Treatment outcomes with purine nucleoside analog alone or with rituximab for hairy cell leukemia at first relapse

Introduction: Frontline treatment of hairy cell leukemia (HCL) with a single course of the purine nucleoside analog (PNA) produces a high rate of complete remission (CR) with prolonged durations. At the time of relapse, although treatment guidelines recommend re-treatment with a PNA alone or in combination with rituximab (R), practice patterns vary and data supporting each approach are limited. Methods: We conducted a multisite outcomes analysis of patients treated for HCL between 1995 and 2018 at six US medical centers. All patients were treated with frontline PNA and subsequently required treatment with a PNA alone (PNA) or with R (+R). Results: Of the 88 patients analyzed, 56 (63.6%) received second-line PNA and 22 (36.4%) received a PNA + R. Baseline characteristics of both groups were similar. There was no difference in median PFS [67 months (95% CI 43.8 non-reached (NR)) vs. 65 months (95% CI 60-NR)] or 5-year OS [98% (95% CI 0.94–1) vs. 94% (95% CI 0.83–1), p =.104] in the PNA versus PNA + R cohorts, respectively. Conclusion: To our knowledge, this is the largest study evaluating the role of R in treatment of relapsed HCL and suggests that there is no advantage to the addition of R to PNA therapy at the time of first re-treatment.