Outcomes of adults with acute myelogenous leukemia in remission given 550 cGy of single-exposure total body irradiation, cyclophosphamide, and unrelated donor bone marrow transplants

On the basis of observations from dog models and human studies, we hypothesized that a low-dose (550 cGy), single-exposure total body irradiation (TBI)-based regimen would result in improved survival when given to adult patients with acute myelogenous leukemia (AML) who were undergoing unrelated donor bone marrow transplantation in complete remission (CR). The regimen consisted of single exposure (550 cGy) of TBI given at a high dose rate (30 cGy/min) and cyclophosphamide. Graft-versus-host disease prophylaxis consisted of cyclosporine, methotrexate, and corticosteroids. Thirty-two consecutive adult patients (median age, 47 years) with AML in CR (15 in CR 1 and 17 in CR ≥2) were treated. Sixteen patients (50%) were alive and in remission at last follow-up (median, 2.2 years; range, 0.6-4.0 years). Kaplan-Meier estimates of overall and leukemia-free survival at 3 years were 55% ± 14% (mean ± SE) and 57% ± 14% in CR 1 patients and were both 39% ± 12% in CR ≥2 patients. Transplant-related mortality was 13% for patients in CR 1 and 41% for those in CR ≥2. Only 1 patient (3%) experienced fatal regimen-related organ toxicity, and only 1 had grade III or IV acute graft-versus-host disease. Graft failure was not observed. Relapse occurred in 22% of patients. This low-dose (550 cGy), single-exposure TBI-based regimen resulted in good survival and a low risk of fatal regimen-related organ toxicity in adult patients with AML who underwent unrelated donor bone marrow transplantation in CR.