LAUSR

INTRODUCTION The use of restricted versus expanded panel genetic testing in breast cancer is controversial, with some institutions offering predominantly abbreviated gene panel testing. Our community program has offered larger panel testing for several years. We sought to evaluate the outcomes of large panel genetic testing and understand their impact on patient care. METHODS A retrospective review of our multi-institutional tumor registry was performed from 2015 to 2018 for patients undergoing surgery for breast cancer. Referral to genetic counseling and outcomes of panel testing were examined. RESULTS 2237 patients met study criteria. Median age was 63 years (range 22-99). Eight hundred and thirty-eight patients (37.4%) were referred for genetic counseling. Of these patients, 509 (60.7%) had negative results, 108 (12.8%) had deleterious mutations (37 not included in abbreviated panels), and 221 (26.3%) had variants of undetermined significance (VUS). Bilateral mastectomy rates for patients with deleterious mutations were 53.7%, versus 31% for negative and 32.6% for VUS. DISCUSSION Large panel testing finds a significant number of actionable mutations. The increased identification of VUS did not result in higher mastectomy rates.