Single-agent rituximab is an effective salvage therapy in pretreated hairy cell leukemia patients.

Single-agent rituximab can be a suitable treatment in hairy cell leukemia (HCL) patients relapsing after repeated courses of purine analogs, if purine analogs are contraindicated (e.g. in case of poor marrow cellularity, high disease infiltration predicting long-lasting aplasia) and if newer agents (moxetumomab or vemurafenib) are not easily available. Our institutional series of patients receiving single-agent rituximab as salvage therapy was 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. Thirty-three patients received 39 courses of rituximab (4 patients received it twice, one patient three times), as a median third line of therapy (range 2-8). 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%. In 28.2% of patients, we observed no response. Median TTNT was 33 months (65% at 2 years), median PFS was 24 months (51% at 2 years) and median OS resulted of 154 months (22% at 20 years). To our knowledge, this is the widest series of HCL patients receiving single-agent rituximab for disease relapse. Rituximab is an effective salvage therapy in pretreated HCL patients after failure of purine analogs. It may be repeated if no alternatives are available.