To further improve outcomes and reduce unnecessary treatment for breast cancer patients, Exact Sciences is developing a genomic test designed to evaluate the activity of 16 cancer genes with the goal of determining benefit from radiation therapy after breast-conserving surgery. The gene expression signature developed by PFS Genomics, a company Exact Sciences acquired in early 2021, addresses a major clinical need: identifying which women with early-stage breast cancer need radiotherapy and which do not. Being able to provide women with a clear answer to this question has the potential to minimize over- or under-treatment and allow women to further personalize their breast cancer treatment plans.