A Study of Postoperative Regional Nodal Radiotherapy in Intermediate-risk Breast Cancer

Inclusion Criteria: * Female patients aged 18 or above * Undergo breast-conserving surgery or total mastectomy and axillary lymph node dissection or sentinel lymph node biopsy * The surgical margin was negative * Tumor stage:Patients who receive direct surgery : pT1-2N1M0, with at least one lymph node having macrometastasis and a tumor risk score of 0-2.For those who underwent surgery after neoadjuvant chemotherapy: cT1-2N1-2M0→ypT0-2N0M0 (cN+ with pathological confirmation), neoadjuvant Chemotherapy for ≥6 cycles. Exclusion Criteria: * distant metastasis * metastasis of ipsilateral internal mammary, supraclavicular or subclavian lymph nodes * Had received chest radiotherapy in the past * Bilateral breast cancer * Pregnancy or lactation period * Other malignant tumors in the past or at the same time, and the tumor-free survival time is less than 5 years (excluding non-malignant melanoma skin cancer, papillary thyroid carcinoma/follicular carcinoma, cervical carcinoma in situ)