Increased Identification of Candidates for High-Risk Breast Cancer Screening Through Expanded Genetic Testing.

PURPOSE: Breast MRI screening is recommended for women with a >20% lifetime risk for breast cancer on the basis of estimates derived from risk models dependent largely on family history. Alternatively, a >20% lifetime risk can be established through genetic testing of BRCA1 and BRCA2, as well as a growing selection of other genes associated with inherited breast cancer risk. The aim of this study was to quantify the impact of testing for genes other than BRCA1/2 and the extent to which mutation carriers in these genes would have been identified as candidates for enhanced screening on the basis of family history alone. METHODS: Women were tested with a 25-gene hereditary cancer panel including BRCA1/2 and 7 additional genes known to be associated with a >20% lifetime risk for breast cancer (ATM, CHEK2, PALB2, TP53, PTEN, CDH1, and STK11). Women found to carry pathogenic variants (PVs) were evaluated with the Claus model to assess whether they would have been found to be at >20% lifetime risk on the basis of family history. RESULTS: In total, 9,751 PVs in the selected breast cancer risk genes were identified in 9,641 women. BRCA1/2 accounted for 59.1% of the PVs, and 38.8% were in ATM, CHEK2, or PALB2. Only 24.7% of all women with PVs found in any gene reached the >20% lifetime risk threshold using the Claus model. CONCLUSIONS: Expanding genetic testing beyond BRCA1/2 significantly increases the number of women who are candidates for breast MRI and other risk reduction measures, most of whom would not have been identified through family history assessment.