Postmastecomy Internal Mammary Nodal Irradiation for High-risk Breast Cancer Patients

Inclusion Criteria: * Eastern Cooperative Oncology Group Performance Status Scale 0-2 * Histologically confirmed invasive breast cancer * Underwent total mastectomy/breast-conserving surgery and axillary dissection(10 or more axillary lymph nodes detected) and negative margins * Patients who had ≥4 positive axillary lymph nodes; or 1-3positive axillary lymph nodes and T3-4; or 1-3positive axillary lymph nodes and T1-2, and score≥3 based on the following high risk factors: age≤40 years(score 1), primary tumor in the inner quadrant (score 1), 2-3 positive axillary lymph nodes (score 1), positive vascular invasion (score 1), re-staged based on eighth Cancer Staging System staging system(IB-IIA score 1， IIB-IIIA score 2); or ypN+ after neoadjuvant chemotherapy * No supraclavicular or internal mammary nodes metastases based on images before system therapy * No distant metastases * Could tolerate radiotherapy * Treated with chemotherapy (anthracycline and/or taxane-based combined chemotherapy, ≥6 cycles) * Anticipated to receive endocrine therapy for 5 years if indicated * Anticipated to receive anti-HER2 therapy for 1 years if indicated * LVEF≥50% based on echocardiogram * Willing to follow up * Written,informed consent Exclusion Criteria: * Simultaneous bilateral breast cancer * Sentinel lymph node biopsy only without axillary dissection * Had received internal mammary node dissection * No imaging assessment of the internal mammary nodal before system therapy * One-stage breast reconstruction * Severe cardiac insufficiency; myocardial infarction or uncorrected unstable arrhythmia or uncorrected unstable angina in the last 3 months; pericardial disease * Had history of chest wall or supraclavicular radiotherapy * Had simultaneous or previous secondary malignancies, except for non-malignant melanoma skin cancer, papillary thyroid / follicular carcinoma, cervical carcinoma in situ, contralateral non-invasive breast cancer