Allogeneic stem cell transplantation as immunotherapy for nonhematological cancers.

Over the past two decades biologic therapy has played an increasing role in the treatment of cancer. While this field is still early in its development, there now exists compelling evidence that the immune system is capable of detecting and eliminating cancer cells. Although the majority of immunotherapy approaches for metastatic cancer involve strategies designed to enhance autologous immunity, most would agree that the graft-versus-leukemia reaction induced following allogeneic stem cell transplantation represents modern day's most potent form of cancer immunotherapy. While allogeneic stem cell transplantation has gained recognition as a potentially curative "immunotherapy" for a growing number of different hematological malignancies, its efficacy in inducing antimalignancy effects against nonhematological cancers has only recently begun to be investigated. The historical basis, development, and preliminary clinical results of allogeneic stem cell transplantation as a form of immunotherapy for treatment refractory solid tumors are reviewed.