Elacestrant versus Standard Endocrine Therapy in Women and Men with Node-positive, Estrogen Receptor-positive, HER2-negative, Early Breast Cancer with High Risk of Recurrence - A Global, Multicenter, Randomized, Open-label Phase 3 Study (ELEGANT)

The Sponsor has developed the study medication, elacestrant. Elacestrant is approved for treatment of participants with ER+/HER2- locally advanced or metastatic breast cancer with activating ESR1 mutation in the European Union and the United Kingdom.This study will look at elacestrant in the early breast cancer setting, among patients who received prior standard of care (SoC) endocrine therapy and have a high risk of the breast cancer coming back as determined by their doctor.Elacestrant will be taken daily by mouth in 86 mg or 345 mg tablets doses. The starting dose of elacestrant is 345 mg. Elacestrant or the SoC will be given in cycles. Each cycle lasts 28 days. The treatment duration is 5 years. It will take a maximum of 8 years to complete this research study, including the safety follow-up and the long-term follow-up. Participants will be assigned by chance to either switch to elacestrant or continue their current endocrine therapy that is considered SoC. The SoC medications that will be used in this study include anastrozole 1 mg daily, letrozole 2.5 mg daily, exemestane 25 mg daily, or tamoxifen 20 mg daily.Patients may be invited to take part in this study if they have been diagnosed with ER+, HER2- early breast cancer with high risk of coming back.This study will be carried out at multiple locations in North America, South America, Europe, Middle East, Asia and Oceania for a total of approximately 30 countries. Approximately 4220 study participants are expected to take part in this study.During the study, participants will undergo study related tests and procedures such as (but not limited to) physical examinations, blood and urine samples, electrocardiograms and tumour assessments.