INTRODUCTION: Limited data exist with respect to the outcome and optimal treatment of patients with myelomatous involvement of the central nervous system (CNS). MATERIALS AND METHODS: Of 4060 patients with multiple myeloma (MM), evaluated at Mayo Clinic from 1998 to 2014, 29 (0.7%) had identifiable CNS involvement, established by the presence of atypical plasma cells in the cerebrospinal fluid (CSF) and/or identification of intraparenchymal or meningeal involvement on magnetic resonance imaging (MRI). A cohort of 87 MM patients without CNS disease served as the control group (1:3), matched by diagnosis date and gender. RESULTS: Plasma cells were detected in the CSF in 87% and MRI findings consistent with CNS involvement were noted in 82% of the patients. A bone marrow plasma cell labeling index of ≥ 3%, the presence of disease at other extramedullary sites, or peripheral blood plasma cells of > 800 per 150,000 events were associated with an odds ratio of 7.1, 10.3, and 14, respectively, for the risk of CNS involvement. Overall survival (OS) from the diagnosis of MM was significantly shorter in the CNS-MM group (median 40 months; 95% confidence interval [CI], 24-56 months) than in the control group (median, 93 months; 95% CI, 67-129 months). OS was 3.4 months from the detection of CNS disease. Patients who underwent autologous stem cell transplantation after CNS involvement (n = 7) had a median OS of 19 months (95% CI, 10-67 months) from the detection of CNS involvement. CONCLUSION: Myelomatous involvement of the CNS is a rare complication that portends a poor survival. Current therapeutic approaches appear to be largely ineffective for this subset of patients with MM.

4th Department of Internal Medicine Hematology Faculty of Medicine University Hospital Hradec Kralove Charles University Prague Hradec Kralove Czech Republic

Division of Hematology Mayo Clinic Rochester MN

Division of Hematology Ottawa Hospital University of Ottawa Ottawa ON Canada

Division of Neurology Mayo Clinic Rochester MN