Busulfan-cyclophosphamide vs fludarabine-busulfan for allogeneic transplant in acute myeloid leukemia

Busulfan and cyclophosphamide (BuCy) is the standard myeloablative conditioning regimen for patients with acute myeloblastic leukemia (AML) undergoing allogeneic hematopoietic stem-cell transplantation (allo-HSCT). Fludarabine and busulfan (FluBu) conditioning seems to have similar efficacy with less toxicity.

Descriptive retrospective study conducted on patients with AML who underwent geno-identical allo-HSCT between January 2011 and December 2022. Patients received a myeloablative conditioning with either BuCy2 orFluBu4. The objective was to compare the efficacy and safety of this regimens.

A total of 113 adult patients were included. Conditioning regimen was BuCy2 in 81% of patients (n = 92) and FluBu4 in 19% of patients (n = 21). The 3-year estimated overall survival and event-free survival were 65% vs 81% (p = 0.19) and 58% vs 76% (p = 0.18) in BuCy2 and FluBu4 regimens, respectively. GVHD-Relapse Free Survival was better in FluBu4 group compared to BuCy2 group (28% vs 41%, p = 0.03). The Cumulative incidence of relapse and non-relapse mortality were 38% vs 14% (p = 0.17) and 15% vs 10% (p = 0.57) in BuCy2 and FluBu4, respectively. Both regimens yield comparable toxicities.

Myeloablative FluBu4 conditioning appeared to achieve clinical outcomes similar to BuCy2 and may be considered as a possible alternative for patients at high risk of NRM.