Allogeneic Stem Cell Transplantation in Multiple Myeloma

SIMPLE SUMMARY: Due to its graft-versus-myeloma effect, allogeneic hematopoietic stem cell transplantation (allo-SCT) can enable long-term survival or even cure in carefully selected patients with multiple myeloma (MM), but remains controversial due to its relevant treatment-related toxicity. Current data suggest that allo-SCT should be considered in young MM-patients without relevant comorbidities in case of a high-risk constellation according to cytogenetics or stage, primarily as part of a tandem approach with autologous-SCT followed by allo-SCT and early in the course of the disease. Prospective studies are warranted, due to a suspected synergism especially those including new immunotherapeutic approaches for induction, conditioning and maintenance therapy. ABSTRACT: The development of new inhibitory and immunological agents and combination therapies significantly improved response rates and survival of patients diagnosed with multiple myeloma (MM) in the last decade, but the disease is still considered to be incurable by current standards and the prognosis is dismal especially in high-risk groups and in relapsed and/or refractory patients. Allogeneic hematopoietic stem cell transplantation (allo-SCT) may enable long-term survival and even cure for individual patients via an immune-mediated graft-versus-myeloma (GvM) effect, but remains controversial due to relevant transplant-related risks, particularly immunosuppression and graft-versus-host disease, and a substantial non-relapse mortality. The decreased risk of disease progression may outweigh this treatment-related toxicity for young, fit patients in high-risk constellations with otherwise often poor long-term prognosis. Here, allo-SCT should be considered within clinical trials in first-line as part of a tandem approach to separate myeloablation achieved by high-dose chemotherapy with autologous SCT, and following allo-SCT with a reduced-intensity conditioning to minimize treatment-related organ toxicities but allow GvM effect. Our review aims to better define the role of allo-SCT in myeloma treatment particularly in the context of new immunomodulatory approaches.