Unrelated Donor Vs Hla-Haploidentical Alpha/Beta T-Cell- And B-Cell-Depleted Hsct In Children With Acute Leukemia

Traditionally, hematopoietic stem cell transplantation (HSCT) from both HLA-matched related and unrelated donors (UD) has been used for treating children with acute leukemia (AL) in need of an allograft. Recently, HLA-haploidentical HSCT after alpha beta T-cell/B-cell depletion (alpha beta haplo-HSCT) was shown to be effective in single-center studies. Here, we report the first multicenter retrospective analysis of 127 matched UD (MUD), 118 mismatched UD (MMUD), and 98 alpha beta haplo-HSCT recipients, transplanted between 2010 and 2015, in 13 Italian centers. All these AL children were transplanted in morphological remission after a myeloablative conditioning regimen. Graft failure occurred in 2% each of UD-HSCT and alpha beta haplo-HSCT groups. In MUD vs MMUD-HSCT recipients, the cumulative incidence of grade II to IV and grade III to IV acute graft-versus-host disease (GVHD) was 35% vs 44% and 6% vs 18%, respectively, compared with 16% and 0% in alpha beta haplo-HSCT recipients (P<.001). Children treated with alpha beta haplo-HSCT also had a significantly lower incidence of overall and extensive chronic GVHD (P<.01). Eight (6%) MUD, 32 (28%) MMUD, and 9 (9%) alpha beta haplo-HSCT patients died of transplant-related complications. With a median follow-up of 3.3 years, the 5-year probability of leukemia-free survival in the 3 groups was 67%, 55%, and 62%, respectively. In the 3 groups, chronic GVHD-free/relapse-free (GRFS) probability of survival was 61%, 34%, and 58%, respectively (P<.001). When compared with patients given MMUD-HSCT, alpha beta haplo-HSCT recipients had a lower cumulative incidence of nonrelapse mortality and a better GRFS (P<.001). These data indicate that alpha beta haplo-HSCT is a suitable therapeutic option for children with AL in need of transplantation, especially when an allele-matched UD is not available.