Allogeneic hematopoietic cell transplantation from haploidentical donors with total body irradiation versus chemo-based regimens for adult AML patients in first complete remission. A study from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation (EBMT).

Adults with acute myeloid leukaemia (AML) receiving T-cell replete hematopoietic cell transplantation (HCT) from haploidentical donors are increasing. It is unknown whether a total body irradiation (TBI)-based regimen is associated with better survival than a chemotherapy (chemo)-based regimen. This is a retrospective analysis of AML patients in first complete remission who received a HCT from a haploidentical donor, from 2010 to 2022, reported to the ALWP of the EBMT database. Patients were divided into TBI vs. chemo-based regimens and stratified by transplant conditioning intensity (TCI): low (1-2) vs. intermediate/high (2.5-6). A total of 2309 patients (median age 56.8 years, range 18-82) were included. For patients with low TCI, multivariate analysis confirmed higher disease relapse with TBI (HR 1.49, 95% CI 1.03-2.16, p = 0.033) with respect to chemo, but lower NRM (HR 0.56, 95% CI 0.36-0.89, p = 0.013). In TCI intermediate/high, TBI was associated with a higher risk of NRM (HR 1.71, 95% CI 1.07-2.74, p = 0.026), inferior OS (HR 1.61, 95% CI 1.08-2.42, p = 0.02) and GRFS (HR 1.43, 95% CI 1.03-1.95, p = 0.034). The use of TBI in AML transplanted from haploidentical donors is feasible, although it does not appear to be associated with a survival advantage compared to chemotherapy-only regimens. Prospective clinical trials are warranted.