Lung cancer is currently the most common malignancy worldwide, and with the increasing incidence of the disease, lung cancer has become the leading cause of cancer deaths, with approximately 2/3 of these patients already having distant metastases, or advanced lung cancer, at the time of diagnosis. Gefitinib is a potent epidermal growth factor receptor tyrosine kinase inhibitor that inhibits proliferation, growth, survival, and signaling pathways in advanced lung cancer patients with epidermal growth factor receptor-positive lung adenocarcinoma. It is usually taken once a day, one tablet at a time, on an empty stomach or with food. The most common adverse reactions to gefitinib are diarrhea, rash, itchy skin, dry skin, and acne, with an incidence of more than 20%, occurring within 1 month of taking the drug, and usually reversible. Currently, gefitinib is mainly indicated as first-line treatment for patients with advanced lung adenocarcinoma with epidermal growth factor receptor positivity.