The role of allogeneic stem cell transplantation in multiple myeloma in the new drug era

Multiple myeloma is considered to be an incurable disease. Despite the introduction of autologous stem cell transplantation and more recently novel agents, such as lenalidomide and bortezomib, allogeneic stem cell transplantation still induces the highest rate of clinical complete and molecular remission and it can induce long-term freedom from disease in about 30-40% of the cases. The major disadvantage is the higher morbidity and mortality of this approach, which are caused by immunological complications after transplantation such as graft-versushost disease and infectious diseases. However, donor derived T-cells and may also NK cells can also induce a graft versus myeloma effect. This graft versus tumor effect seems to be less strong than in other hematological diseases, but donor-lymphocyte infusions given to patients who relapsed after allogeneic stem cell transplantation can induce response rate between 40% and 67%. Allogeneic stem cell therapy studies suggest that achievement of molecular remission after transplantation is associated with long-term freedom from disease. Modern myeloma therapy approaches should lower the therapy related mortality of allogeneic stem cell transplantation and use this immunological platform for immunological- or drug based therapies post transplantation to achieve molecular remission and ultimately cure.