Type of prior genotoxic insult determines the genomic characteristics of therapy-related acute myeloid leukemia.

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7515 Background: Therapy-related AML (tAML) is a long-term complication of cytotoxic cancer therapy. It is characterized by adverse genetics and inferior survival outcomes when compared to de novo AML. A proposed mechanism in tAML pathogenesis includes treatment-induced selection of clones harboring pre-existing mutations (i.e. clonal hematopoiesis, CH). We hypothesize that genotoxic therapies used to treat prior malignancy drive leukemogenesis through different mechanisms leading to unique clonal compositions. Methods: AML patients (pts) treated at The Ohio State University between 2015-2018 were included. Genetic profiling was performed using Miseq Illumina platform with a 49-gene targeted sequencing panel at our clinical laboratory. Results: We studied 337 AML pts (Table), of whom 53% had smoking history. Mutations involving ASXL1 were more common in smokers vs non-smokers (14% vs 5.8%, p= .001), while JAK2 mutations were more common in non-smokers (8% vs 1.2%, p= .003). Regarding specific genotoxic therapies and mutations in tAML, we investigated common CH-associated mutations including DNMT3A, TET2, and ASXL1 (DTA mutations). In tAML pts, those exposed to radiotherapy experienced a higher frequency of DTA (52% vs 27%, p= .05), NPM1 (21% vs 0%, p= .002), and SRSF2 (15% vs 0%, p= .01) mutations, and conversely, a lower incidence of TP53 mutations (21% vs 46%, p= .04). Pts with history of cytotoxic chemotherapy had a lower incidence of DTA mutations, including those who received platinum agents (8% vs 49%, p= .005) and taxanes (7% vs 52%, p< .001), but had a higher incidence of TP53 mutations (75% vs 25%, p< .001 for platinum; 53% vs 25%, p= .04 for taxanes). Similarly, alkylators and anthracyclines were associated with lower incidence of DNMT3A (0% vs 20%, p= .009) and ASXL1 (0% vs 12.5%, p= .04) mutations. Conclusions: Different genotoxic agents demonstrate unique effects in leukemia development. Our data suggest that CH clones with DTA mutations may be enriched with smoking and radiotherapy, while cytotoxic chemotherapy may confer a higher incidence of TP53 mutations. Given the adverse prognosis of TP53 mutated AML, identification of pre-existing CH clones might influence treatment selection in solid tumor pts receiving anticancer therapy. [Table: see text]