The goal of this clinical study is to see if sacituzumab govitecan-hziy (SG) can improve life
spans of people with HR+/HER2- metastatic breast cancer and their tumor does not grow or
spread when compared to current available standard treatments, such as paclitaxel,
nab-paclitaxel or capecitabine. The primary objective is to compare the effect of SG relative
to the treatment of physician's choice (TPC) on progression-free survival (PFS).

This phase II trial compares the effect of capecitabine to endocrine therapy in patients with non-Luminal A hormone receptor-positive breast cancer that has spread from where it first started (primary site) to other places in the body (metastatic). In this study, patients submit a sample of tumor for testing to determine if their breast cancer is considered non-Luminal A. Only patients with non-Luminal A receive study treatment. In the future, doctors hope that this test can assist in picking the best treatment for patients with this type of cancer. Capecitabine is in a class of medications called antimetabolites. It is taken up by tumor cells and breaks down into fluorouracil, a substance that kills tumor cells. Endocrine therapy is treatment that adds, blocks, or removes hormones. To slow or stop the growth of certain cancers (such as prostate and breast cancer), synthetic hormones or other drugs may be given to block the body's natural hormones. Giving capecitabine as compared to endocrine therapy may kill more tumor cells in patients with metastatic breast cancer.