Outcomes of haploidentical stem cell transplantation in pediatric Philadelphia chromosome-like B-cell acute lymphoblastic leukemia in the era of immunotherapy

Reports of pediatric Ph-like acute lymphoblastic leukemia (ALL) after hematopoietic stem cell transplantation (HSCT) have been rare, especially in the immunotherapy era. Therefore, we retrospectively collected 56 pediatric Ph-like ALL who underwent haploidentical HSCT (haplo-HSCT) between January 2017 and June 2025. The 4-year overall survival (OS) and leukemia-free survival (LFS) were 90.8% (95% CI 83.4%-98.8%) and 73.6% (95% CI, 62.5%-86.5%), respectively. The cumulative incidence of relapse and non-relapse mortality was 17.6% (95% CI, 8.5%-29.2%) and 1.82% (95% CI, 0.145%-8.57%), respectively. Grade III-IV acute graft-versus-host disease (GVHD) was 9.85% (95% CI, 3.55%-20%), and moderate-to-severe chronic GVHD was 14.2% (95% CI, 6.15%-25.5%). Finally fourteen patients experienced molecular relapse, and four died of relapse in total. One died of severe pneumonia. EBV infection after HSCT may be associated with inferior LFS. Overall, this cohort showed a favorable survival in Ph-like patients after haplo-HSCT.