Small cell lung cancer accounts for 15% of all lung cancers and approximately 98% of small cell lung cancers are associated with smoking. Others are associated with environmental and genetic factors. Clinical manifestations Cough, dyspnea, weight loss and debility with or without obstructive pneumonia, which are often caused by larger masses at the hilum and enlarged mediastinal lymph nodes. Neurological and endocrine paraneoplastic syndromes caused by the tumor include Lan-I syndrome, cancer-related encephalomyelitis and sensory neuropathy, as well as Cushing’s syndrome and hyponatremia. Prognostic factors Poor body mass, extensive stage, weight loss, multiple sites of tumor invasion and tumor overgrowth are important poor prognostic factors. In the limited stage, women, under 70 years old, stage I, and normal LDH have better prognosis; in the extensive stage, those with normal LDH and single metastases have good prognosis, and the number of involved organs is negatively correlated with prognosis, and the prognosis of liver metastases is worse. Those with endocrine paraneoplastic syndrome have a poorer prognosis. Examination methods Physical examination, chest X-ray, chest and abdomen CT, head MRI, bone scan. PET scan if necessary. About 30% of patients with normal or asymptomatic alkaline phosphatase levels have positive bone scans; about 10% to 15% of newly diagnosed patients have central nervous system metastases detected by cranial CT or MRI scans, and 30% of them are asymptomatic. Due to the rapid growth of small cell tumors, most patients develop typical symptoms within 8 weeks, and later the disease progresses significantly faster, so do not delay treatment by spending too much time on examination and staging. Chemotherapy and radiotherapy are the main treatments for small cell lung cancer. For patients with limited stage, simultaneous chemoradiotherapy is recommended, with 4 cycles of chemotherapy with a platinum/pediposide based regimen and chest radiotherapy should be started in the 1st or 2nd cycle at a dose of 1.8 Gy per day or higher (total dose of 45 Gy). PCI is recommended for those who have complete disappearance or significant reduction of tumor after treatment, and some patients with limited stage can be cured by standardized chemoradiotherapy. Only 2% to 5% of the earlier stage tumors are suitable for surgical resection, but chemotherapy and chemoradiotherapy are still required after surgery. Almost all small cell lung cancers will eventually progress to the extensive stage. For patients with extensive stage, adequate chemotherapy with standard combination regimens is recommended. Those with recurrent tumors may have palliative radiotherapy or palliative chemotherapy to relieve pain, reduce symptoms, and improve quality of life, as well as laser therapy, internal radiation therapy, or stent placement to relieve symptoms. Continued smoking increases toxicity and has a short survival period, so patients should be encouraged to quit smoking. Follow-up visits are recommended every 2-3 months for the 1st to 3rd year after the end of treatment for physical examination and imaging of the chest and symptomatic areas. Chemotherapy (abbreviated as chemotherapy) Chemotherapy is an important part of the treatment of small cell lung cancer. Simultaneous chemoradiotherapy in the limited stage, even with complete surgical resection, should be given in adequate amounts as adjuvant chemotherapy after surgery. Most patients have advanced to the extensive stage by the time they are seen, making combination chemotherapy the most basic form of treatment. The chemotherapy regimen for the limited stage is “cisplatin + etoposide, carboplatin + etoposide”, and the overall efficiency of chemotherapy combined with radiotherapy or combination chemotherapy for the limited stage is 70-90%, of which 50-70% achieve complete remission; the chemotherapy regimen for the extensive stage is “cisplatin + etoposide, carboplatin + etoposide, cisplatin + irinotecan”. Cisplatin + irinotecan”, the total efficiency is 60-70%, of which 8-30% achieve complete remission, the median remission period is about 6-8 months. Optional drugs after relapse are: isocyclophosphamide, paclitaxel, docetaxel, gemcitabine, irinotecan, vincristine, etc. Chemotherapy is effective in 75% to 90% of patients with limited stage, and about 50% of tumors disappear completely. The common side effects of chemotherapy include loss of appetite, nausea, vomiting, mouth ulcers, hair loss, reduction of white blood cells and platelets, etc., but they can be controlled and gradually return to normal with appropriate treatment. Don’t give up chemotherapy easily because of these temporary side effects, the benefits of reasonable chemotherapy far outweigh the disadvantages. Radiation therapy Chest radiotherapy: In patients with limited stage, the local control rate can be increased by 25%-30% with the combination of chest radiotherapy on the basis of chemotherapy, and the 2-year survival rate can be increased by 5%-7%. Early radiotherapy has longer survival than delayed radiotherapy, and synchronized radiotherapy to the chest is better than sequential radiotherapy. Early addition of radiotherapy not only improves the local and systemic disease control rate, but also prolongs survival. Prophylactic cranial irradiation (PCI): The incidence of brain metastasis is 80% in patients with small cell lung cancer who survive for 2 years, so it is feasible to prevent brain metastasis with prophylactic radiotherapy to the brain after satisfactory control of lung lesions in small cell lung cancer, and PCI can prevent the occurrence of brain metastasis in some patients. At present, international authorities recommend that whole brain prophylactic irradiation should be given to those with complete disappearance of tumor or less than 10% of residual tumor after treatment in limited or extensive stage (not recommended for those with many complications, poor general condition or mental and psychological incompetence). The recommended dose of irradiation is 24 Gy (in 8 fractions) to 36 Gy (in 18 fractions), and low-dose fractionated radiotherapy (1.8-2 Gy/dose) is recommended. Cephalic irradiation should not be administered simultaneously with systemic chemotherapy to avoid aggravating neurotoxicity.