Effects of consolidation therapy with autologous hematopoietic stem cell transplantation after BCMA-CAR T-cell therapy on the survival of patients with relapsed or refractory multiple myeloma

Despite the success of chimeric antigen receptor (CAR) T-cell therapy for relapsed or refractory multiple myeloma (RRMM), failure after CAR T-cell therapy remains an unmet medical need. An effective consolidation therapy after CAR T-cell therapy may improve the prognosis of RRMM. To investigate the effects of consolidation therapy with autologous hematopoietic stem cell transplantation (AHCT) after B-cell maturation antigen (BCMA)-targeted CAR T-cell therapy on the prognosis of RRMM patients. This retrospective study included 39 RRMM patients who received BCMA-targeted CAR T-cell therapy. Basic clinical, therapy, and outcome data were collected, and factors associated with survival were analyzed. Among the 39 RRMM patients included in the study, 15 had high-risk cytogenetics and 11 had extramedullary disease (EMD). All 39 patients reached peak CAR T-cell expansion within 28 days after infusion. Twenty-six patients developed cytokine release syndrome, including 12 grade 1 and 14 grade 2 cases. Survival analysis revealed that high-risk cytogenetics, high tumor load (International Staging System [ISS] stage III), and EMD were negatively associated with progression-free survival (PFS) and overall survival (OS). Thirteen patients received consolidation AHCT therapy 50-276 days after CAR T-cell therapy, with a median interval of 92 days. No serious complications occurred after consolidation AHCT. Survival analysis showed that consolidation AHCT effectively improved OS and PFS over maintenance chemotherapy. Moreover, Cox regression analysis identified low tumor load (ISS stage I/II) and consolidation AHCT as independent predictors of superior PFS and OS and high-risk cytogenetics as an independent risk factor for poor PFS. Consolidation AHCT after CAR T-cell therapy in RRMM patients can improve patient survival.