Conditioning regimens for allogeneic stem cell transplants.

In addition to providing cytoreduction at myeloablative dose intensity, conditioning regimens for allogeneic transplantation are designed to immunosuppress the recipient to permit donor lymphohematopoietic engraftment and thereby establish a graft-versus-malignancy effect. Increased confidence in the potency of this allogeneic graft-versus-malignancy effect, together with the need to reduce dose intensity to make transplantation safer and more widely applicable in older patients, has led to a conceptual revolution in conditioning regimen design. Novel nonmyeloablative transplant conditioning treatments have low regimen-related toxicity and low transplant-related mortality. The transplants confer a graft-versus-malignancy effect in myeloid and lymphoid malignancies and in metastatic renal cell cancer. Future prospects are for low toxicity conditioning regimens combined with specific antileukemia or antitumor intensification with radioconjugated or unmodified antibodies and the application of highly immunosuppressive but low toxicity conditioning regimens for mismatched transplants.