Long-term outcome of children with acute lymphoblastic leukemia after hematopoietic stem cell transplantation based on ex-vivo alpha-beta T cell depletion

Hematopoietic stem cell transplantation (HSCT) is a curative option for children with high-risk acute lymphoblastic leukemia (ALL). This retrospective single-center study analyzed 236 pediatric ALL patients in complete remission who underwent allogeneic HSCT using ex-vivo T cell depletion between 2012 and 2021. The majority received haploidentical grafts (n = 202), while the remainder received matched unrelated donor (MUD) grafts (n = 34). At four years, event-free survival (EFS) and overall survival (OS) were 57% and 67%, respectively. Total body irradiation (TBI)-based conditioning was associated with significantly lower relapse rates and superior EFS compared to chemotherapy-based regimens. Non-relapse mortality (NRM) was low (9%), with no significant difference between donor types. Pre-transplant minimal residual disease (MRD) positivity and transplantation beyond first complete remission were independently associated with higher relapse and inferior survival. Chronic GVHD incidence was lower in patients receiving abatacept and tocilizumab instead of ATG. These findings confirm the safety and efficacy of ex-vivo T cell-depleted HSCT in pediatric ALL, with outcomes comparable between haploidentical and MUD donors. TBI-based conditioning and MRD negativity remain key prognostic factors for improved outcome.