Clinical Study on Adjuvant Therapy of TQB3616 Combined With Endocrine Therapy Compared With Placebo Combined With Endocrine Therapy in Patients With Breast Cancer

This trial tests whether adding a CDK4/6 inhibitor (TQB3616) to standard hormone therapy helps prevent breast cancer from returning in women with HR-positive, HER2-negative breast cancer after surgery. **You may be eligible if...** - You are 18–75 years old with HR-positive, HER2-negative invasive breast cancer - You have had a radical mastectomy - Your blood counts and organ function meet the required levels - Your heart pumping function (LVEF) is 50% or higher **You may NOT be eligible if...** - You have had another malignancy - You have significant heart, liver, or kidney problems - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.