Long-term Outcomes of Allogeneic Hematopoietic Cell Transplantation in Patients With Relapsed/Refractory Multiple Myeloma

Background/Aim: Allogeneic (allo-) hematopoietic cell transplantation (HCT) may confer a survival advantage in a selected population of patients with relapsed and refractory multiple myeloma (R/R MM), however, additional data are needed to identify the patients who will benefit the most. Patients and Methods: Between January 2000 and December 2024, 32 patients with R/R MM underwent allo-HCT at the Asan Medical Center, Seoul, Korea, and were included in this retrospective study. Results: Before allo-HCT, complete remission (CR) achievement tended to be associated with better overall survival (OS) compared to partial response and refractory status (67.7% vs. 31.7% and 16.7% at 5 years, respectively, p=0.079). The OS rate was significantly higher in patients who underwent prior autologous (auto-) HCT compared to upfront allo-HCT (47.3% vs. 0% at 5 years, p=0.016). In multivariate analysis, upfront allo-HCT without previous auto-HCT was a significant adverse factor for OS [hazard ratio (HR)=6.248, 95% confidence interval (CI)=1.541-25.330, p=0.010]. In addition, the number of chemotherapy (≥3) before allo-HCT was a significantly independent adverse factor for OS (HR=2.854; 95%CI=1.071-7.602; p=0.035). Conclusion: In R/R MM after auto-HCT, allo-HCT for patients who attained CR following less than three lines of chemotherapy can still be a promising treatment option with long-term survival.