Stem Cell Transplantation
The future of stem cell transplantation as an effective cancer therapy remains promising. This treatment modality allows many patients with a variety of malignancies a greater chance of cure or prolonged remission when compared with standard chemotherapy.
There are now two prospective randomized controlled trials that show survival benefit when myeloma patients receive high dose chemotherapy and autologous stem cell transplantation as part of their initial treatment when compared to conventional therapy. In the French multi-center study (NEJM 1996; 91-97,) the patients treated with a transplant had an estimated five-year survival rate of 52 percent compared with 12 percent for patients treated with standard chemotherapy. In the British multi-center study (NEJM 2003; 1875-83) the median survival for transplant patients was 54 months compared with 42 months in the standard therapy arm.
Nonmyeloablative Allogeneic Transplants ("Mini Transplants")
Allogeneic stem cell transplantation is recognized as the most effective therapy for many leukemias and lymphomas. Research reveals that the curative potential of this therapy is not so much the chemotherapy and/or radiation that is given before the transplant (the "conditioning regimen"), but rather due to the "graft versus leukemia effect" exerted by the new immune system. For years, older patients, or patients with co-morbidities were not considered eligible for a conventional transplant because of the significant toxicities of the conditioning regimen. Over the last several years, (coinciding with the advent of lymphotoxic purine analog drugs) investigators have shown that much less toxic-conditioning regimens can be used that still facilitate engraftment of donor cells. This breakthrough offers a chance for cure to many patients with hematologic malignancies who previously had no chance at such an outcome.
As an understanding of immunogenic targets on tumor cells grows, stem cell transplant specialists will one day expand populations of allogeneicT-lymphocytes that are targeted directly against tumor antigens. This will allow full "graft versus tumor effect" without any graft versus host disease. Finally, there is an increasing body of data in animals and in humans that the adult hematopoeitic stem cell can actually differentiate into a wide range of tissues. Possibilities exist for the treatment of spinal cord injuries with stem cells in the future.