Impact of Omitting Chemo Based on Patient's Selection for ER-Positive, HER2-Negative Breast Cancer With Ribociclib and Endocrine Therapy

This study looks at whether certain breast cancer patients with hormone receptor-positive, HER2-negative cancer (the most common breast cancer type) can safely skip chemotherapy and do just as well with hormone-blocking therapy alone. Researchers are studying patients whose genomic tumor test results suggest a low risk of cancer returning. **You may be eligible if...** - You are 18 or older with ER-positive, HER2-negative breast cancer - You had breast-conserving surgery (lumpectomy) or a mastectomy with clear margins - You had a sentinel lymph node biopsy or axillary lymph node dissection - Your tumor characteristics (stage and gene expression score) suggest low risk of recurrence - You plan to take hormone-blocking therapy (such as tamoxifen or an aromatase inhibitor) for at least 5 years **You may NOT be eligible if...** - Your cancer has spread to distant parts of the body (stage IV) - You have an inflammatory breast cancer or a very large tumor (T4) - You have already received chemotherapy or targeted biologic therapy before surgery - You have taken hormone-blocking drugs in the past 2 years for cancer prevention Talk to your doctor to see if this trial is right for you.