Incidence, description, and timing of serious and opportunistic infections in patients with hairy cell leukemia.

Hairy cell leukemia is an uncommon B-cell malignancy with excellent response to purine analogs and to targeted therapies such as ibrutinib and vemurafenib. However, purine analogs are known to be highly immunosuppressive and the infection burden in this patient population with current therapies is unknown. We therefore conducted a retrospective cohort study following 149 patients. Median follow-up time was 6.9 years. Thirty-six percent developed an opportunistic or serious infection requiring hospitalization. Most cases were bacterial and most coincided with neutropenia and/or CD4 T-lymphopenia. No single treatment agent was significantly associated with increased or decreased incidence of infection. Reassuringly, the cumulative incidence of infections plateaued 2 months after initial treatment suggesting clinically significant immune recovery. Only one patient in our cohort passed away due to infection. Estimated 10-year overall survival was 99% suggesting that infections may not cause as much mortality as was seen prior to current therapies.