Fulvestrant is commonly used in breast cancer patients, and the results vary from person to person with individual variability. This drug is mainly used in breast cancer patients who have failed endocrine therapy, and it is good to achieve therapeutic effect in female patients with recurrent or metastatic cancer as well as in cases where the cancer comes back after adjuvant anti-estrogen therapy. This drug is an anti-tumor targeting agent, which is mainly metabolized by the kidneys, but if the renal function impairment is more serious, the use of this drug needs to be cautious, so as not to cause aggravation of the disease. The use of this drug may lead to osteoporosis and endometrial thickening. Therefore, to assess the patient’s general condition, it is necessary to carry out relevant examinations, timely supplementation of calcium, gynecological ultrasound to assess the patient’s endometrial changes. If the endometrium has thickened significantly in the recent past, an endometrial biopsy is needed to determine whether the endometrium is cancerous or not. If cancer is present, early surgical treatment is needed.