Abstract PS8-24: Clinical and pathologic characteristics of Turkish breast cancer (BC) patients screened with BRCA1, BRCA2 or 26 - gene inherited cancer panel testing: Single institution experience

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Abstract Background: BRCA1 and BRCA2 mutations are responsible for two thirds of hereditary BC. Germline genetic testing for BC susceptibility has evolved from a single-gene analysis to a multigene panel testing. Identification of a pathogenic mutation in BRCA and other panel represent a therapeutic opportunity today. Methods: We aimed to investigate clinical and pathologic characteristics of BC patients who were referred to our center between 2011-2019 and underwent BRCA1, BRCA2 or 26-gene inherited cancer panel testing based on NCCN criteria for hereditary breast/ovarian cancer testing. We analyzed the frequency of pathogenic mutations and its relationship with clinical and pathologic factors. Results: A total of 576 patients were identified. Among them 356 (63%) had their test in our university, 218 (38%) patients had their test at other centers. Sixty-six % (n:376) of patients had panel testing, 34% had only BRCA 1-2 mutation test. Median age was 42(22-87) and 5 patients were male. Ten % of patients had metastatic disease, 70% had early BC and 20% had locally advanced stage at the time of referral. The indication for genetic testing was family history in 169 (29%) patients, triple negative (TN) subtype in 100 (17%) patients and age <45 years in 260 (45%) patients. Seventy-nine % of patients were premenopausal. A total of 114 (19%) patients had pathogenic mutations. The most commonly mutated genes were BRCA1 (n:38, 6%), BRCA2 (n:35, 6%), ATM (n:6), p53 (n:5), PALB2 (n:5), CHEK2 (n:5). Six patients had more than one pathogenic mutation. Among patients with pathogenic mutations 58% had ER positive, 27% had TN and 15 % had Her-2 positive disease. Thirty-four % of patients with TN tumors have pathogenic mutations, 23% of patients with TN tumors had BRCA mutations. TP53, PALB2 and CHEK2 mutations were more frequent in HR positive disease. Age <35 (p:0.002), triple negative subtype (p: 0.005) and menopausal status (p:0.001) were significantly associated with having pathogenic mutations in multivariate analysis. Conclusion: Two thirds of BC patients <35 years-old and one third of patients with TN tumors have pathogenic germline mutations in BC predisposing genes when they were screened in line with NCCN criteria. Citation Format: Aysun Isiklar, Aykut Soyder, Kanay Yararbas, Cumhur Ekmekci, Hulya Yazici, Gul Basaran. Clinical and pathologic characteristics of Turkish breast cancer (BC) patients screened with BRCA1, BRCA2 or 26 - gene inherited cancer panel testing: Single institution experience [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS8-24.