Germline Genetic Testing in Breast Cancer: Systemic Therapy Implications.

Approximately 5 to 10% of women diagnosed with breast cancer have a pathogenic variant in a hereditary cancer susceptibility gene, which has significant implications for managing these patients. Previously, testing was done mainly to inform screening and risk-reduction treatment; however, more recently, germline genetic results have significant systemic therapy implications that can meaningfully improve outcomes in breast cancer patients, especially with oral poly-ADP-ribose polymerase (PARP) inhibitors. These systemic therapy advances implore a shift in paradigm for whom to test moving forward and how to modify the existing testing models to meet the increasing demand for germline testing, which is expected to grow exponentially.