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Older patients with acute myeloid leukemia (AML) have high relapse risk and poor survival after allogeneic hematopoietic cell transplantation (HCT). Younger patients may receive myeloablative conditioning to mitigate relapse risk associated with high-risk genetics or measurable residual disease (MRD), but older adults typically receive reduced-intensity conditioning (RIC) to limit toxicity. To identify factors that drive HCT outcomes in older patients, we performed targeted mutational analysis (VAF≥2%) on diagnostic samples from 295 AML patients age 60 or older who underwent HCT in first complete remission, 91% of whom received RIC, and targeted duplex sequencing at the time of remission in 192 patients. In a multivariable model for leukemia-free survival (LFS) including baseline genetic and clinical variables, we defined patients with low (3-year LFS 85%), intermediate (55%), high (35%), and very high risk (7%). Prior to HCT, 79.7% of patients had persistent baseline mutations, including 18.3% with only DNMT3A or TET2 mutations (DT) and 61.4% with other mutations (MRDpositive). In univariable analysis, MRD-positivity was associated with increased relapse and inferior LFS compared with DT and MRDnegative patients. However, in a multivariable model accounting for baseline risk, MRD-positivity had no independent impact on LFS, likely due to its significant association with diagnostic genetic characteristics including MDS-associated gene mutations, TP53 mutations, and high-risk karyotype. In conclusion, molecular associations with MRD positivity and transplant outcomes in older AML patients are driven primarily by baseline genetics, and not by mutations present in remission. In this group of patients, where high-intensity conditioning carries substantial risk of toxicity, alternative approaches to mitigating MRD-associated relapse risk are required.

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