Breast radiotherapy-related treatment outcomes in patients with or without germline mutations on multigene panel testing.

2021 
Purpose Multigene panel testing has increased the detection of germline mutations in patients with breast cancer. The implications of using radiotherapy (RT) to treat patients with pathogenic variant (PV) mutations are not well understood and have been studied mostly in women with only BRCA1 or BRCA2 PVs. We analyzed oncologic outcomes and toxicity after adjuvant RT in a contemporary, diverse cohort of breast cancer patients who underwent genetic panel testing. Methods and materials We retrospectively reviewed the records of 286 women with clinical stage I-III breast cancer diagnosed 1995-2017 who underwent surgery, breast or chest wall RT with or without regional nodal irradiation, multigene panel testing, and evaluation at a large cancer center's genetic screening program. We evaluated rates of overall survival (OS), locoregional recurrence (LRR), disease-specific death (DSD), and radiation-related toxicities in three groups: BRCA1/2 PV carriers, non-BRCA1/2 PV carriers, and patients without PV mutations. Results PVs were detected in 25.2% of the cohort (12.6% BRCA1/2 and 12.6% non-BRCA1/2). The most commonly detected non-BRCA1/2 mutated genes were ATM, CHEK2, PALB2, CDH1, TP53, and PTEN. The median follow-up time for the entire cohort was 4.4 years (95% confidence interval 3.8-4.9 years). No differences were found in OS, LRR, or DSD between groups (P>0.1 for all). Acute and late toxicities were comparable across groups. Conclusion Oncologic and toxicity outcomes after RT in women with PV germline mutations detected by multigene pane testing are similar to those in patients without detectable mutations, supporting the use of adjuvant RT as a standard of care when indicated.
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