Small cell lung cancer accounts for 15% of lung cancer incidence, and most (approximately 98%) are associated with smoking. It is clinically classified into limited and extensive stages based on the extent of invasion. Limited stage: The lesion is located in one hemithorax and can be safely encircled by a radiation field. Less than 5% of patients can be treated surgically and the rest are given concurrent chemotherapy + radiotherapy, except for those without lymph node metastases, which require chemotherapy alone. Chemotherapy regimen: cisplatin + etoposide, or carboplatin if cisplatin is not tolerated. Radiotherapy is started in the first or second cycle; the dose can be 1.5 Gy/dose twice a day, accumulating 45 Gy; 1.8-2.0 Gy/dose once a day, accumulating 60-70 Gy. Extensive stage: lesions beyond one half of the chest cavity, including malignant pleural or pericardial effusion or blood metastases. If combined with local symptoms, such as superior vena cava compression sign, pulmonary infarction, bone metastasis, spinal cord compression sign, chemotherapy +/_ radiotherapy should be given. Patients with brain metastases are given radiotherapy + chemotherapy if they have brain symptoms; otherwise, chemotherapy is given before radiotherapy. Chemotherapy regimen: cisplatin + etoposide, carboplatin + etoposide, cisplatin + irinotecan, carboplatin + irinotecan, cyclophosphamide + adriamycin + vincristine. Patients with recurrent metastases within 2-3 months and in good health can be treated with cyclophosphamide, paclitaxel, gemcitabine, irinotecan, topotecan. within 3-6 months, topotecan, irinotecan, cyclophosphamide + adriamycin + vincristine, gemcitabine, paclitaxel, oral etoposide, vincristine. above 6 months, the original regimen can be applied.