Reduced-intensity versus myeloablative allogeneic transplantation.

Allotransplantation cures patients by cytoreduction and the graft-versus-tumor (leukemia; graft-versus-leukemia [GVL]) alloresponse; both eliminate residual disease. The spectrum of conditioning intensity influences toxicities and non-relapse mortality. The spectrum of tumor sensitivity to the GVL response influences relapse. Balancing tolerable toxicities (influenced by patients' performance status and comorbidities) is also influenced by the graft. Intense immunosuppression (for engraftment and graft-versus-host disease prevention) may constrain the immunologic potency of the graft and limit the antineoplastic capacity of the transplant, thus requiring more intense or more effective conditioning regimens to limit the risks of relapse and permit satisfactory disease-free survival.