Outcomes and prognostic factors associated with relapse after haploidentical stem cell transplantation for paediatric T‐cell acute lymphoblastic leukaemia

The outcomes are poor for paediatric patients with T-cell acute lymphoblastic leukaemia (T-ALL) who relapse after haematopoietic stem cell transplantation (HSCT). However, studies focusing on paediatric patients with T-ALL following haploidentical HSCT (haplo-HSCT) are limited. We retrospectively identified a consecutive cohort comprising of 128 paediatric T-ALL after haplo-HSCT from 2642 consecutive ALL patients between January 2010 and June 2022. The 2-year overall survival and leukaemia-free survival were 67.77% ± 4.21% and 66.34% ± 3.82%, respectively, and the cumulative incidence of relapse (CIR) and non-relapse mortality were 33.82% ± 0.70% and 12.65% ± 0.46% respectively. According to the multivariate Cox regression analysis, CD34 cells, minimal residual disease (MRD) ≥0.01% before HSCT, chronic graft-versus-host disease (cGvHD) and cytomegalovirus were associated with relapse (p < 0.05). To develop a scoring system for stratifying patients, we combined the variables and stratified them into low (0-2 points) and high (3, 4) groups. Consequently, the 2-year CIR in low and high groups were 23.76% ± 1.83% and 48.22% ± 2.42% (p = 0.009), respectively. Children with T-ALL have poor long-term survival, and haplo-HSCT is a potent and safe treatment; however, the incidence of relapse is high. Eliminating pre-HSCT MRD, guaranteeing sufficient CD34 cells infusion and the occurrence of cGvHD and cytomegalovirus reactivation may benefit from relapse.