This study focuses on individuals with early breast cancer that is ER+/HER2-. This means the cancer cells have receptors for estrogen (ER+) but do not have an excess of a specific protein called human epidermal growth factor receptor 2 (HER2-). The research aims to compare the effectiveness of a new treatment approach against the current standard of care to see which better prevents the cancer from returning or causing death.

Participants may receive elacestrant, which is a type of medication used to block the effects of hormones that help cancer grow. Some individuals might also be given ribociclib, a medication known as a CDK4/6 inhibitor that helps stop cancer cells from dividing. The treatments are administered as oral use tablets. Depending on the group assigned, some participants may receive these medications alone or in combination with other standard hormone therapies, and some may receive a placebo.

The study follows participants over a period of time to monitor how they respond to the different medication combinations. The process involves tracking long-term outcomes, such as overall survival, which is the length of time from the initial diagnosis until death, and disease-free survival, which measures the time during and after treatment that a person lives without any signs or symptoms of the cancer. The researchers will also look at how the treatments affect the quality of life and any side effects that may occur during the study period.