Efficacy and Safety of Dalpiciclib With Endocrine Therapy as Adjuvant Treatment in HR+/ HER2- Early Breast Cancer

This study tests whether adding dalpiciclib (a drug that slows cancer cell growth by targeting specific proteins) to standard hormone therapy reduces the risk of early-stage breast cancer coming back in women with hormone receptor-positive, HER2-negative breast cancer. **You may be eligible if...** - You are 18 or older with a confirmed diagnosis of hormone receptor-positive, HER2-negative early breast cancer - Your cancer is stage IIA to IIIC - You have had surgery and your enrollment is within 12 months of the operation - Your general health status is good (ECOG 0 or 1) - You are pre-, peri-, or post-menopausal (menopausal status must be known) **You may NOT be eligible if...** - Your cancer has spread to other parts of the body (stage IV) or is inflammatory breast cancer - You have a history of another cancer (except certain cured skin or cervical cancers) - You have significant heart disease - You have a history of allergic reactions to the drugs in this study - You cannot swallow tablets - You have gastrointestinal disease with significant diarrhea Talk to your doctor to see if this trial is right for you.