A nationwide survey on central nervous system multiple myeloma in Japan: analysis of prognostic and treatment factors that impact survival.

This nationwide multicentre retrospective study was performed to analyze clinical features that predict the prognosis of central nervous system invasion in multiple myeloma (CNS-MM, approximately 1% of MM). Overall, of the 77 adult patients with CNS-MM identified between 2005 and 2016, those diagnosed at MM diagnosis (n = 3) had longer overall survival (OS) than those diagnosed at relapse (n = 74; median: 48·5 vs 2·7 months). Therefore, we compared the relapsed MM with CNS-MM in patients with any treatment (n = 60). Multivariate analyses revealed that lenalidomide treatment [hazard ratio (HR) 0·27, P = 0·003], intrathecal chemotherapy (IT; HR 0·54, P = 0·05), and radiation therapy (RTx; HR 0·33, P < 0·001) for CNS-MM had a positive effect on longer OS. These factors were used to develop a scoring system combining the number of treatments with lenalidomide, IT, and RTx (0, 1, 2, 3). The OS of CNS-MM patients was stratified based on these factors, with a median OS of 1·1, 4·5, and 7·5 months for patients with zero, one, two to three favourable features, respectively (0 vs 1, P = 0·0002; 1 vs 2-3, P = 0·08). Multimodal treatment including lenalidomide in addition to conventional IT and RTx can improve OS.