Outcome of allogeneic hematopoietic cell transplantation in adult acute lymphoblastic leukemia patients who underwent myeloablative TBI-free conditioning regimen.

Acute lymphoblastic leukemia (ALL) predominantly affects children but has poorer outcomes in adults. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a key consolidation therapy for high-risk patients, but the more commonly employed total body irradiation (TBI) regimen may be inaccessible in resource-limited settings, requiring alternative regimens. This retrospective study evaluated outcomes of 829 adult ALL patients who underwent HLA-matched allo-HSCT with a myeloablative, TBI-free regimen over two decades. The study compared overall survival (OS), disease-free survival (DFS), relapse incidence (RI), and non-relapse mortality (NRM) between pre- and post-2010 periods. Post-2010, 5-year OS improved from 38.3% to 48.1% (p = 0.0037), DFS from 36.6% to 42.0% (p = 0.027), and RI decreased from 47.5% to 40.8% (p = 0.012), with more notable improvements in patients ≥25 years. NRM remained stable (28.5% vs. 24.9%, p = 0.599). These findings suggest that a Busulfan-based, TBI-free regimen is a viable alternative, but further efforts are needed to reduce NRM and improve survival.