Stem cell transplantation: past, present and future.

The early attempts at human allogeneic marrow transplants in the 1950's and 1960's were largely unsuccessful. The probability of success has improved steadily in the past two decades. Cure rates now range from 90% for non-malignant diseases transplanted early to 15% for patients with advanced leukemia. Most marrow transplants have involved an HLA matched sibling donor but, more recently, a matched unrelated volunteer marrow donor can be found for many patients without a family donor. Current research is focused on new preparative regimens for elimination of malignant cells, better prevention of graft-versus-host disease, and the use of hematopoietic growth factors and cytokines. Autologous transplants, which use the patient's own marrow, are increasing, particularly for breast cancer. The hematopoietic stem cells are responsible for marrow regeneration after a transplant. Sufficient numbers of stem cells for transplantation can now be obtained from the peripheral blood after mobilization of these cells by chemotherapy or hematopoietic growth factors. Transplants can also be achieved using stem cells obtained from cord blood at the time of delivery, tissue typed, and cryopreserved for later use. A variety of technological advances has reduced the hospitalization time for transplant patients with a corresponding saving in cost.