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