How breast cancer returns in patients taking cell cycle inhibitors

This is a real-world research study that follows patients who have been diagnosed with early-stage, hormone-sensitive breast cancer and are being treated with either abemaciclib or ribociclib — medications designed to help prevent cancer from coming back. Researchers want to understand what happens in patients whose cancer does return while taking this medication, including how often it happens, where it comes back, and what treatment options work best next.

These medications are relatively newer treatments for breast cancer, and doctors need to better understand how patients respond to them in everyday practice — not just in controlled clinical trials. By studying real patients and their outcomes, researchers can identify patterns and improve how to care for people whose cancer returns despite this medication.