A Study to Learn How Well Participants With a Specific Type of Early Breast Cancer (ER-Positive, HER2-Negative) Tolerate and Stay on Treatment With Giredestrant and How They Feel During Treatment

The purpose of this study is to evaluate treatment adherence, tolerability, and patient-reported outcomes of participants with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative early breast cancer (eBC) who are treated with giredestrant. The study will have two cohorts. Cohort A will comprise a broad upfront patient population with low-, medium-, or high-risk eBC. Cohort B will comprise patients with medium- or high-risk eBC who have completed adjuvant treatment with cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) (abemaciclib or ribociclib) and endocrine therapy and who are now switching to giredestrant monotherapy.