2. Histologically proven diagnosis of breast cancer with evidence of metastatic disease or locoregional recurrence. 3. Histological confirmation and documentation of estrogen receptor (ER)-positive status (≥1% positive stained cells). 4. Histological or cytological confirmation and documentation of human epidermal growth factor receptor-2 (HER2)-negative status by local laboratory testing using criteria in the American Society of Oncology (ASCO)/College of American Pathologists (CAP) Clinical Practice Guideline update.