Multigene Panel Testing Detects Equal Rates of Pathogenic BRCA1/2 Mutations and has a Higher Diagnostic Yield Compared to Limited BRCA1/2 Analysis Alone in Patients at Risk for Hereditary Breast Cancer

Background. Recently introduced multigene panel testing including BRCA1 and BRCA2 genes for hereditary cancer risk has raised concerns with the ability to detect all deleterious BRCA1/2 mutations compared to older methods of sequentially testing BRCA1/2 separately. The purpose of this study was to evaluate rates of pathogenic BRCA1/2 mutations and variants of uncertain significance (VUS) between previous restricted algorithms of genetic testing and newer approaches of multigene testing. Methods. Data was collected retrospectively from 966 patients who underwent genetic testing at one of three sites from a single institution. Test results were compared between patients who underwent BRCA1/2 testing only (limited group, n = 629) to those who underwent multigene testing with 5-43 cancer-related genes (panel group, n = 337). Results. Deleterious BRCA1/2 mutations were identified in 37 patients, with equivalent rates between limited and panel groups (4.0 vs. 3.6 %, respectively, p = 0.86). Thirty-nine patients had a BRCA1/2 VUS, with similar rates between limited and panel groups (4.5 vs. 3.3 %, respectively, p = 0.49). On multivariate analysis, there was no difference in detection of either BRCA1/2 mutations or VUS between both groups. Of patients undergoing panel testing, an additional 3.9 % (n = 13) had non-BRCA pathogenic mutations and 13.4 % (n = 45) had non-BRCA VUSs. Mutations in PALB2, CHEK2, and ATM were the most common non-BRCA mutations identified. Conclusions. Multigene panel testing detects pathogenic BRCA1/2 mutations at equivalent rates as limited testing and increases the diagnostic yield. Panel testing increases the VUS rate, mainly as a result of non-BRCA genes. Patients at risk for hereditary breast cancer can safely benefit from up-front, more efficient, multigene panel testing.