and/or the monoclonal antibody rituximab (Rituxan) in chronic lymphocyte leukemia.

Pentostatin in the treatment of hairy-cell leukemia

Pentostatin (2'-deoxycoformycin; Nipent), a potent inhibitor of adenosine deaminase, is a purine nucleoside analogue that is highly effective in the treatment of hairy-cell leukemia. This agent is capable of inducing durable complete remissions in the majority of patients, and is capable of re-inducing a complete remission in many of the patients who have relapsed. Pentostatin appears to have changed the natural history of this disease. Long-term follow-up studies suggest that patients with hairy-cell leukemia who are induced into complete remission have a projected survival comparable to age-matched controls. While purine nucleoside analogues induce profound T-cell dysfunction and longstanding immunosuppression, the incidence of secondary malignancies is apparently not increased. Infections still pose a threat to these patients, and effective strategies for treating this disease that do not further compromise the immune system are needed. Patients with this disease should be encouraged to participate in ongoing clinical trials to better define the optimal treatment regimen. New studies should explore the combination of pentostatin and rituxan in treating the typical form of hairy-cell leukemia, and the incorporation of new agents for those with the rare variant form of this disease.

Advances in the treatment of hairy-cell leukaemia

Hairy-cell leukaemia (HCL) is an uncommon B-cell chronic lymphoproliferative disorder that accounts for about 2% of all leukaemias. Although the disease is generally indolent in its natural course, the majority of patients require treatment for life-threatening infections due to pancytopenia or symptomatic splenomegaly. During the past 20 years, remarkable progress has been made in the treatment of HCL. Since the introduction of interferon-alpha, splenectomy, which was formerly the standard therapy, has been rarely used. With the purine analogues cladribine and pentostatin, response rates are even better than with interferon-alpha and long-lasting remissions can be achieved in most patients. Therefore, these agents are now considered the treatment of choice. Recently, immunotherapeutic approaches which use monoclonal antibodies have increased the number of therapeutic options for HCL and offer promising salvage strategies for patients who relapse or who are refractory to treatment with purine analogues. In this review the different treatment options available are discussed and recommendations for the clinical management of the HCL are summarised.

Long-term outcome with pentostatin treatment in hairy cell leukemia patients. A French retrospective study of 238 patients

With the introduction of new drugs such as alpha-interferon (IFN) and purine analogs, the management of hairy cell leukemia (HCL) patients has changed. However, deoxycoformycin (DCF) produced higher complete remission rates than IFN. The current study was undertaken to provide long-term data on duration of overall survival (OS) and disease-free survival (DFS) and incidence of subsequent malignancies. We retrospectively analyzed the data of patients treated with DCF (4 mg/m2/day, every 2 weeks) from 39 French centers. In 84 of 238 included patients, DCF was the first-line therapy. Pretreatment variables influencing the achievement of complete remission, DFS, and OS were identified by multivariate analysis. Two hundred and thirty-eight patients received a median of nine cycles (range, 1-19 cycles). A complete remission was obtained in 182 of 230 evaluable patients (79%) and a partial response was obtained in 38 patients, for an overall response rate of 95.6%. In the multivariate analysis hemoglobin level less than 100 g/l and leukocytes less than 2 x 10(9)/l were parameters adversely influencing complete remission achievement. With a median follow-up of 63.5 months (range, 0.39-138.4 months), disease recurrence was observed in 34 of 220 responding patients (15%). The estimated 5-years and 10-years DFS was 88.1% and 68.8%, respectively. Hemoglobin level less than 100 g/l and leukocytes less than 2 x 10(9)/l were the pre-treatment variables associated with a shorter DFS. The estimated 5-year and 10-year OS were 89.4% and 88.7%, respectively. Hemoglobin level less than 100 g/l, leukocytes less than 2 x 10(9)/l, and adenopathy were significant factors of reduced survival. Hematologic toxicity was the main side-effect, followed by infection and emesis. During the period of follow-up, 18 patients developed second cancer, but the standardized incidence ratio was 0.95. Pentostatin is a highly effective regimen for hairy cell leukemia that produces durable complete responses. Toxicity of DCF is acceptable. Subsequent malignancies do not appear to be increased with pentostatin treatment.

The diagnosis and treatment of hairy-cell leukaemia

The diagnosis of HCL is usually straightforward and is based on the identification of typical HCs in the blood and bone marrow. The suspected diagnosis is confirmed by a combination of TRAP cytochemistry, a distinctive immunophenotype and characteristic BM trephine appearances. Nucleoside treatment is highly effective in inducing prolonged remissions; relapsing patients can usually be successfully retreated with nucleoside. Monoclonal antibody therapy is a promising novel approach to the treatment of resistant disease.

Simultaneous diagnosis of hairy cell leukemia and chronic lymphocytic leukemia/small lymphocytic lymphoma: a frequent association?

The association of hairy cell leukemia (HCL) with other neoplasms, mainly non-Hodgkin's lymphomas, is well known. However, the simultaneous diagnosis of HCL and chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is rare, with only few cases of such an association having been reported. We describe three patients with a well-characterized HCL in whom a CLL/SLL population was detected. Of note, these cases represent a significant proportion (11.5%; 95% CI: 0% to 24%) of the total number of HCL cases diagnosed in our institution during the same period of time. All three patients were treated with deoxycoformycin. They achieved a complete response of the HCL, whereas the CLL/SLL population persisted in all cases. The immunoglobulin gene rearrangement analysis, in two informative cases, suggested that the HCL and CLL/SLL populations arose from different B cell clones. This study indicates that the association of HCL and CLL/SLL might be much more frequent than previously recognized. Therefore, a large panel of monoclonal antibodies, including those necessary to detect CLL/SLL, should be employed when studying patients with HCL.

Risk of second cancer in patients with hairy cell leukemia: long-term follow-up

PURPOSE

The purpose of the present study was to assess the risk of second cancers in patients with hairy cell leukemia (HCL).

PATIENTS AND METHODS

We investigated the incidence of additional cancers in those patients registered in the nationwide registry of the Italian Cooperative Group for the Study of HCL, asking the cooperating centers for additional information on initial and subsequent therapies and on time and type of second malignancies, if they developed. Here we report the final results of this survey, consisting of 54 cases of second malignancies (excluding nine cases of epithelial skin cancer) which developed in 54 patients of 1,022 with adequate follow-up.

RESULTS

The cumulative risk of development of a second cancer was 5%, 10%, and 14% at 5, 10, and 15 years, respectively. The incidence of second malignancies was not significantly higher than the expected rate (standardized incidence ratio [SIR], 1.01; 95% confidence interval [CI], 0.74 to 1.33; P = 1.0). However, the SIR of non-Hodgkin's lymphoma in the entire cohort was 5.3 (95% CI, 1.9 to 11.5). Second malignancies occurred in eight (4.7%) of 386 patients who never received interferon (IFN), nine (5.9%) of 495 patients treated with IFN at the time of diagnosis, and seven (6.9%) of 102 patients who received IFN as second-line therapy. These differences were not statistically significant. Analysis of the separate calendar periods did not reveal any particular trends with respect to variations in SIR.

CONCLUSION

The present study does not support the suspicion that patients with HCL are at increased risk of additional second malignancies, although the incidence of lymphoid neoplasms was significantly higher than expected. In addition, our data indicate that IFN therapy did not exert an oncogenic effect in such patients.

A novel therapeutic strategy against monocytic leukemia with deoxyadenosine analogs and adenosine deaminase inhibitors

The adenosine deaminase inhibitor 2'-deoxycoformycin (dCF) significantly inhibits the proliferation of leukemia and lymphoma cells in the presence of either 2'-deoxyadenosine (dAdo) or its analog adenine arabinoside (araA). The concentration of dCF required to induce apoptosis of monocytoid leukemia cells is much lower than that required for myeloid, erythroid, or lymphoma cells. dATP effectively induces caspase-3 activation in cytosol from monocytoid cells, but not in that from non-monocytoid cells, suggesting that dATP-dependent caspase-3 activation is involved in the preferential induction of apoptosis in monocytoid leukemia cells. Athymic nude mice inoculated with human monocytoid leukemia U937 cells show significantly prolonged survival following combined treatment with dCF and araA. The clinical usefulness of the combination of adenosine deaminase inhibitor and dAdo analog is discussed.

Malignancy: Current Clinical Practice: Treatment of Hairy Cell Leukemia at the Close of the 20th Century

In the last half of this century, hairy cell leukemia was recognized as a distinct B-cell malignancy, accounting for 2% of all leukemias. Characteristics include splenomegaly, pancytopenia, a usually indolent course, and responsiveness to both interferon and purine analog therapy. Accurate diagnosis requires the demonstration of malignant cells in the bone marrow and peripheral blood which contain cytoplasmic projections and characteristic surface antigens. Splenectomy was identified early as a palliative therapy, and in 1984 systemic treatment with interferon alpha was first reported to induce complete remissions. Soon thereafter, the purine analog deoxycoformycin was found to induce more durable complete remissions in a higher percentage of patients. In 1990, 2-Chlorodeoxyadenosine, a new purine analog therapy, was reported to be capable of inducing long-term durable responses in most patients after a single cycle. Current challenges include identifying which purine analog is the least toxic since both appear similarly effective, and neither appear to add to the already increased rate of second malignancies occurring in these patients. Moreover, up to 25% of patients with hairy cell leukemia fail initially or eventually to respond to standard therapy, making the development of new approaches necessary. The characteristic bright expression of several B-cell antigens on the malignant cells, including CD20, CD22 and CD25, has led to the development of targeted biotherapeutic approaches. A recombinant immunotoxin targeting CD25 has recently been reported to induce major responses and it is likely that other successful targeted approaches will be reported early in the new century.

Hairy cell leukemia: treatment prospects

The recent advances in the management of hairy cell leukemia, a chronic and indolent B-cell lymphoproliferative disorder are reviewed. The introduction of alpha-interferon, purine analogs and recombinant monoclonal antibodies/immunotoxins has dramatically improved the outcome in a disease that once had a dismal prognosis. The underlying genetic defect remains unknown.

Deoxycoformycin in the treatment of patients with hairy cell leukemia: results of a Spanish collaborative study of 80 patients

BACKGROUND

Deoxycoformycin (DCF) has been reported to produce high response rates in patients with hairy cell leukemia (HCL), but to the authors' knowledge data regarding experience with such therapy in a large HCL series are scarce.

METHODS

Between 1988-1997, DCF (4 mg/m(2)/day, every 2 weeks) was administered to 80 HCL patients in 32 Spanish institutions. In 35 of 78 evaluable patients DCF was the first-line therapy; the remaining 43 patients had received other therapies. Pretreatment variables influencing the achievement of complete remission (CR) and event free survival were identified by multivariate analyses.

RESULTS

The median number of cycles administered was 7 (range, 1-22 cycles). A CR was obtained in 56 patients (72%) and a partial remission was obtained in 13 patients, for an overall response rate of 88%. In the multivariate analysis previous splenectomy and an Eastern Cooperative Oncology Group (ECOG) performance status > or = 2 were the parameters adversely influencing CR achievement. With a median follow-up of 31.2 months (range, 0.4-126.5 months), disease recurrence was observed in 11 of the CR patients, 5 of whom showed a further response to DCF. An ECOG performance status > or = 2 was the only pretreatment variable associated with a shorter event free survival. Seven patients died, four during the treatment period. The actuarial median event free survival was 46 months (95% confidence interval, 22.5-69.5 months), and 48.7% of the 56 patients who achieved a CR were expected to be alive and disease free at 5 years. Hematologic toxicity (marked neutropenia [22 cases], anemia [6 cases], and thrombocytopenia [1 case]) was the main side effect, followed by nausea and emesis (5 cases); 14 patients required hospitalization.

CONCLUSIONS

The results of the current study confirm the effectiveness and acceptable toxicity of DCF in the treatment of patients with HCL.