BRCA1/2 mutation prevalence among triple-negative breast cancer patients from a large commercial testing cohort.

1544 Background: BRCA1/2 deleterious mutation identification among triple-negative breast cancer (TNBC) patients has gained importance due to cancer-risk management implications for patients and their relatives, and also has an emerging role in guiding treatment selection for therapies such as PARP inhibitors. The National Comprehensive Cancer Network (NCCN) currently recommends BRCA1/2 testing for TNBC patients diagnosed at age <60. Mutation prevalence among TNBC patients has previously been studied only in small regionalized cohorts. A recent study in unselected patients using the updated definitive criteria for TNBC reported mutation prevalence as 10.6%. Methods: Following the 2011 NCCN Hereditary Breast and Ovarian Cancer (HBOC) Testing Criteria update, serial cohorts of > 5,000 Ashkenazi Jewish and > 65,000 non-Ashkenazi Jewish breast cancer patients undergoing commercial BRCA1/2 testing were analyzed. Age at diagnosis, ethnicity, and provider-reported TN status were obtained from test requisition forms completed by ordering providers, and correlated with test results. Neither the accuracy nor definitive criteria used for TN status reported was independently verified. Results: Incidence of TNBC was reported as 9.7% among non-Ashkenazi patients and 16.5% within the subset with African ancestry. Incidence of TNBC was reported as 4.5% among Ashkenazi patients, but this is likely affected by test ordering for this population. The Table displays the BRCA1/2mutation rates classified by ethnicity and age-group. Conclusions: This study provides the most robust estimate to date of BRCA1/2 mutation prevalence among TNBC patients of all ages. The mutation rates seen among TNBC patients diagnosed after age 60 also illustrate the importance of testing such patients who may not meet the current NCCN HBOC testing criteria. [Table: see text]