Study Comparing Imlunestrant to Standard Hormone Therapy in Patients with Early Breast Cancer

Inclusion Criteria

• Diagnosed with early-stage breast cancer that is ER+ and HER2-, and has been surgically removed without spreading to other parts of the body.
• Have received hormone therapy for at least 2 years but not more than 5 years.
• May have had chemotherapy or targeted therapy with CDK4/6 or PARP inhibitors.
• Must have a higher risk of cancer returning based on certain clinical features.
• Have a good performance status, meaning fully active or restricted in physically strenuous activity but ambulatory.
• Have good organ function.

Exclusion Criteria

• Have any signs of cancer spreading or inflammatory breast cancer at the initial diagnosis.
• Have had a gap in hormone therapy longer than 6 months.
• Finished or stopped hormone therapy more than 6 months before the study screening.
• Have a history of breast cancer, except for a specific type treated over 5 years ago.
• Are pregnant, breastfeeding, or planning to have children during the study and for 180 days after the last dose.
• Have previously taken hormone therapy for breast cancer prevention.
• Have a history of any other cancer.
• Have serious medical conditions that would prevent participation in the study.