There are indications for the use of endocrine therapy after breast cancer surgery, and it is not used casually, because the pathology of breast cancer has to be done after resection and the patient has immunohistochemistry. This treatment is ineffective because the content of estrogen receptor is relatively high in cancer cells, which we call hormone-dependent tumor. the purpose of treatment. However, in recent years, there are some better drugs, which we call aromatase inhibitors, such as letrozole, which achieve this therapeutic effect. Whether this treatment can be used or not is determined by the immunohistochemical results of the postoperative pathology, so it is not used casually, and generally after surgery, it should be combined with radiotherapy, and if conditions are suitable, endocrine therapy can be continued to achieve better long-term results.