Characteristics Of High Risk Breast Cancer Patients With Mutations Identified By Multiplex Panel Testing

1511 Background: Multiplex panel testing studies evaluating cancer susceptibility in breast cancer (BC) patients suggest that between 4-11% of BRCA1/2 negative individuals have a deleterious mutation in a high or moderate penetrance gene. The range in mutation positivity is likely due to heterogeneity of the studied patient populations. Methods: We performed targeted, massively parallel sequencing of 795 BRCA1/2 negative BC patients in a research laboratory and analyzed 18 cancer susceptibility genes.Three high risk groups were studied: multiple primary cancers (MP, n = 315), early onset breast cancer (EOBC, n = 323), and familial breast cancer (FBC, n = 415). MP was defined as at least one BC and at least one other primary malignancy excluding non-melanoma skin cancer, EOBC was defined as BC under age 40, and FBC was defined as at least three first to third degree relatives with BC under age 75. Results: Overall, 78 patients (10%) were found to have a deleterious mutation. Mutations were found most commo...