Stem cell transplantation for multiple myeloma: who, when, and what type?

Early randomized trials of high-dose chemotherapy with autologous stem cell rescue showed improved progression-free survival (PFS) over conventional chemotherapy. However, in the era of novel agents for myeloma in conjunction with the evolution of hematopoietic stem cell transplantation, many new questions arise. First, how can novel agents be incorporated into the transplant paradigm? Given the efficacy of new induction regimens, should transplant be delayed until relapse? Also, in the era of individualized medicine, chronologic age alone should not drive decisions regarding transplantation. Therefore, the feasibility and role of transplantation in older patients with myeloma is being studied. The controversy of transplant type (i.e., autologous compared with reduced intensity allogeneic transplant) remains unresolved. Several large international trials have demonstrated conflicting results in regard to an overall survival (OS) benefit with the allogeneic approach. The role of allogeneic transplant remains under study especially in the high-risk population, which has high relapse rates with traditional autologous approaches. Future directions to reduce relapse include post-transplantation consolidation and maintenance therapy with either approved agents or new agents and immunotherapy, either vaccine based or natural killer (NK) and T-cell based.