Radiotherapy is required for breast cancer with metastasis in 1 lymph node in the axilla if breast-conserving surgery is performed, and for total mastectomy based on axillary management and tumor stage. Radiotherapy is required for breast-conserving mastectomy to remove possible residual local tumor cells. For total mastectomy with axillary lymph node dissection, radiotherapy is recommended for T3-4 (tumor lesions >5 cm or invading the skin or chest wall), and can be considered for T1-2 (tumor ≤5 cm). If axillary lymph node dissection is not performed, radiotherapy can be considered for the presence of 1 lymph node micro-metastasis confirmed by sentinel lymph node biopsy, and radiotherapy is recommended for the presence of 1 lymph node macro-metastasis. Whether or not to carry out radiotherapy needs to take into account the local condition, general physical condition and the patient’s wishes, etc. It is recommended that the patient should consult a specialist in time to choose the appropriate treatment.