Therapeutic advances in the treatment of hairy cell leukemia

Disseminated Histoplasmosis with Concurrent Hairy Cell Leukemia

Histoplasmosis is an endemic fungal infection that can lead to disseminated disease, especially in immunosuppressed patients. Hairy cell leukemia is a rare, slow-growing hematological malignancy. Concurrence of histoplasmosis and hairy cell leukemia is extremely rare. We describe a 69-year-old male who presented with fever, dry cough, pancytopenia, multiple pulmonary nodules, and massive splenomegaly. Histoplasma urinary antigen was positive and disease was confirmed by biopsy of lung lesions. Peripheral smear showed 'hairy cells', and bone marrow biopsy revealed findings of hairy cell leukemia. The patient was treated with intravenous amphotericin, followed by oral itraconazole. After the initial treatment of infection, treatment for hairy cell leukemia was started with cladribine. We will discuss the principles of treating disseminated histoplasmosis in the setting of immunosuppression, and hairy cell leukemia with coexisting infection.

Modern strategies for hairy cell leukemia

Enormous progress in the treatment of hairy cell leukemia over the last five decades has emerged as a result of organized clinical investigations. Although interferon represented one of the initial major therapeutic advances in the management of this disease in 1984, the subsequent introduction of purine nucleoside analogs (pentostatin and cladribine) changed the natural history of this rare disease by achieving a high rate of complete and durable remissions. The disease-free survival after effective therapy has not reached a plateau, suggesting control but not cure of the disease. Identification of minimal residual disease in patients achieving a complete hematologic remission provides insight into the potential source for predicting eventual relapse. Modern strategies of targeted therapies directed against immunophenotypic markers on the leukemic cells provide hope that improved long-term control of the disease is possible. Combined chemoimmunotherapy may hold the highest promise for disease eradication, but the optimal strategy for using this approach is under active investigation. Despite the perception by hematologists that this disease has already been conquered, there are critically important unanswered questions that remain. Investigation of the bone marrow microenvironment and its impact on minimal residual disease may ultimately prevent relapse. Consideration of the median age of patients at diagnosis combined with a substantial relapse rate mandates continued pursuit of improved therapy. The ultimate goal will be to achieve cure rather than simple control of the disease.

CD52 expression in hairy cell leukemia

Hairy cell leukemia (HCL) is a rare chronic B-cell lymphoproliferative disorder characterized by splenomegaly, pancytopenia, and circulating atypical lymphocytes with circumferential cytoplasmic projections. Although uncommon, HCL cases refractory to standard therapy occur, and effective alternatives are limited. There is evolving literature supporting monoclonal antibody therapy in the treatment of B-cell lymphoid malignancies, including anti-CD52 (Campath-1H, alemtuzumab). We have examined nine cases of HCL and one case of HCL variant by flow cytometry for CD52 expression. All cases expressed CD52 antigen in 92-100% of the malignant cells. The demonstration of CD52 antigen expression on HCL cells provides the rationale for the use of alemtuzumab in refractory HCL.

Hairy cell leukemia: an update

Hairy cell leukemia is an indolent, chronic B-cell lymphoproliferative disorder comprising approximately 2 to 3% of all adult leukemias in the United States. Hairy cells are clonal expansions of mature, activated B-cells. They co-express CD11c, CD19, CD20, CD22, CD25, and CD103. Hairy cells possess clonal immunoglobulin gene rearrangements and express monoclonal surface immunoglobulin of either IgG or multiple heavy-chain isotypes. Treatment of hairy cell leukemia should be considered for symptomatic patients. It is indicated in patients with significant neutropenia, anemia, thrombocytopenia, symptomatic splenomegaly, constitutional symptoms due to hairy cell leukemia, or recurrent serious infections. Many treatments exist, including cladribine, pentostatin, interferon-alpha, splenectomy, rituximab (mabthera), and BL-22 immunotoxin.

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.

Pathology of hairy-cell leukaemia

Hairy-cell leukaemia (HCL) is a low grade B-cell lymphoproliferative process that presents either with lymphocytosis or neutropenia/monocytopenia. It is a disease predominantly of bone marrow and spleen, although it can also involve other organs and sites. Recent advances including multi-parameter flow cytometry and the development of antibodies with high specificity for HCL have permitted precise distinction of typical HCL from other lymphoproliferative diseases that can morphologically mimic the appearance of HCL. Although there is a commonly held belief that HCL is associated with a significant increase in second neoplasms, several recent studies have not supported this notion. The development of extremely effective therapy for HCL results in a high incidence of complete remission. However, a significant percentage of patients continue to harbour minimal residual disease that can be revealed with immunohistochemical and flow cytometric studies.

Cladribine in the treatment of hairy-cell leukaemia

Cladribine, a purine nucleoside analogue, is a safe and effective treatment for patients with hairy-cell leukaemia. It is administered at a dose of 0.09 mg/kg daily as a continuous intravenous infusion over 7 days. This chapter discusses the history, rationale, chemical structure and mechanism of action of cladribine. The indications for therapy and guidelines for clinical usage are reviewed. The response of hairy-cell leukaemia to cladribine, the acute and chronic complications and the risk for second malignancies are summarized. The chapter concludes with a section on salvage therapy.