Radiotherapy is widely used in breast cancer. Radiotherapy is a kind of local treatment, and its application in breast cancer is specifically reflected in the following aspects: 1. Radiotherapy after breast-conserving surgery: after breast-conserving surgery, the whole breast is preserved, and radiotherapy after surgery is definitely indispensable; 2. After mastectomy: this part of patients in the middle to late stage; 3. Patients with local or regional recurrence of breast cancer, such as after breast cancer surgery, the chest wall has grown another If a lump grows out of the chest wall or a lump grows out of the neck, radiotherapy needs to be added again for intervention; 4. Treatment of breast cancer metastases, such as breast cancer with bone metastases, causing pain and needing radiotherapy for pain relief, or breast cancer with vertebral metastases, compressing the spinal cord, which may cause the risk of paraplegia requiring radiotherapy. Or breast cancer, which may cause pathological fracture, also needs radiotherapy intervention; 5. The more common metastatic site of breast cancer is brain metastasis, which also needs radiotherapy when brain metastasis, and the drugs can rarely enter the skull, which also needs radiotherapy intervention to relieve the patient’s symptoms and improve the patient’s quality of life.