A uniform conditioning regimen of busulfan, fludarabine, and antithymocyte globulin for allogeneic haematopoietic cell transplantation from haploidentical family, matched sibling, or unrelated donors—A single‐centre, prospective, explorative study

In a prospective, explorative study, the donor‐source difference of haploidentical family (HF), matched sibling (MS), and unrelated donors (UD) was evaluated for the outcome of haematopoietic cell transplantations (HCT) in 101 patients with acute myeloid leukaemia (AML) in complete remission (CR). To eliminate compounding effects, a uniform conditioning regimen containing antithymocyte globulin (ATG) was used. After transplantation, there was a significantly higher cumulative incidence of acute graft‐versus‐host disease (GVHD) in HF‐HCT patients (49%, 7%, and 16% for HF‐, MS‐ and UD‐HCT respectively; p < 0.001). A quarter of acute GVHD cases observed in HF‐HCT patients occurred within three days of engraftment and were characterized by diffuse skin rash, fever, weight gain, and hypoalbuminaemia. This peri‐engraftment acute GVHD was not observed in MS‐HCT or UD‐HCT patients. Additionally, a significantly higher proportion of HF‐HCT patients achieved complete donor chimaerism in the peripheral mononuclear cells at one month (88%, 46%, and 69% for HF‐, MS‐ and UD‐HCT respectively; p = 0.001). There was no significant difference in engraftment, chronic GVHD, leukaemia recurrence, non‐relapse mortality, and patient survival. In patients with AML in CR who received HCT using ATG‐containing conditioning, stronger donor–patient alloreactivity was observed in HF‐HCT, in terms of increased acute GVHD and higher likelihood of complete donor chimaerism.