Treatment Option Overview

The initial therapies of choice are either cladribine (2-chlorodeoxyadenosine, 2-CdA) or pentostatin.[1] These drugs have comparable response rates but have not been compared in phase III trials. Cladribine is administered as a one-time continuous infusion or series of subcutaneous injections and is associated with a high rate of febrile neutropenia.[2,3,4,5] Rarely, more than one course of treatment is required to induce a desirable response. Treatment should be discontinued once complete remission or stable partial remission with normalization of peripheral blood counts is reached. The presence of residual disease may be predictive of relapse but does not seem to affect survival.[4,6]

The role of consolidation or maintenance therapy in preventing relapse or progression of the disease following treatment with purine analogs has not been evaluated and remains unproven. Pentostatin is administered intermittently for a longer treatment duration but may result in a lower incidence of febrile complications.[7,8] While most patients remain disease free 10 years after treatment with these purine analogs, no patient has been followed long enough to assess cure.[9,10] Both nucleoside analogs cause profound suppression of CD4 counts, which may last for a year, and a potential increased risk of second malignancies has been reported.[4,11]

A study of 3,104 survivors of hairy cell leukemia from the SEER database showed an increased risk of second cancers (standardized incidence ratio = 1.24; 95% CI, 1.11–1.37), especially for Hodgkin and non-Hodgkin lymphomas.[12] The increased risk for second cancers was seen even in the 2 decades prior to the introduction of purine nucleosides.[12] With the use of cladribine, an increased risk of second malignancies is possible among patients with hairy cell leukemia (observed to expected ratio of about 1.8 in several series after 6 years).[4,11] Several series using pentostatin did not report an increased risk of second malignancies.[7,9,13] For a few patients, such as those with severe thrombocytopenia, splenectomy might be considered.[14] After splenectomy, 50% of patients will require no additional therapy, and long-term survivors are common. Therapy with interferon-alpha is another treatment option, especially for patients with intercurrent infection.[8,15]

Hairy cell leukemia variant has a distinctive phenotype and typically presents with leukocytosis instead of leukopenia.[16] These patients have poorer responses to initial cladribine, shorter durations of response, and typically do not respond again to purine analogues after relapse. Combinations of rituximab and purine analogues are under evaluation and further studies are required to define optimal therapies.[17,18]

References:

1. Gidron A, Tallman MS: 2-CdA in the treatment of hairy cell leukemia: a review of long-term follow-up. Leuk Lymphoma 47 (11): 2301-7, 2006.
2. Hoffman MA, Janson D, Rose E, et al.: Treatment of hairy-cell leukemia with cladribine: response, toxicity, and long-term follow-up. J Clin Oncol 15 (3): 1138-42, 1997.
3. Cheson BD, Sorensen JM, Vena DA, et al.: Treatment of hairy cell leukemia with 2-chlorodeoxyadenosine via the Group C protocol mechanism of the National Cancer Institute: a report of 979 patients. J Clin Oncol 16 (9): 3007-15, 1998.
4. Goodman GR, Burian C, Koziol JA, et al.: Extended follow-up of patients with hairy cell leukemia after treatment with cladribine. J Clin Oncol 21 (5): 891-6, 2003.
5. Jehn U, Bartl R, Dietzfelbinger H, et al.: An update: 12-year follow-up of patients with hairy cell leukemia following treatment with 2-chlorodeoxyadenosine. Leukemia 18 (9): 1476-81, 2004.
6. Fayad L, Kurzrock R, Keating M, et al.: Treatment of hairy-cell leukemia (HCL) with 2-CdA: long term follow-up at M.D. Anderson Cancer Center. Blood 90(suppl 1): A2363, 1997.
7. Ribeiro P, Bouaffia F, Peaud PY, et al.: Long term outcome of patients with hairy cell leukemia treated with pentostatin. Cancer 85 (1): 65-71, 1999.
8. Grever M, Kopecky K, Foucar MK, et al.: Randomized comparison of pentostatin versus interferon alfa-2a in previously untreated patients with hairy cell leukemia: an intergroup study. J Clin Oncol 13 (4): 974-82, 1995.
9. Flinn IW, Kopecky KJ, Foucar MK, et al.: Long-term follow-up of remission duration, mortality, and second malignancies in hairy cell leukemia patients treated with pentostatin. Blood 96 (9): 2981-6, 2000.
10. Chadha P, Rademaker AW, Mendiratta P, et al.: Treatment of hairy cell leukemia with 2-chlorodeoxyadenosine (2-CdA): long-term follow-up of the Northwestern University experience. Blood 106 (1): 241-6, 2005.
11. Au WY, Klasa RJ, Gallagher R, et al.: Second malignancies in patients with hairy cell leukemia in british columbia: a 20-year experience. Blood 92 (4): 1160-4, 1998.
12. Hisada M, Chen BE, Jaffe ES, et al.: Second cancer incidence and cause-specific mortality among 3104 patients with hairy cell leukemia: a population-based study. J Natl Cancer Inst 99 (3): 215-22, 2007.
13. Kurzrock R, Strom SS, Estey E, et al.: Second cancer risk in hairy cell leukemia: analysis of 350 patients. J Clin Oncol 15 (5): 1803-10, 1997.
14. Golomb HM, Vardiman JW: Response to splenectomy in 65 patients with hairy cell leukemia: an evaluation of spleen weight and bone marrow involvement. Blood 61 (2): 349-52, 1983.
15. Capnist G, Federico M, Chisesi T, et al.: Long term results of interferon treatment in hairy cell leukemia. Italian Cooperative Group of Hairy Cell Leukemia (ICGHCL). Leuk Lymphoma 14 (5-6): 457-64, 1994.
16. Matutes E, Wotherspoon A, Catovsky D: The variant form of hairy-cell leukaemia. Best Pract Res Clin Haematol 16 (1): 41-56, 2003.
17. Else M, Osuji N, Forconi F, et al.: The role of rituximab in combination with pentostatin or cladribine for the treatment of recurrent/refractory hairy cell leukemia. Cancer 110 (10): 2240-7, 2007.
18. Arons E, Suntum T, Stetler-Stevenson M, et al.: VH4-34+ hairy cell leukemia, a new variant with poor prognosis despite standard therapy. Blood 114 (21): 4687-95, 2009.