Maintenance Low-Dose BRAF Inhibition and Rituximab in Relapsed Hairy Cell Leukemia: A Therapeutic Alternative.

Hairy cell leukemia (HCL) is a rare, indolent B-cell neoplasm accounting for less than 2% of all leukemias. It is characterized by the presence of mature lymphocytes with typical hairy projections within the peripheral blood, bone marrow, and spleen, resulting in pancytopenia and splenomegaly. Purine analogs such as cladribine and pentostatin have been the mainstay of treatment for HCL. Despite high responsiveness to first-line therapy with purine analogs, almost half of the patients with HCL relapse and become progressively resistant to these medications. Treatment with a combination of BRAF V600E inhibitor and anti-CD20 monoclonal antibody has achieved durable responses in relapsed HCL. Here, we present a patient with relapsed and refractory HCL who achieved only partial response with three months of treatment with high-dose vemurafenib and rituximab, following which he was maintained on low-dose vemurafenib plus monthly rituximab for almost a year, after which he achieved complete morphologic and molecular response.