Prognosis of haploidentical hematopoietic stem cell transplantation in non-infant children with t(v;11q23)/MLL-rearranged B-cell acute lymphoblastic leukemia.

B-cell acute lymphoblastic leukemia (B-ALL) with MLL-rearrangements (MLL-r) is rare in pediatric patients (aged >1 year), and optimal treatment strategies remain unclear. This study aimed to retrospectively evaluate the clinical characteristics, outcomes, and effects of allogeneic hematopoietic stem cell transplantation (allo-HSCT) of 37 non-infant children with t(v;11q23)/MLL-r B-ALL. Their 4-year overall survival (OS), event-free survival (EFS), and cumulative incidence of relapse (CIR) were 69.8 %, 58.2 %, and 39.1 %, respectively, and differed significantly between patients receiving allo-HSCT (18/19 cases received haploidentical [haplo]-HSCT) at the first complete remission (HSCT at CR1, n = 19; 87.4 %, 89.5 % and 5.3 %) and those continuing consolidation therapy (Non-HSCT at CR1, n = 18; 52.2 %, 25.9 %, and 74.1 %, respectively), and the p values were 0.022, <0.001 and <0.001, respectively. Of the 13 patients experiencing relapse during consolidation chemotherapy, the five continuing with chemotherapy only died within 44 months, and the eight patients opting for allo-HSCT after CR2 had a 4-year OS of 57.1 %. Multivariate analysis revealed HSCT at CR1 as the only independent protective factor for OS, EFS, and CIR. The present results indicate that allo-HSCT (especially haplo-HSCT) at CR1 may decrease the relapse rate and improve the prognosis of non-infant children with t(v;11q23)/MLL-r B-ALL.