Phase 2 study of cladribine followed by rituximab in patients with hairy cell leukemia.

We conducted this study to determine the feasibility and safety of cladribine followed by rituximab in patients with hairy cell leukemia including the vari-ant form (HCLv). Cladribine 5.6 mg/m² given IV over 2 hours daily for 5 days was followed ∼ 1 month later with rituximab 375 mg/m² IV weekly for 8 weeks. Responses were recorded and BM minimal residual disease (MRD) was evaluated after the completion of rituximab. Thirty-six patients have been treated including 5 with HCLv. Median age was 57 years (range, 37-89). All patients (100%) have achieved complete response (CR), defined as presence of no hairy cells in BM and blood with normalization of counts (absolute neutrophil count [ANC]> 1.5 × 10⁹/L, hemoglobin [Hgb] > 12.0 g/dL, platelets [PLT] > 100 × 10⁹/L), as well as resolution of splenomegaly. There were no grade 3 or 4 nonhematologic adverse events directly related to the treatment. Only 1 patient (with HCLv) has relapsed; median CR duration has not been reached (range,1+-63+ months). Three patients with HCLv died including 1 with relapsed disease and 2 from unrelated malignancies. Median survival duration has not been reached (range, 2+-64+ months). Treatment with cladribine followed by rituximab is effective tk;4and may increase CR rate. This study was registered at www.clinicaltrials.gov as NCT00412594.