Abstract:Objective To explore the possible predictors and the impact on efficacy of the development of cytokine release syndrome（CRS）in relapsed/refractory multiple myeloma（R/R MM）patients who accepted chimeric antigen receptor T（CAR-T）cell therapy. Methods Thirty-three patients who received CAR-T cell therapy for R/R MM in the Department of Hematology，Affiliated Hospital of Nantong University from April 2018 to September 2023 were retrospectively analyzed. According to the grade of CRS，the patients were divided into grade 0-1 group（n=13）and grade 2-4 group（n=20）. The possible predictive indexes of the development of CRS and the impact on the efficacy were analyzed. Results Overall response rate of CAR-T cell therapy reached 81.8% while 17 patients relapsed. There were 25 cases（75.8%）of patients developed CRS，with 5 cases in grade 1，18 cases in grade 2，and 1 case in grade 3 and 4，respectively. The pre-infusion prurie-Salmon（DS）staging in patients who developed grade 2-4 CRS was mostly stage Ⅲ（P=0.013）. The recurrence rate of grade 2-4 CRS patients was slightly higher than that of grade 0-1 CRS patients，but the difference was not statistically significant［55.0%（11/20）vs 46.2%（6/13），P=0.728］. There was no statistically significant difference in PFS between grade 1 and grade 2 CRS patients（P=0.12），but the median PFS in grade 2 CRS patients was significantly shorter than that in grade 1 CRS patients（31.5 months vs 13.6 months）. Conclusion CAR-T cell therapy for R/R MM is more likely to relapse although highly efficient，and patients who developed grade 2-4 CRS had later DS staging before CAR-T therapy. The development of grade 2 CRS may shorten PFS.