Hematopoietic stem cell transplants for multiple myeloma

Standard chemotherapy with melphalan-prednisone or a combination of alkylating agents has not extended the overall survival of patients with multiple myeloma during the last 30 years and strictly defined complete remissions (CR) are exceedingly rare. The early mortality with conventional therapy varies between 2 and 10 percent. A substantial increase in the dose of melphalan (100-140 mg/m2) has resulted in a 30-45% CR rate in newly diagnosed patients and an overall survival advantage of approximately 1 year. However, treatment related morbidity and mortality, due to prolonged cytopenia was unacceptably high. Based on these findings the dose intensity was further increased by either escalating melphalan to 200 mg/m2 or by adding total body irradiation, while at the same time providing stem cell support to shorten the duration of cytopenia. Autologous transplants, especially with peripheral blood stem cells and hematopoietic growth factors, can now be performed safely up to the age of 70 with a low transplant-related mortality (2-10%). A CR is attained in approximately 50% of previously untreated patients and 10-20% of refractory cases. Overall survival of newly diagnosed and refractory patients treated with autotransplants appears superior to that of patients receiving conventional chemotherapy. Therefore, autotransplantation should be considered as a treatment option in all patients with multiple myeloma at least up to the age of 65. Despite these encouraging findings, most myeloma patients ultimately relapse and the survival curves do not suggest that autotransplantation as currently performed is a curative approach in a substantial proportion of patients. Further improvement with autotransplants should be achieved by providing tumor-free grafts and by introducing post-transplantation manipulations, aimed at eradicating minimal residual disease.