The research hypothesis is that the tumor-free survival rate of intermediate-risk breast cancer patients exempted from RNI is not inferior to that of those receiving RNI. Patients with intermediate-risk breast cancer have a relatively low local-regional recurrence rate whether they undergo RNI or not.Patients were randomly assigned to the RNI group and the non-RNI group.After radiotherapy,the patients are followed the efficacy and toxicities of radiotherapy are evaluated.

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)