Expanded Gene Panel Use for Women With Breast Cancer: Identification and Intervention Beyond Breast Cancer Risk

Erin O’Leary, Daniela Iacoboni, Jennifer Holle, Scott T. Michalski, Edward D. Esplin, Shan Yang, Karen Ouyang

Clinicians ordering multi-gene next-generation sequencing panels for hereditary breast cancer risk have a variety of test panel options. Many panels include lesser known breast cancer genes or genes associated with other cancers. The authors hypothesized that using broader gene panels increases the identification of clinically significant findings, some relevant and others incidental to the testing indication. They examined clinician ordering patterns and compared the yield of pathogenic or likely pathogenic (P/LP) variants in non-BRCA genes of female breast cancer patients. This study analyzed de-identified personal and family histories in 1085 breast cancer cases with P/LP multi-gene panel findings in non-BRCA cancer genes and sorted them into three groups by the panel used for testing: group A (breast cancer genes only), group B (commonly assessed cancers: breast, gynecologic, and gastrointestinal), and group C (a more expanded set of tumors). The frequency of P/LP variants in genes with established management guidelines was compared and evaluated for consistency with personal and family histories. This study identified 1131 P/LP variants and compared variants in clinically actionable genes for breast and non-breast cancers. Overall, 91.5% of these variants were in genes with management guidelines. Nearly 12% were unrelated to personal or family history. Broader panels were used for 85.6% of our cohort (groups B and C). Although pathogenic variants in non-BRCA genes are reportedly rare, the study found that most were in clinically actionable genes. Expanded panel testing improved the identification of hereditary cancer risk. Small, breast-limited panels may miss clinically relevant findings in genes associated with other heritable cancers.