Tumor enlargement of lung cancer patients after three months of radiotherapy indicates that the disease is not under control and should be controlled by surgery or systemic therapy. Tumor enlargement after three months of radiotherapy for lung cancer usually indicates that the disease is not under control. If the patient’s physical condition allows, the diseased part can be removed by surgery and then treated with radiotherapy, chemotherapy and targeted drugs. If the patient’s physical condition is poor and cannot undergo surgery, or there are lymph nodes or distant metastases, he can be treated by radiotherapy and drugs, and the commonly used drugs are cisplatin, carboplatin, ositinib, afatinib and so on. Lung cancer patients whose tumors become bigger should go to hospital for treatment in time to avoid aggravation of the condition.