INNV-40. DURABLE 10-YEAR RESPONSE TO VEMURAFENIB IN A PATIENT WITH CNS HAIRY CELL LEUKEMIA

Abstract

Abstract Hairy cell leukemia (HCL) is an uncommon form of chronic B-cell lymphoproliferative disease, accounting for approximately 2% of all cases of leukemias. Although there have been rare instances of HCL affecting the central nervous system (CNS), these cases usually involve highly fatal leptomeningeal disease or direct leukemic infiltration into the brain. The BRAF V600E mutation, leading to the constitutive activation of the MAPK/ERK signaling pathway, is recognized as a key activating mutation in HCL and is present in almost all HCL patients. First-line treatment for HCL remains purine analogs; however, up to 20% of patients only achieve a partial response. Vemurafenib, an oral inhibitor of BRAF V600E, has demonstrated strong anti-tumor activity in patients with systemic relapsed/refractory HCL and has good CNS penetration. In this case study, we present a 67-year-old patient with HCL who initially presented with multifocal cranial neuropathies In August of 2013. His brain MRIs demonstrated multiple enhancing leptomeningeal foci. While a combination of cytarabine, methotrexate, and rituximab initially prevented disease progression, he experienced multiple relapses over the course of 2 years and eventually became refractory to treatment. Subsequently, the patient was started on vemurafenib, which resulted in the complete resolution of all lesions observed on MRIs. This response has persisted for 10 years since starting the medication. We suggest that besides its high response rate in systemic relapsed/refractory HCL, vemurafenib may offer benefits for patients with CNS involvement who are refractory to conventional chemotherapies and can achieve a durable response. Further investigation is needed to potentially establish vemurafenib as a first-line treatment option for HCL patients with CNS involvement.