A Randomized, Phase II Trial of Circulating Tumor DNA-guided Second Line Adjuvant Therapy for High Residual Risk, Estrogen Receptor Positive, HER-2 Negative Breast Cancer (DARE)

Surveillance population and ctDNA screening (up to 1000 patients): High risk ER positive, HER2-, breast cancer patients who have completed adjuvant endocrine therapy, or are currently receiving adjuvant endocrine therapy with an aromatase inhibitor or tamoxifen and are within 7 years since completion of definitive breast surgery are eligible for ctDNA screening. In order to start ctDNA surveillance, patients must have completed at least 6 months, but no more than 7 years of adjuvant endocrine therapy of treatment without distant recurrence. Prior adjuvant CDK4/6 therapy is allowed, but at lea…