Localized Human Epidermal Growth Factor Receptor (HER2)-Negative Breast Carcinoma

This phase II trial studies how well imlunestrant and abemaciclib work in treating patients with estrogen receptor positive (ER+) breast cancer who have tumor remaining in the blood following treatment (minimal residual disease). Estrogen can cause the growth of breast cancer cells. Imlunestrant lowers the amount of estrogen made by the body. This may help stop the growth of tumor cells that need estrogen to grow. Abemaciclib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Imlunestrant and abemaciclib may be effective in treating patients with ER+ breast cancer who have minimal residual disease.