Abstract PS1-07-21: Germline Genetic Variants and Risk of Acute Radiation Dermatitis in Patients Receiving Curative-Intent Radiation Therapy for Breast Cancer

Abstract Background: Multigene panel testing has increased the detection of pathogenic germline variants (PV) in patients with breast cancer. The impact of PVs and variants of unknown significance (VUS) on toxicity and clinical outcomes has largely been studied in patients with BRCA1 or BRCA2 mutations, with few data on patients with other genetic alterations. In addition, few studies have characterized the impact of VUS on toxicity and/or outcomes. At our institution, a prospective Precision Medicine study was started to characterize germline and somatic mutations in breast cancer patients. Here, we present a preliminary analysis of acute toxicity rates in breast cancer patients treated with curative intent radiation therapy based on germline mutation status. Materials/Methods: This retrospective, single-institution study utilized the Precision Medicine database at our institution to identify breast cancer patients with available genetic data. Among 4400 patients with stage I-IV breast cancer, 900 received curative-intent breast radiotherapy (RT). Clinicodemographic information, RT parameters, and germline mutation status - characterized as PV, VUS, or benign - were extracted from the database. RT toxicity was prospectively documented in the electronic medical record (EMR) during the study period. The primary endpoint was the incidence of acute grade 2 or higher radiation dermatitis (G2RD). Associations between germline mutational status and toxicity rates were evaluated using the chi-square test, with significance defined as p