ERSA, also known as Gefitinib, is an imported targeted drug for the treatment of lung cancer, mainly used for patients with positive epidermal growth factor receptor, and costs around RMB 2200 per box of 30 tablets. Gefitinib is mainly an oral treatment, usually 1 tablet per time, once a day, which is 250mg, taken on an empty stomach or with food, without dose adjustment according to the patient’s age, weight, gender, kidney function status, and moderate or severe liver insufficiency due to tumor liver metastasis. The incidence of adverse drug reactions, such as diarrhea, rash, itching, dry skin and acne, is over 20% and is seen within 1 month of taking the drug and is usually reversible.