Haploidentical HSCT with post transplantation cyclophosphamide versus unrelated donor HSCT in pediatric patients affected by acute leukemia

T-cell replete hematopoietic stem cell transplantation (HSCT) from a haploidentical donor followed by high doses of cyclophosphamide has been demonstrated to provide the best chances of a cure for many children in need of an allograft but who lack both a sibling and an unrelated donor. In this study we retrospectively compared the outcome of pediatric patients undergoing T-replete haploidentical HSCT (Haplo) for acute leukemia with those undergoing transplantation from unrelated HLA-matched donor (MUD) and HLA mismatched unrelated donor (MMUD) from 2012 to 2017 at our Center. Both univariable and multivariable analyses showed similar 5-year overall survival rates for MUD, MMUD, and Haplo patients: 71% (95% CI 56-86), 72% (95% CI 55-90), and 75% (95% CI 54-94), respectively (p = 0.97). Haplo patients showed reduced event-free survival rates compared to MUD and MMUD patients: 30% (95% CI 12-49) versus 70% (95% CI 55-84) versus 53% (95% CI 35-73), respectively (p = 0.007), but these data were not confirmed by a multivariable analysis. Non-relapse mortality (NRM) and relapse incidence (RI) were similar for the three groups. Therefore, our data confirm that Haplo is a suitable clinical option for pediatric patients needing HSCT when lacking both an MUD and an MMUD donor.