The current status of hematopoietic stem cell transplantation for multiple myeloma

Multiple myeloma is often successfully controlled with conventional chemotherapy, but complete remissions are uncommon and cure is rare. High-dose therapy followed by autologous or allogeneic stem cells, employed for the treatment of multiple myeloma in the past 20 years, is promising as a means to increase remission rates and improve survival. Autologous transplants have not always demonstrated survival benefits in randomized studies because most of the patients transplanted relapse, while patients given conventional therapy can receive salvage transplants when they relapse. Efforts to improve the results of autologous transplant include targeted radiation, cytoprotective agents, tandem transplants, or post-transplant immunotherapy. Only allogeneic hematopoietic stem cell transplantation is potentially curative, due to a graft-versus-myeloma effect. While patients who receive either allogeneic or autologous stem cell transplants for multiple myeloma have similar 3-5 year survival, only allograft recipients appear to enjoy long-term disease-free survival. High transplant-related mortality associated with allogeneic stem cell transplantation is currently the major limitation to wider use of this potentially curative modality. Strategies designed to improve the therapeutic index of allografts include the use of nonablative conditioning regimens, peripheral blood cells rather than bone marrow, graft engineering, and targeted conditioning therapies such as bone-seeking radioisotopes.