Total body irradiation plus fludarabine versus busulfan plus fludarabine as a myeloablative conditioning for adults with acute myeloid leukemia treated with allogeneic hematopoietic cell transplantation. A study on behalf of the Acute Leukemia Working Party of the EBMT.

Cyclophosphamide is frequently substituted with fludarabine (Flu) in conditioning regimens before allogeneic hematopoietic cell transplantation (allo-HCT). We aimed to compare retrospectively, total body irradiation (12 Gy) plus Flu (FluTBI12) versus busulfan (Bu) plus Flu (FB4) as a myeloablative conditioning before allo-HCT in patients with acute myeloid leukemia (AML). Out of 3203 patients who met the inclusion criteria, 109 patients treated with FluTBI12 and 213 treated with FB4 were included in a final matched-pair analysis. In both groups, median patient age was 41 years, first or second complete remission (CR1/CR2) proportion was 78%/22%, allo-HCT from an unrelated donor was performed in 78% of patients. The probabilities of leukemia-free survival and overall survival at 2 years in FluTBI12 and FB4 groups were 65% vs. 60% (p = 0.64) and 70% vs. 72% (p = 0.87), respectively. The cumulative incidence of relapse was 19% vs. 29% (p = 0.11), while non-relapse mortality was 16% vs. 11%, respectively (p = 0.13). There were no statistical differences in both acute and chronic graft-versus-host disease (GVHD) incidence. The probability of GVHD-free, relapse-free survival (GRFS) was 49% for both groups. FluTBI12 and FB4 are comparable myeloablative regimens before allo-HCT in AML patients transplanted in CR1 and CR2.