Outcomes and predictors of second haploidentical hematopoietic stem cell transplantation for pediatric acute leukemia relapsing after a first allograft.

BACKGROUND

The clinical efficacy and prognostic factors of haploidentical hematopoietic stem cell transplantation (haplo-HSCT) as a salvage approach for children with relapsed acute leukemia (AL) after a first allogeneic HSCT (allo-HSCT) remain unclear. This study aimed to evaluate the clinical efficacy, survival outcomes, and prognostic factors of second haploidentical HSCT in children with relapsed AL following prior allo-HSCT.

METHODS

This retrospective study included 40 pediatric patients (median age: 8.5 years) who underwent a second haplo-HSCT at two Chinese transplantation centers between January 2017 and December 2023. The primary endpoints were overall survival (OS) and leukemia-free survival (LFS); and secondary endpoints included cumulative relapse incidence and non-relapse mortality (NRM).

RESULTS

With a median follow-up of 16.0 months, 1- and 2-year OS rates were 77.8% and 65.5%, and LFS rates were 72.4% and 61.0%, respectively. The 2-year cumulative incidences of relapse and NRM were 26.6% and 15.1%, respectively. Multivariate analysis showed that B-cell acute lymphoblastic leukemia was associated with the most favorable 2-year OS (HR = 0.081, 95%CI: 0.007-0.877, P = 0.039). Grade III-IV acute GVHD occurred in 25.0% of patients, and chronic GVHD occurred in 50.0% (10.0% extensive).

CONCLUSIONS

These findings suggest that second haplo-HSCT with myeloablative conditioning may be a viable and effective salvage option for pediatric patients with relapsed AL lacking matched donors, possibly through graft-versus-leukemia effects. Future studies should incorporate targeted therapies and immune modulation strategies to improve outcomes in this high-risk population.