Level I-II Axillary Irradiation in Breast Cancer With Sentinel-Node Macro-metastases

Inclusion Criteria:

1. Female ≥ 18 years of age;
2. Newly diagnosed primary invasive breast cancer;
3. Clinically stage T1-3N0M0;
4. Patients received surgery as first treatment,and have undergone breast conserving-surgery or mastectomy (with or without breast reconstruction) with negative margins;
5. Have one or two macrometastases (\>2 mm) at sentinel lymph node biopsy,and without further axillary lymph node dissection;
6. Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1;
7. Will receive endocrine therapy for at least 5 years for estrogen receptor (ER) and/or progesterone receptor (PR) positive patients; will receive anti-HER2 (human epidermal growth factor receptor 2) therapy for 1 year for HER2 positive patients;
8. Radiation therapy must begin no later than 12 weeks after the last dose of adjuvant chemotherapy or the last breast cancer surgery if no adjuvant chemotherapy;
9. Patients have adequate organ function;
10. Acquirement of informed consent.

Exclusion Criteria:

1. Patients have received neoadjuvant systemic therapy;
2. Clinical stage T4 or IV (metastatic) breast cancer, or presence of regional metastases before surgery;
3. History of any prior ipsilateral or contralateral invasive breast cancer, history of other malignancies except for appropriately treated skin basal cell carcinoma and cervical carcinoma in situ;
4. History of previous radiotherapy towards the ipsilateral chest/lymph nodes.
5. The ipsilateral axillary lymph node dissection or other previous axillary surgery;
6. Current severe, uncontrolled systemic disease (e.g., clinically significant cardiovascular, pulmonary, hepatic, renal, hematologic, or psychiatric disease), inability to tolerate radiotherapy or systemic therapy if indicated;
7. Current pregnancy and/or lactation;
8. Inability or unwillingness to comply with protocol requirements.