Axillary Radiotherapy for Early Stage Breast Cancer With Limited Positive Sentinel Lymph Nodes

Inclusion Criteria: * Female * 18\~70 years old * Pathologically confirmed invasive breast cancer * A clinical T1-2N0M0 tumor * Treated with breast conserving surgery and sentinel lymph node biopsy * 1\~2 positive sentinel lymph nodes, including micro-metastases or macro-metastases. * ECOG score 1\~2 * Written informed consent Exclusion Criteria: * Patients underwent complete axillary lymph node dissection * Patients underwent mastectomy * Patients underwent neoadjuvant therapy * Clinically node positive pre-operative * Sentinel lymph nodes only containing isolated tumour cells (\<0.2 mm) * Prior history of invasive breast cancer or previous or concurrent other malignancies within the past 5 years * Previous radiation therapy of breast or thorax * Medical contraindication for radiotherapy * Prior axillary surgery or radiotherapy * Unable or unwilling to receive breast conserving surgery or sentinel lymph node biopsy * Pregnant or nursing