Newly diagnosed multiple myeloma patients treated with tandem auto‐allogeneic stem cell transplant have better overall survival with similar outcomes at time of relapse compared to patients who received autologous transplant only

Abstract Background Long‐term survival in patients progressing after tandem autologous‐allogeneic stem cell transplant (SCT) has been reported, suggesting a persistent graft‐vs‐myeloma (GvM) effect even after post‐transplant progression. Methods In order to confirm this observation, we updated the results of our previously published cohort of 92 newly diagnosed myeloma patients who received tandem transplant and compared them with 81 contemporary patients who received autologous transplant only. Results With a median follow‐up of 13.1 and 10.2 years, respectively, median overall survival (OS) in the tandem group has not been reached, compared with 6.1 years after auto‐SCT ( P ≤ .001). Disease progression occurred less frequently after tandem transplant, with an estimated 10‐year cumulative incidence of 49% vs 76% ( P ≤ .001). Cumulative incidence of extensive chronic graft‐vs‐host disease (cGVHD) was high at 83%, with modest benefits on OS (60% vs 49%, P = .550) but sharp improvement of progression‐free survival (PFS; 55% vs 10%, P = .002) at 10 years associated with development of cGVHD. After first progression, median OS was 5.8 years in tandem and 5.2 years in the auto‐group ( P = .062); median PFS was also similar. Conclusion Despite confirmation of better outcomes after upfront tandem transplant, our data do not support persistence of a strong, clinically significant graft‐vs‐myeloma effect after first progression, emphasizing the need to better characterize the GvM effect.