Chemotherapy Omission in HR-positive/HER2-negative Breast Cancer With Lymph Node Negative Disease Receiving Adjuvant Endocrine Therapy and CDK4/6 Inhibitor

Exclusion Criteria

• •Bilateral breast cancer or carcinoma in situ (DCIS/LCIS);
• •Metastasis at any site;
• •Clinical or imaging suspicion of malignancy in the contralateral breast requiring biopsy (unless ruled out);
• •Prior neoadjuvant therapy, including chemotherapy, radiotherapy, or endocrine therapy;
• •Use of tamoxifen, raloxifene, or aromatase inhibitors (AIs) for breast cancer risk reduction ("chemoprevention") and/or osteoporosis treatment within the past 2 years;
• •History of other malignancies within the past 5 years (except basal cell carcinoma of the skin or carcinoma in situ of the cervix), including contralateral breast cancer;
• •Concurrent participation in another clinical trial;
• •Severe systemic diseases and/or uncontrolled infections that preclude study participation;
• •Severe cardiovascular or cerebrovascular events within 6 months before randomization (e.g., unstable angina, chronic heart failure, uncontrolled hypertension \>150/90 mmHg, myocardial infarction, or stroke);
• •Known hypersensitivity to the study drugs;
• •Men and women of childbearing potential unwilling to use contraception during treatment and for 8 weeks after treatment completion;
• •Pregnant or lactating women;
• •Positive pregnancy test before study drug administration (for women of childbearing potential);
• •Psychiatric disorders, cognitive impairment, or inability to comprehend the trial protocol, adverse effects, or comply with study procedures and follow-up (requires systematic evaluation before enrollment);
• •Individuals lacking personal freedom or legal capacity for independent civil conduct.