Radiation therapy for breast cancer is a major component of comprehensive treatment and is one of the local treatments. Currently, most scholars do not advocate radiation therapy alone for curable breast cancer. Radiation therapy for breast cancer is mostly used for comprehensive treatment, including adjuvant treatment before or after radical surgery, and palliative treatment for advanced breast cancer. In the past 10 years or so, there has been an increase in the number of local excision-based comprehensive treatment for earlier breast cancer, and the efficacy is not significantly different from radical surgery, and radiation therapy plays an important role in reducing the scope of surgery. The adjuvant radiotherapy after breast-conserving surgery for early stage patients Stage I and II breast cancer has a five-year local recurrence rate of 4.6%-6.1% after a combination of breast-conserving surgery and radiotherapy; the five-year survival rate is 78.8% -100%, and the cosmetically satisfactory and general results amount to about 92%, which is basically the same as the efficacy of modified radical surgery using mastectomy; while breast-conserving surgery without postoperative radiotherapy The recurrence rate of patients without postoperative radiotherapy was as high as 39% at 20 years of follow-up (NSABPB-06 trial), indicating the need for postoperative radiotherapy after breast-conserving surgery. The irradiation target area and dose: The site to be irradiated after breast-conserving surgery is the whole breast on the affected side, and the irradiation method is 6Mv-X-ray with a dose of 5000 cGy/25 times/5 weeks for the whole breast and then 1000 cGy/5 times/1 week for 12Mev electron beam at the primary tumor location in the surgical scar. For patients found to have cancer metastasis in ≥4 lymph nodes in the axilla, the supraclavicular region must also be irradiated at a dose of 5000 cGy/25 times/5 weeks. Adjuvant radiotherapy after modified radical surgery Some patients undergo modified radical surgery and have the affected breast removed. For patients after such surgery, radiation therapy must be administered in the following three cases: 1. The primary tumor of the breast is equal to or greater than 125px; 2. 4 or more lymph nodes with cancer metastasis are found; 3. Cancer clots are detected in the tumor invading the skin or blood vessels or lymphatic vessels. For patients without the above conditions, some of them can be considered for radiotherapy, and the doctors will decide whether to use radiotherapy according to the patients’ wishes after communicating with them. Adjuvant radiotherapy after modified radical surgery requires irradiation to the following sites: 1. skin of the affected chest wall: a common site of local recurrence after breast cancer surgery, and the literature reports that after local recurrence, many patients will subsequently develop distant hematologic metastases; 2. supraclavicular area: as recommended by the NCCN oncology treatment guidelines, strongly consider (4 lymph nodes) or consider (tumor larger than 3. Internal breast lymph nodes: Currently, due to the progression of chemotherapy drugs, internal breast lymph nodes are generally better controlled after regular chemotherapy, and radiotherapy can cause damage to the cardiovascular system, so if there is no evidence that cancer cells have metastasized to the internal breast lymph nodes, the NCCN oncology treatment guidelines only suggest that irradiation of them can be considered.