P14.02 Proton radiation therapy combined with immunomodulatory drugs for central nervous system invasive multiple myeloma: case report and review of the literature

Abstract Central nervous system invasion of multiple myeloma is a rare extra-medullary form of the disease, presenting as intraparenchymal lesions, leptomeningeal disease, or via direct dural invasion. Survival of leptomeningeal myelomatosis in historical series is considered to be extremely poor, but seems to be improving in the era of novel therapy, namely proteosome inhibitors and immunomodulatory class drugs. Here we present the case of a 48 year-old male with isolated central nervous system relapse of multiple myeloma who had multiple rapidly progressive intraparenchymal myeloma lesions, cauda equina lesions, as well as leptomeningeal myelomatosis that developed years after complete response to autologous stem cell transplant. This patient’s central nervous system disease progressed following systemic high-dose methotrexate, but demonstrated a durable partial response to proton beam craniospinal irradiation combined with immunomodulatory chemotherapy using pomalidomide plus dexamethasone. Little is known about the use of proton radiation therapy in the treatment of plasma cell neoplasms as compared to other hematologic malignancies (such as leukemia), nor about its efficacy, with no published reports to our knowledge. Finally, we review the current literature regarding treatment of both intraparenchymal and leptomeningeal myelomatosis.