Abstract ES2-3: Managing increased breast cancer risk based on high and moderate penetrance gene mutations

Abstract Genetic testing in the modern era increasingly examines multiple genes using next generation technologies. Most assays include the high penetrance genes, which confer lifetime breast cancer risk greater than 5-fold, include BRCA1/2, TP53, CDH1 and PALB2. Moderate penetrance genes are associated with lifetime breast cancer risk in the range of 2-3 fold, and include ATM, NF1, CHEK2 (mutation-specific) and NBN, with BARD1 and others potentially joining the group. Substantial data has emerged from studies of women with BRCA1/2 mutations, evaluating the performance of screening technologies, such as mammogram, breast MRI and ultrasound, and the efficacy of risk-reducing breast and ovarian/fallopian tube surgical procedures. Guidelines exist in the NCCN (US) and ESMO guidelines in Europe, among others, trying to provide recommendations for the age at which to initiate screening or undergo risk-reducing salpingo-oophorectomies, for example. Data are increasing on the moderate penetrance genes but there is still much reliance on extrapolation from the high-penetrance genes, which should be done thoughtfully. One approach is to estimate the age at which lifetime breast cancer risk equals the risk from a high penetrance gene when screening is to begin and initiate imaging surveillance at that time. For example, initiation of annual breast imaging would be at age 40 for ATM (RR 2.8) instead of age 25 as is done for BRCA1/2 or age 20 as for TP53. However, there are no data that this is the correct age at which to initiate screening, so this practical suggestion must meet criteria for reasonableness as well as effectiveness. Other source of data may include more precise gene-specific risk estimates from focused genetic epidemiology studies, and ongoing data from studies of prospectively identified mutation carriers. Further understanding of the mechanisms of carcinogenicity for mutation carriers may also help to provide insights that can guide therapeutic and preventive approaches. For example, the work on RANK ligand by Lindeman et al has led to the development of a definitive breast cancer prevention trial examining the RANK-Ligand inhibitor Denosumab in BRCA1 mutation carriers, entitled BRCA-P, being led by C. Singer of the ABCSG and Dr. Lindeman, and to be conducted in sites around the world. Other approaches are in development and will be discussed. Citation Format: Garber JE. Managing increased breast cancer risk based on high and moderate penetrance gene mutations [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr ES2-3.