Radiotherapy plays an important role in the comprehensive treatment of the breast. For early stage breast cancer, many clinical trials have demonstrated that breast-conserving surgery plus radiotherapy is as effective as modified radical surgery. With increasing diagnostic and therapeutic advances, patients with breast cancer usually achieve long-term survival; stage I and II breast cancers typically have 10-year survival rates of 95% and 88%, and the improvement in overall survival with radiation therapy has been partially offset by the cardiac damage it causes and other side effects during long-term follow-up. Cardiotoxicity caused by radiation therapy can be divided into short-term cardiotoxicity and long-term cardiotoxicity according to time, with long-term cardiotoxicity usually occurring several decades after radiation therapy. The evidence for ischemic disease in breast cancer radiotherapy comes from the EBCTCG meta-analysis of clinical trials in this organization. The most recent analysis showed that the relative risk of death from cardiac disease was higher in the group of patients who received radiotherapy after breast-conserving surgery compared with the group of patients who did not receive radiotherapy (RR=1.27; SE, 0.07; 2P_.0001). Since breast cancer irradiation, usually during left-sided chest radiotherapy and/or internal breast area radiotherapy, tends to irradiate part of the heart, the irradiation dose is usually not directly modulated during tangential irradiation or internal breast area irradiation, so reducing the volume of cardiac irradiation is a more studied approach.