Efficacy of Rituximab in Hairy Cell Leukemia.

BACKGROUND: Hairy Cell Leukemia (HCL) is a rare B-chronic lymphoproliferative disorder (BCLD) with an indolent course. First-line treatment modalities include 2-chlorodeoxyadenosine (2-CDA), 2-deoxycoformycin (2-DCF) and interferon-alpha. The efficacy of anti-CD20-Rituximab (R) in other BCLDs, as well as strong CD20 expression by HCL cells, indicate that R could be an alternative treatment of HCL.

AIMS: The experience of a single Hematology Unit in the treatment of relapsed HCL with R.

PATIENTS AND METHODS: We retrospectively analyzed all HCL patients (pts) who received R as salvage therapy in 1^st or subsequent relapse.

RESULTS: 13 patients treated with R were located among 110 patients diagnosed with HCL between 1980 and 2005. 11 were males and their median age before R treatment was 46 years (range: 42–88). 5 pts had splenomegaly with a median spleen size of 7cm below left costal margin (range:5–20cm). 3 pts has an absolute neutrophil count<1.5×10⁹/L, 4 a hemoglobin <10g/dL and 5pts a platelet count<100×10⁹/L. All patients displayed a typical immunophenotype from blood and/or bone marrow (CD20 strongly +, CD19+, CD22+, FMC-7+, CD11c+, CD25+, CD103+). Four of them were CD23+ and two CD10+. 8 pts received Rituximab at 1st relapse. Among them, one had received 2-DCF as first-line treatment, one 2-CDA and 6 interferon-alpha as induction and maintenance. 3 pts had received more than one prior treatments. Two pts received R at diagnosis, due to older age. The median time from diagnosis to R initiation was 61 months (range: 4–275). R was administered at 375mg/m² weekly for 6 cycles. Overall response rate was 67%, with 4 pts showing a negative immunophenotype. One pt discontinued treatment after the first cycle due to the development of thrombocytopenia that was attributed to the drug. 7/8 responders showed a complete restoration of their cytopenias. No other complications were recorded, except of mild infusion-related symptoms. Among the responding pts, none has relapsed so far with a median follow-up of 14 months (range: 4–40+). Among partial responders, one achieved a complete response including a negative bone marrow and immunophenotype after R retreatment.

CONCLUSIONS: R is a highly effective and tolerable treatment for HCL in relapse with a response rate of 67%. Retreatment or maintenance with R may be important, since ongoing responses are seen.