The treatment course of letrozole for breast cancer patients is at least five years, letrozole is an aromatase inhibitor, this treatment belongs to the endocrine treatment of breast cancer, which is an important treatment for breast cancer, and is also a systemic treatment. Endocrine therapy has the characteristics and advantages of low side effects and precise efficacy, but also has the characteristics of slow onset and long duration of treatment. In the process of taking the drugs, it is important to pay attention to the side effects and side effects of the drugs, such as osteoporosis and dyslipidemia, etc. Also, during the period of taking the drugs, patients with breast cancer still need to be reviewed regularly to observe whether there is any local recurrence or metastasis, so as to observe whether it is necessary to change the drug treatment.