Impact of Conditioning Intensity on Survival in Adult Patients (< 65 Years) With Acute Myeloid Leukemia Receiving Antithymocyte Globulin and Post-Transplantation Cyclophosphamide Based GVHD Prophylaxis.

Introduction: Myeloablative conditioning (MAC) for acute myeloid leukemia (AML) improves disease control by reducing relapse risk but is associated with higher non-relapse mortality (NRM). Reduced-intensity conditioning (RIC) aims to minimize toxicity but raises concerns about higher relapse rates. This study evaluates the impact of RIC versus MAC in AML patients under 65 years receiving GVHD prophylaxis with antithymocyte globulin, post-transplant cyclophosphamide, and cyclosporine.

Methods: We retrospectively analyzed 322 AML patients undergoing allogeneic HCT with uniform GVHD prophylaxis. Propensity score matching (PSM) was applied to adjust for baseline differences.

Results: In the matched cohort, 2-year overall survival (OS) did not differ significantly between RIC and MAC recipients (64.4% vs. 66.9%, p = 0.56). Relapse-free survival (RFS) at 2 years was 65.0% for MAC and 52.7% for RIC (p = 0.20). Two-year NRM was 19.4% for MAC and 19.1% for RIC (p = 0.84). Improved RFS was associated with non-high-risk DRI (HR: 0.39, p = 0.008), whereas conditioning intensity had no significant effect (HR: 0.98, p = 0.97). NRM was higher among patients with KPS < 90 (HR: 3.63, p = 0.01), with no significant impact observed from conditioning intensity (HR: 1.44, p = 0.43).

Conclusion: In a relatively younger cohort, conditioning intensity did not significantly impact survival, and MAC was not associated with increased NRM.