Genetic Variation and the Role of Multigene Panel Testing for Hereditary Breast Cancer: A Single-Institution Experience.

Background Breast cancer is the second leading cause of cancer death in women. There are multiple pathogenic mutations in addition to BRCA1/2 that are implicated in causing hereditary breast cancer. Methods and results We conducted a retrospective analysis of 1568 patients with breast cancer diagnosed between January 1, 2015, and December 31, 2018. The age range is 23-87. Among the study population, 26% had genetic testing and 8% of those were found to carry a pathogenic variant, as designated in NCCN (National Comprehensive Cancer Network) Guidelines. Of that 8%, 3.4% were BRCA1 and BRCA2 mutations, and the rest were other prevalent pathogenic variants. Discussion Expanded panel testing has the potential to increase the detection rate of pathogenic variants compared to testing for BRCA1/2 alone. Diagnostic accuracy of genetic causes of breast cancer has a significant clinical impact on patients and their families in terms of targeted treatment and prevention strategies. There is a strong need for further understanding of genetic patterns and variations in hereditary breast cancer. Awareness of the possibility of moderate to low penetrance genes and variants of uncertain significance (VUS) is important to assist with appropriate genetic counseling. We believe that physicians should consider re-testing with an expanded panel if patients previously had BRCA1 and BRCA2 testings only with a negative result as it may identify additional mutations.