Some patients taking afatinib for a period of time will develop drug resistance, but not all. Regular review is recommended to determine whether drug resistance has occurred. Afatinib is clinically used for advanced or metastatic non-small cell lung cancer caused by mutations in the epidermal growth factor gene. A part of patients will develop drug resistance after using this product for a period of time, resulting in poorer efficacy and failure to control the disease. It is recommended to go to the hospital for regular review, and change the treatment strategy in time if drug resistance occurs, so as to avoid delaying the disease. The common adverse reactions of this product include diarrhea, rash, stomatitis, onychomycosis, etc. It is prohibited for patients who are allergic to this product. Please adhere to the doctor’s instructions to take medication and regular review, do not self-medication.