Single‐agent rituximab as an effective salvage therapy in pre‐treated hairy cell leukemia

Introduction: Hairy cell leukemia (HCL) patients usually experience multiple disease relapses during the course of their disease. The CD20 antigen is highly expressed on the surface of hairy cells. Single-agent rituximab can be a suitable treatment options in patients relapsing after repeated courses of purine analogs, if purine analogs are contraindicated (e.g., in case of poor bone marrow cellularity, high disease infiltration predicting long-lasting aplasia), especially if newer agents (such as moxetumomab or vemurafenib) are not easily available (as it happens in several countries). Methods: Our institutional series of HCL patients receiving single-agent rituximab as salvage therapy was retrospectively reviewed. Patients received rituximab at the standard dose of 375 mg/m2 weekly for 4 weeks. The main study objectives were overall response rate (ORR), time-to-next treatment (TTNT), progression-free survival (PFS) and overall survival (OS). Responses have been categorized according to the Consensus Resolution Criteria. Results: Thirty-three patients received 39 courses of rituximab (4 patients received it twice, one patient three times), in median as third line of therapy (range 2–8). First rituximab was given at a median age of 61 years and at a median time from disease diagnosis of 65 months. Out of 39 courses, a complete response was obtained in 28.2% of cases, a partial response in 23.1% and a minimal response in 20.5%, yielding an ORR of 71.8%. In 28.2% of patients, we observed no response. Median TTNT was reached at 33 months (65% at 2 years), while median PFS was reached at 24 months (51% at 2 years). Median OS resulted of 154 months (22% at 20 years). Among the 5 patients receiving rituximab more than once, all responded after the first course, although the ORR after the second or later course was only 50%. Median TTNT following the first rituximab was 38.5 months in these patients, ranging from 15 to 205 months. Keywords: Immunotherapy, Lymphoid Cancers No conflicts of interests pertinent to the abstract.