Whether to give radiotherapy to breast cancer patients after surgery is usually based on the following principles: ① After minor surgery to preserve the breast, radiotherapy is mostly used to compensate for the lack of surgical scope. Doctors call this radical radiotherapy. ② For advanced cases, radiotherapy is often used to inhibit the development of cancer or to relieve the symptoms caused by metastases. It is called palliative radiotherapy. ③After radical mastectomy, if there is metastasis in the axillary lymph nodes (or metastasis to a certain extent), or if the tumor is located in the medial half of the breast and no extended radical surgery is performed, it is necessary to irradiate the axillary area, supraclavicular area, and internal breast lymphatic chain area alone or in combination. Doctors call it adjuvant radiotherapy.