Hairy cell leukemia. Durability of response to splenectomy in 26 patients and treatment of relapse with androgens in six patients

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.

Novel therapeutic options for relapsed hairy cell leukemia

The majority of patients with hairy cell leukemia (HCL) achieve a response to therapy with cladribine or pentostatin with or without rituximab. However, late relapses can occur. Treatment of relapsed HCL can be difficult due to a poor tolerance to chemotherapy, increased risk of infections and decreased responsiveness to chemotherapy. The identification of BRAFV600E mutations and the role of aberrant MEK kinase and Bruton's tyrosine kinase (BTK) pathways in the pathogenesis of HCL have helped to develop novel targeted therapies for these patients. Currently, the most promising therapeutic strategies for relapsed or refractory HCL include recombinant immunoconjugates targeting CD22 (e.g. moxetumomab pasudotox), BRAF inhibitors such as vemurafenib and B cell receptor signaling kinase inhibitors such as ibrutinib. Furthermore, the VH4-34 molecular variant of classic HCL has been identified to be less responsive to chemotherapy. Herein, we review the results of the ongoing clinical trials and potential future therapies for relapsed/refractory HCL.

Update on the biology and treatment options for hairy cell leukemia

Hairy cell leukemia (HCL) is an uncommon chronic leukemia of mature B cells. Leukemic B cells of HCL exhibit a characteristic morphology and immunophenotype and coexpress multiple clonally related immunoglobulin isotypes. Precise diagnosis and detailed workup is essential, because the clinical profile of HCL can closely mimic that of other chronic B-cell lymphoproliferative disorders that are treated differently. Variants of HCL, such as HCLv and VH4-34 molecular variant, vary in the immunophenotype and specific VH gene usage, and have been more resistant to available treatments. On the contrary, classic HCL is a highly curable disease. Most patients show an excellent long-term response to treatment with single-agent cladribine or pentostatin, with or without the addition of an anti-CD20 monoclonal antibody such as rituximab. However, approximately 30-40 % of patients with HCL relapse after therapy; this can be treated with the same purine analogue that was used for the initial treatment. Advanced molecular techniques have identified distinct molecular aberrations in the Raf/MEK-ERK pathway and BRAF (V600E) mutations that drive the proliferation and survival of HCL B cells. Currently, research in the field of HCL is focused on identifying novel therapeutic targets and potential agents that are safe and can universally cure the disease. Ongoing and planned clinical trials are assessing various treatment strategies, such as the combination of purine analogues and various anti-CD20 monoclonal antibodies, recombinant immunotoxins targeting CD22 (e.g., moxetumomab pasudotox), BRAF inhibitors, such as vemurafenib, and B-cell receptor signaling inhibitors, such as ibrutinib, which is a Bruton's tyrosine kinase inhibitor. This article provides an update of our current understanding of the pathophysiology of HCL and the treatment options available for patients with classic HCL. Discussion of variant forms of HCL is beyond the scope of this manuscript.

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.

Historical aspects and milestones in the development of effective treatment for hairy cell leukemia

Hairy cell leukemia (HCL) is a rare B-cell lymphoproliferative disorder, but is gratifying to treat for both physicians and patients. During the 50 years since its initial description as a clinical entity, hematologists have been fascinated by the bizarre appearance of the malignant cell with its hair-like projections. Therapeutic strategies have evolved from splenectomy to interfere to the purine analogues which have become the treatments of-choice and are very effective. Immunoconjugate Therapy with BL22 (anti-CD22 [corrected] antibody linked to truncated to Pseudomonas exotoxin) represents the newest milestone in the development of effective treatment for hairy cell leukemia.

Splenectomy, Interferon, and Treatments of Historical Interest in Hairy Cell Leukemia

The evolution and "lessons learned" for therapeutic options and approaches in HCL, which subsequently evolved into the adenosine deaminase inhibitors as the treatment of choice, has been intriguing. The contributions to patient care and individual patient lives have been remarkable. Observation, splenectomy, and recombinant interferon are potential therapeutic are alternatives in select patients as initial therapy, and as therapeutic alternatives in the 10% of patients who have progressive disease after the purine nucleoside analogs.

Splenectomy and treatments of historical interest

Hairy-cell leukaemia (HCL) was initially described as a distinct clinical entity in 1958. Various types of therapy have been evaluated since this initial description and several are currently important only for historical comparison. Hairy-cell leukaemia serves as an example of rapid progress in the development of effective therapeutic strategies. Splenectomy was the first effective treatment because it resulted in an improvement in cytopenias and relief from symptomatic splenomegaly. However, complete remission of the disease was observed only very rarely. Splenectomy was considered an appropriate initial therapy from the 1950s to the early 1980s, although no randomized controlled studies have ever shown improved survival with this approach. In the early 1980s, more effective treatments were identified, initially interferon-alpha, then the purine analogues 2-deoxycoformycin and 2-chlorodeoxyadenosine (2-CdA). These types of therapy have been so effective that most previous treatments are now obsolete. Although the purine analogues result in sustained remissions in the majority of patients, a relatively small percentage of patients relapse and require other types of therapy. Splenectomy may be necessary in some instances. In this chapter the role of splenectomy is reviewed and other types of therapy of historical interest are presented.

Serum dehydroepiandrosterone and DHEA-sulfate in patients with adult T-cell leukemia and human T-lymphotropic virus type I carriers

The serum levels of dehydroepiandrosterone (DHEA) and DHEA-sulfate (DHEA-S) were determined by radioimmunoassay in 38 patients with adult T-cell leukemia (ATL). Levels of serum DHEA and DHEA-S were also measured in 60 human T-lymphotropic virus type I (HTLV-I) carriers, and did not differ from those in 60 healthy control subjects. Serum levels in patients with ATL were lower than those in the age- and sex-matched healthy controls and in HTLV-I carriers with statistical significance. Serum DHEA and DHEA-S in male patients with acute and lymphoma-type ATL were 1.06 +/- 0.77 ng/ml and 245.8 +/- 192.9 ng/ml, respectively. Levels in male patients with chronic and smoldering-type ATL were 1.69 +/- 0.68 ng/ml and 477.6 +/- 251.5 ng/ml, respectively. Serum levels of DHEA and DHEA-S in patients with acute and lymphoma-type ATL were significantly lower than those in patients with chronic and smoldering-type ATL (P < 0.05). These data suggest that a decrease in serum levels of DHEA and DHEA-S may be associated with patients who have some clinical subtypes of ATL. Moreover, androgens may have a therapeutic role in patients with ATL, as administered in patients with hairy-cell leukemia. Because there is at present no curative chemotherapy for ATL, a trial combination of androgens and standard chemotherapy may be a reasonable therapeutic option in such patients.

Advances in therapy for hairy cell leukemia. A review

BACKGROUND

Hairy cell leukemia (HCL) is a chronic B-cell malignancy, typically seen in middle-aged men, characterized by pancytopenia, splenomegaly, immunologic abnormalities, and morphologically typical neoplastic mononuclear cells in the blood, bone marrow, liver, spleen, and other tissues. Diagnosis is confirmed by demonstration of hairy cells in biopsy specimens from the bone marrow or spleen or in peripheral blood. The natural history of this lymphoproliferative disorder varies. Patients may die early during the initial phase of therapy; others may require no therapy; and for some, splenectomy alone, without further treatment, may suffice for many years. Recently, the nucleosides pentostatin (2'-deoxycoformycin) (DCF) and 2'-chlorodeoxyadenosine (2-CdA) have been shown to produce greater numbers of durable complete remissions with curative potential in patients with HCL. The treatment options, with emphasis on major therapeutic advances with alpha-interferon, DCF, and 2-CdA, are reviewed in this article.

METHODS

Studies on HCL published from 1958 to 1992 were reviewed using the Cancerline and Medline retrieval systems and other bibliographies.

RESULTS

Management of HCL has changed in the last decade as a result of three new effective agents: alpha-interferon DCF, and 2-CdA. DCF has produced an overall response rate of 86% and a complete remission rate of 62%. 2-CdA has yielded an overall response rate of 95% and a complete remission rate of 82%. Alpha-interferon has given an overall response rate of 82% and a complete remission rate of 8%. Other agents with limited activities include chlorambucil, cyclophosphamide, cytarabine, vincristine, doxorubicin, and zorubicin hydrochloride. The effects of lithium carbonate, immunotherapy, splenic irradiation, androgens, and leukaphoresis are minimal and transient.

CONCLUSIONS

Modern management of HCL with 2-CdA and DCF is now potentially curative rather than palliative in some patients; however, the optimal therapeutic approach remains uncertain. Alpha-interferon has been approved by the Food and Drug Administration as the first-line drug therapy, followed by DCF in non-responding patients. 2-CdA remains an experimental therapy, but its higher response rate and ease of administration may make it the first-line treatment of choice. Additional research into the biology of HCL and further clinical trials are needed to determine the optimal treatment strategy for this disorder. Therefore, the best therapeutic approach at the current time is to include patients with HCL in ongoing clinical trials.

Splenectomy in lymphoproliferative disorders: a report on 70 cases and review of the literature

Between February, 1970 and September, 1991, we performed splenectomies on 70 patients with chronic lymphoproliferative disorders including primary leukemias: 19 B-cell chronic lymphocytic leukemia, 1 B-cell prolymphocytic leukemia, 22 hairy cell leukemias, 4 large granular lymphocytic leukemias, 1 T-cell prolymphocytic leukemia, and non-Hodgkin's lymphomas (NHL): 10 splenic lymphomas with villous lymphocytes, 4 follicular lymphomas, 5 mantle cell lymphomas, 3 lymphoplasmacytic and 1 large cell NHL. The primary indications for surgery in this series were therapy-resistant disease (40%) and therapeutic splenectomy (38%). Postsplenectomy, 70% of patients had a complete hematological response, 23% had a partial response, and 7% were nonresponsive. Median treatment-free survival correlated with the hematologic response postsplenectomy and the underlying diagnosis. Better treatment-free survivals were seen in patients with lesser degrees of anemia and thrombocytopenia. Overall, improvements were more pronounced in the B-cell than in the T-cell disorders. Indications for further therapy, postoperative morbidity and mortality, and survival times are discussed along with a review of the literature. These findings advocate a continuing role for splenectomy in symptomatic lymphoid malignancies running with splenomegaly and hypersplenism.

Hairy cell leukemia: clinical features and therapeutic advances

Hairy cell leukemia (HCL) is a rare chronic lymphoproliferative disorder which has been extensively studied over the past decade. Much has been learned regarding the diagnosis, natural history, biology, and treatment of this unique neoplasm. The disease most commonly affects middle aged men and characteristic clinical features include splenomegaly, cytopenias, and usually the presence in the peripheral blood of distinctive 'hairy cells' with irregular cytoplasmic projections. Diagnosis can usually be confirmed by bone marrow biopsy. Although the natural history can be extremely variable among patients, complications are usually referable to the cytopenias, with anemia and infection being most frequent. In addition to pyogenic infections, patients are susceptible to unusual organisms including atypical mycobacterium, legionella, and fungi. The requirement of red blood cell transfusion, severe granulocytopenia or thrombocytopenia, frequent infections, or painful splenomegaly are all indications for treatment. Splenectomy is the standard initial treatment of choice. However, in the past few years there have been exciting major advances in the therapeutic modalities for HCL. Recombinant alpha-interferon is highly effective, with beneficial responses occurring in close to 90% of patients. The Food and Drug Administration has recently approved the use of interferon for HCL. This represents the first time a biological response modifier has been approved for the treatment of human disease. In addition, preliminary results with the adenosine deaminase inhibitor, 2'deoxycoformycin (dcf), have been encouraging. Further clinical trials are required in order to determine the optimal sequential treatment strategy for HCL. The exact mechanisms of action of both interferon and dcf in HCL remain to be elucidated. A better understanding of the unusual features of the hairy cell and the underlying biological effect of these two agents in HCL may have important applications in other hematologic and non-hematologic malignancies.