Background: Over the last two decades, umbilical cord blood (UCB) and haploidentical transplantation (HaploHSCT) have emerged as alternative sources of hematopoietic stem cell for allogeneic transplantation. There are few retrospective studies and no prospective studies comparing both types of alternative transplantation in pediatric patients.

Results: We analyzed the data of 134 children with hematological malignancies who received a hematopoietic stem cell transplantation from a single umbilical cord blood (UCB) (n = 42) or an "ex-vivo" T-cell depleted transplant from a haploidentical-related donor (HaploHSCT) (n = 92) between 1996 and 2014. Hematological recovery was faster after HaploHSCT than the UCB transplant group (median times to neutrophil and platelet recovery: 13 vs. 16 days, 10 vs. 57 days, respectively) (P < 0.001). The HaploHSCT group had a significantly early immune reconstitution based on NK and CD8+ T cells compared with the UCB group. However, after the first year post-transplantation, HaploHSCT had a lower number of CD4+ T and B lymphocytes compared with the UCB transplant recipients. The cumulative incidence of TRM was 29 ± 8% in the HaploHSCT group versus 40 ± 5% in the UCB group. Relapse incidence was 21 ± 7% in the HaploHSCT group and 19 ± 8% in the UCB group. Probability of DFS was 58 ± 8% in the HaploHSCT group versus 40 ± 9% in the UCB group (P = 0.051).