Multiple myeloma: role of allogeneic transplantation.

An estimated 14,600 new cases of multiple myeloma will be diagnosed in the United States in 2002. Multiple myeloma remains an incurable disease despite significant improvements in complete response rates and overall survival through the use of autologous stem cell transplantation. Allogeneic transplantation offers the advantage of a tumor-free graft and a graft-vs-myeloma effect but has been associated with a high mortality rate from transplant-related complications-primarily graft-vs-host disease (GVHD). As immunotherapy for patients with relapsed myeloma, donor lymphocyte infusion has resulted in response rates of over 50%, but many of these responses are not durable. In addition, donor lymphocyte infusion is associated with a significant risk of moderate-to-severe GVHD. In an attempt to decrease the high transplant-related mortality of conventional allogeneic transplants and to employ the proven efficacy of immunoreactive donor T lymphocytes, the use of nonmyeloablative transplants or "mini-transplants" is increasing. This approach has succeeded in significantly reducing transplant-related mortality but still may not be sufficient in producing long-term remissions or cures in myeloma patients. A combination of an autologous transplant (to achieve maximal cytoreduction) and a mini-transplant with donor lymphocyte infusion (for the immunoablative effect of alloreactive T lymphocytes) followed by maintenance therapy (thalidomide [Thalomid], steroids, cytokines, vaccines) for long-term immunomodulation is being investigated as a potential cure for this challenging disease.