Abstract:  Objective To investigate the efficacy and safety of daratumumab combined with bendamustine in patients with relapsed/refractory multiple myeloma complicated by secondary extramedullary disease. Methods The clinical data of  patients with relapsed/refractory multiple myeloma complicated by secondary extramedullary disease hospitalized in Guangxi Medical University Cancer Hospital from January 2021 to December 2023 were analyzed retrospectively. All patients had progressive disease on at least 3 prior treatment lines and followed by combination therapy with daratumumab and bendamustine. The efficacy and safety of the treatment were assessed based on the International Myeloma Working Group (IMWG) criteria and the National Cancer Institute⁃Common Terminology Criteria for Adverse Events (NCI⁃CTCAE) version 5.0. Results A total of 12 patients were included in the analysis, with 2 achieving complete response, 4 achieving partial response, 2 achieving minimal response, 1 achieving stable disease, and 3 experiencing  progressive disease. The overall response rate was 50%, and the median progression⁃free survival was 8 months. All patients experienced hematological toxicity, 4 of which were grade Ⅲ-Ⅳ. Additionally, 3 patients developed pneumonia during treatment, no treatment⁃related deaths occurred. Conclusions The combination of daratumumab and bendamustine demonstrates effectiveness in treating relapsed/refractory multiple myeloma complicated by secondary extramedullary disease, with manageable toxicities. This result deserves further investigation with a larger patient population.

Key words: Multiple myeloma, Relapsed/refractory, Secondary extramedullary disease, Daratumumab, Bendamustine