There is no research data to show how long to take exemestane will develop drug resistance, the disease is different, the treatment cycle is also different. Exemestane can be used for the adjuvant treatment of early invasive breast cancer in postmenopausal estrogen receptor-positive women after 2-3 years of adjuvant treatment with tamoxifen, one needs to complete 5 years of adjuvant endocrine therapy, there are no studies on drug resistance. Exemestane use may appear after hot flashes, joint pain, insomnia, increased sweating, increased appetite, urticaria, hepatitis and other adverse reactions, allergic to the components of this product, premenopausal, pregnancy, lactation and other patients are prohibited, athletes, patients with hepatic and renal impairment, etc. Use with caution. It is recommended that patients go to the hospital in a timely manner, and strictly follow the medical advice to use medication.