A prospective randomized toxicity study to compare reduced‐intensity and myeloablative conditioning in patients with myeloid leukaemia undergoing allogeneic haematopoietic stem cell transplantation

Background To our knowledge, no randomized toxicity studies have been conducted to compare myeloablative conditioning ( MAC ) and reduced‐intensity conditioning ( RIC ) in allogeneic haematopoietic stem cell transplantation ( HSCT ). Methods Adult patients ≤60 years of age with myeloid leukaemia were randomly assigned (1 : 1) to treatment with RIC ( n  =   18) or MAC ( n  =   19) in this Phase II single‐centre toxicity study. Results There was a maximum median mucositis grade of 1 in the RIC group compared with 4 in the MAC group ( P  <   0.001). Haemorrhagic cystitis occurred in eight of the patients in the MAC group and none in the RIC group ( P  <   0.01). Results of renal and hepatic tests did not differ significantly between the two groups. RIC ‐treated patients had faster platelet engraftment ( P  <   0.01) and required fewer erythrocyte and platelet transfusions ( P  <   0.001) and less total parenteral nutrition ( TPN ) than those treated with MAC ( P  <   0.01). Cytomegalovirus ( CMV ) infection was more common in the MAC group (14/19) than in the RIC group (6/18) ( P  =   0.02). Donor chimerism was similar in the two groups with regard to CD 19 and CD 33, but was delayed for CD 3 in the RIC group. Five‐year transplant‐related mortality ( TRM ) was approximately 11% in both groups, and rates of relapse and survival were not significantly different. Patients in the MAC group with intermediate cytogenetic acute myeloid leukaemia had a 3‐year survival of 73%, compared with 90% among those in the RIC group. Conclusion Reduced‐intensity conditioning had several advantages compared with MAC , including less mucositis, less haemorrhagic cystitis, faster platelet engraftment, the need for fewer transfusions and less TPN , and fewer CMV infections. Both regimens were tolerated and TRM was low.