Beelen DW, Trenschel R, Stelljes M, et al. - Researchers appraised the efficacy and safety of conditioning with treosulfan plus fludarabine vs reduced-intensity busulfan plus fludarabine before allogeneic haemopoietic stem cell transplantation (HSCT) in older or comorbid patients with acute myeloid leukemia or myelodysplastic syndrome via performing an open-label, randomized, non-inferiority, phase 3 trial in 31 transplantation centres in France, Germany, Hungary, Italy, and Poland. Patients were eligible for participation if they were 18–70 years, had acute myeloid leukaemia in first or consecutive complete haematological remission (blast counts < 5% in bone marrow) or myelodysplastic syndrome (blast counts < 20% in bone marrow), Karnofsky index of 60% or higher, and were indicated for allogeneic HSCT but estimated to be at an augmented risk for standard myeloablative preparative regimens based on age (≥ 50 years), an HSCT-specific comorbidity index of more than 2, or both. They included 476 patients in this randomized trial; in the busulfan group, 240 patients received treatment and transplantation, and in the treosulfan group, 221 received treatment and 220 transplanation. Findings suggest the noninferiority of treosulfan to busulfan when used in combination with fludarabine as a conditioning regimen for allogeneic HSCT for older or comorbid patients with acute myeloid leukemia or myelodysplastic syndrome. Patients treated with the treosulfan–fludarabine regimen exhibited improved outcomes, which support its potential to become a standard preparative regimen in this population.