This study compares **imlunestrant**, a new drug, to standard hormone therapy for people with early breast cancer that is **estrogen receptor positive (ER+)** and **human epidermal receptor 2 negative (HER2-)**. ER+ means the cancer cells grow in response to estrogen, a hormone, while HER2- indicates they do not have too much of a protein called HER2. To join, participants must have taken hormone therapy for 2-5 years and have a higher risk of cancer returning. The study might last up to 10 years.

Key Points:

• Study duration can be up to 10 years.
• Participants might have taken hormone therapy for 2-5 years before joining.
• Eligibility includes having a higher risk of cancer returning.

If you have had metastatic disease, gaps in hormone therapy, or other types of cancer, you may not be eligible. Pregnant or breastfeeding people are also excluded. It's important to discuss with your doctor if this study is a good fit for you.