Patients are randomized to one of two reduced intensity conditioning (RIC) regimens: the combination of fludarabine (30 mg/m^2/day, days -6 to days -2, the total dase is 150 mg/m^2) and busulfan (3.2 mg/kg/day, days -3 to days -2, the total dose is 6.4 mg/kg) (Flu/Bu) or fludarabine (30 mg/m^2/day, days -6 to days -2, the total dose is 150 mg/m^2) and melphalan (70 mg/m^2/day, days -3 to days -2, the total dose is 140 mg/m^2) (Flu/Mel). A total of 200 patients (100 to each arm) will be recruited in this study over a period of two years. Patients will be followed for up to 18 months from allogeneic hematopoietic stem cell transplantation.
The goal of this clinical trial is to compare outcomes of two reduced intensity conditioning (RIC) regimens (fludarabine plus busulfan and fludarabine plus melphalan) in allogeneic hematopoietic stem cell transplantation (HSCT) for acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) patients. The main questions it aims to answer are:~The safety of two reduced intensity conditioning (RIC) regimens (fludarabine plus busulfan and fludarabine plus melphalan) in allogeneic hematopoietic stem cell transplantation for adult AML/MDS patients with HCT-CI≥3 or aged ≥55 years.~The efficacy of two reduced intensity conditioning (RIC) regimens (fludarabine plus busulfan and fludarabine plus melphalan) in allogeneic hematopoietic stem cell transplantation for adult AML/MDS patients with HCT-CI≥3 or aged ≥55 years.~Participants will be randomized to one of two reduced intensity conditioning (RIC) regimens (fludarabine plus busulfan and fludarabine plus melphalan)