[Multiple myeloma with central nervous system involvement successfully treated with a multimodal therapy including elranatamab]

Central nervous system involvement in multiple myeloma (CNS-MM) is rare and associated with a poor prognosis. We report a case of multidrug-refractory CNS relapse that responded to a multidisciplinary treatment approach including elranatamab. The patient was a 75-year-old man who was refractory to anti-CD38 antibodies, IMiDs, proteasome inhibitors, anti-SLAMF7 antibodies, and alkylating agents. He developed progressive somnolence, and his Japan Coma Scale (JCS) score deteriorated to 20. Cerebrospinal fluid (CSF) cytology revealed class IV plasma cells, leading to a diagnosis of CNS-MM. After initiation of intrathecal methotrexate, cytarabine, and prednisolone, combined with anti-CD38 antibody and elranatamab, neurological status improved (JCS score: 1). CSF cytology improved from class IV to class III and ultimately to class II, with disappearance of plasma cells. Grade ≥3 adverse events were neutropenia, anemia, and thrombocytopenia. This case suggests that a multidisciplinary treatment approach incorporating elranatamab may represent a promising therapeutic option for patients with multidrug-refractory CNS-MM.