Reduced-intensity versus conventional myeloablative conditioning allogeneic stem cell transplantation for patients with acute lymphoblastic leukemia: a retrospective study from the European Group for Blood and Marrow Transplantation.

This retrospective study assessed the outcome of 576 adult acute lymphoblastic leukemia patients aged ≥ 45 years, and who received a reduced-intensity conditioning (RIC; n = 127) or myeloablative conditioning (MAC; n = 449) allogeneic stem cell transplantation (allo-SCT) from a human leukocyte antigen-identical sibling while in complete remission. With a median follow-up of 16 months, at 2 years, the cumulative incidences of nonrelapse mortality and relapse incidence were 29% ± 2% (MAC) versus 21% ± 5% (RIC; P = .03), and 31% ± 2% (MAC) versus 47% ± 5% (RIC; P < .001), respectively. In a multivariate analysis, nonrelapse mortality was decreased in RIC recipients (P = .0001, hazard ratio [HR] = 1.98) whereas it was associated with higher relapse rate (P = .03, HR = 0.59). At 2 years, LFS was 38% ± 3% (MAC) versus 32% ± 6% (RIC; P = .07). In multivariate analysis, the type of conditioning regimen (RIC vs. MAC) was not significantly associated with leukemia-free survival (P = .23, HR = 0.84). Despite the need for randomized trials, we conclude that RIC allo-SCT from a human leukocyte antigen-identical donor is a potential therapeutic option for acute lymphoblastic leukemia patients aged ≥ 45 years in complete remission and not eligible for MAC allo-SCT.