Central nervous system multiple myeloma: A real-world multi-institutional study of the Greek Myeloma Study Group.

Central nervous system (CNS) involvement is a rare and aggressive complication of multiple myeloma (MM). We identified 54/4352 MM patients (1.2%), who developed CNS-MM between 2000 and 2022. A matched-control group of MM patients without CNS-MM was used for comparisons. Median age was 63 years. Median time to CNS-MM was 28 months; 6/54 experienced CNS-MM at MM diagnosis. Abnormal lactate dehydrogenase (LDH), high-risk cytogenetics, and extramedullary involvement (EMI), that is, soft tissue plasmacytomas and/or plasma cell leukemia (PCL), were more frequent in CNS-MM versus controls (p < .05); 13/54 had PCL at CNS-MM. The majority had leptomeningeal infiltration (LMI) (66%); 26% had CNS-MM without systemic myeloma; EMI was the strongest predictor for CNS-MM (OR: 6.3). Median overall survival (OS) of CNS-MM patients versus controls was 43 months (95% CI: 32-54) versus 60 months (95% CI: 38-82) (p < .001); treatment of CNS-MM included mainly bortezomib/thalidomide/chemotherapy whereas 20% received novel drugs/immunotherapy combinations; 28 patients underwent cerebrospinal fluid infusions; EMI was the strongest negative predictor for post CNS-MM OS (p = .005; HR: 2.9). Treatment after 2016 predicted significantly for OS (p = .002; HR: 0.27). Median post CNS-MM OS was 4 months (95% CI: 2.6-5.4); in patients treated after 2016 median OS was 12 months. In conclusion, we have demonstrated in this large real-world series that survival of CNS-MM remains poor; however, there is a positive impact of treatment after 2016, related to the efficacy of modern anti-myeloma therapy; EMI significantly increases the probability to develop CNS-MM and the risk of post CNS-MM death, indicating a potential need for CNS prophylaxis for those patients.