Comparison of HLA‐haploidentical donors with post‐transplant cyclophosphamide versus HLA‐matched unrelated donors in peripheral blood stem cell transplantation for acute myeloid leukaemia

Summary HLA‐haploidentical haematopoietic cell transplantation with post‐transplant cyclophosphamide (PTCy‐haplo) is emerging as an effective alternative due to donor availability and safety. We conducted a nationwide retrospective study comparing the outcomes of PTCy‐haplo with both anti‐thymocyte globulin (ATG)‐free and ATG‐administered matched unrelated donors (MUD) transplantation, using peripheral blood stem cells as the first transplantation for acute myeloid leukaemia (AML). Our study showed a lower and slower haematopoietic recovery and a higher incidence of infection‐related deaths after PTCy‐haplo than after MUD transplantation. In addition, we revealed an increased risk of acute and chronic graft‐versus‐host disease (GVHD) in ATG‐free MUD transplantation in comparison to PTCy‐haplo. For grades III–IV acute GVHD, the hazard ratio (HR) was 2.71 (95% CI, 1.46–5.01), and for extensive chronic GVHD, the HR was 3.11 (95% CI, 2.07–4.68). There was no significant difference regarding overall survival amongst the groups. In addition, GVHD‐free relapse‐free survival (GRFS) was lower in ATG‐free MUD transplantation than in PTCy‐haplo (HR, 1.46; 95% CI, 1.17–1.82). Notably, ATG‐administered MUD transplantation showed no significant difference in GRFS from PTCy‐haplo, negating the advantage of PTCy. Our results suggest that PTCy‐haplo could be viable for AML patients without an HLA‐matched related donor.