Autologous/Allogeneic Hematopoietic Cell Transplantation versus Tandem Autologous Transplantation for Multiple Myeloma: Comparison of Long-Term Postrelapse Survival

We compared postrelapse overall survival (OS) after autologous/allogeneic (auto/alto) versus tandem autologous (auto/auto) hematopoietic cell transplantation (HCT) in patients with multiple myeloma (MM). Postrelapse survival of patients receiving an auto/auto or auto/alto HCT for MM and prospectively reported to the Center for International Blood and Marrow Transplant Research between 2000 and 2010 were analyzed. Relapse occurred in 404 patients (72.4%) in the auto/auto group and in 178 patients (67.4%) in the auto/alto group after a median follow-up of 8.5 years. Relapse occurred before 6 months after a second HCT in 46% of the auto/ allo patients, compared with 26% of the auto/auto patients. The 6-year postrelapse survival was better in the auto/alto group compared with the auto/auto group (44% versus 35%; P=.05). Mortality due to MM was 69% (n=101) in the auto/allo group and 83% (n=229) deaths in auto/auto group. In multivariate analysis, both cohorts had a similar risk of death in the first year after relapse (hazard ratio [FIR],.72; P=.12); however, for time points beyond 12 months after relapse, overall survival was superior in the auto/allo cohort (HR for death in auto/auto=1.55; P=.005). Other factors associated with superior survival were enrollment in a clinical trial for HCT, male sex, and use of novel agents at induction before HCT. Our findings shown superior survival after relapse in auto/allo HCT recipients compared with auto/auto HCT recipients. This likely reflects a better response to salvage therapy, such as immunomodulatory drugs, potentiated by a donor-derived immunologic milieu. Further augmentation of the post-allo-HCT immune system with new immunotherapies, such as monoclonal antibodies, checkpoint inhibitors, and others, merit investigation. (C) 2017 American Society for Blood and Marrow Transplantation.