Allogeneic hematopoietic cell transplantation for multiple myeloma.

Some patients with multiple myeloma (MM) who have undergone allogeneic hematopoietic stem cell transplants remain free of disease 5 to 13 years later-a major accomplishment for a malignancy that had been resistant to all investigational therapies. Although it will require longer follow-up to determine how many are truly cured, results for patients with MM transplanted from identical twins suggest that long-term progression-free survival is possible. While 3- to 5-year survival is similar after allogeneic or autologous stem cell transplant for MM, only allograft recipients appear to enjoy long-term disease-free survival, most likely due to an allogeneic graft-versus-myeloma (GVM) effect. The very high transplant-related mortality associated with standard allogeneic stem cell transplantation is currently the major limitation to wider use of this potentially curative treatment. The challenge for clinical investigators will be to reduce the incidence of posttransplant complications. Strategies include the use of nonablative conditioning for allografts, the administration of peripheral blood stem cells (PBSC) rather than bone marrow, and the application of more focused, targeted conditioning therapies such as bone-seeking radioisotopes.