Abstract P2-09-08: Breast cancer tumor sequencing coupled with germline genetic testing aids the identification of at-risk individuals for hereditary breast cancer disorders

Abstract

Abstract Background: With the rise of precision medicine, hereditary cancer germline testing and tumor genetic testing have been increasingly used to inform the management of patients with cancer. Recent studies report that approximately 10% of patient’s tumors have clinically significant variants in genes known to predispose to a hereditary cancer syndrome. Here we report the concordance rate between tumor genetic testing and germline genetic testing in patients with breast cancer and review its impact on the patients’ management and implications for their relatives. Methods: In this study, we used de-identified data from 101 consecutive patients with breast cancer who underwent tumor genetic testing followed by germline testing with NGS-based hereditary cancer gene panels. Results: Tumor genetic testing results included likely pathogenic or pathogenic (LP/P) variants in BRCA2 (21%), BRCA1 (20%), TP53 (10%), CDH1 (7%), ATM (4.3%), PALB2,CHEK2, and PTEN (3.7% each), and PIK3CA (2.5%) among 22 other genes. In 33/101 cases (33%) the P/LP variant was also detected in the germline. Genes in which disease-causing variants were most frequently confirmed to be in the germline included: BRCA2 (36%), BRCA1(21%), PALB2 (12%), and CHEK2 (12%). Variants in ATM, FH, FANCA, and MSH6 were confirmed in the germline in <10% of patients with variants in these genes. Variants in the TP53, CDH1, and PIK3CA genes were detected in the tumor but not in the germline. In 1 case a pathogenic germline variant was detected in the BRIP1 gene but not reported in the tumor, because the gene was not included in the tumor testing panel. Conclusions: A significant proportion (33%) of patients with clinically significant variants in tumors were identified to carry the same variant in the germline, uncovering a previously unknown risk of hereditary breast cancer disorder. Notably, some genes had a high probability of variants occurring in the germline, while others were primarily seen in tumors. Performing simultaneous germline and tumor testing may inform susceptibility to a hereditary cancer disorder, identify targets for precision therapy, early detection of secondary malignancies, and guide genetic counseling for relatives. Citation Format: Daniel E Pineda-Alvarez, Scott T Michalski, Meaghan Russell, Shan Yang, Ihn Young Song, Robert L Nussbaum, Edward D. Esplin. Breast cancer tumor sequencing coupled with germline genetic testing aids the identification of at-risk individuals for hereditary breast cancer disorders [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-09-08.