1.Small cell lung cancer is more malignant and sensitive to radiotherapy and chemotherapy. 2.The survival period of most patients with chemotherapy alone is about 10 months-12 months. 3.The main reason for treatment failure is local recurrence after treatment, followed by rapid multi-organ and multi-site metastasis. Therefore, controlling local recurrence and improving local control rate can achieve the purpose of prolonging tumor-free survival time of patients and slowing down metastasis. 4. Concurrent radiotherapy can greatly improve the local control rate, and the 5-year survival rate can sometimes reach more than 30%. At the same time, systemic treatment can slow down distant metastasis, and the combined effects of radiotherapy and chemotherapy do not delay the treatment time, thus improving the tumor control rate and survival rate as a whole. Treatment principles of small cell lung cancer 1. The National Cancer Multi-Cooperative Treatment Group recommends that concurrent radiotherapy is the standard treatment plan for small cell lung cancer. 2. 2 cycles of EP program are given during radiotherapy, and 3-4 cycles of chemotherapy are given after radiotherapy according to the disease and physical condition. The chemotherapy regimen can also be a second-line regimen of platinum combined with pemetrexed. 3.If physical or other conditions do not allow, local radiotherapy should also be given to the tumor as early as possible. 4.After lung radiotherapy is finished, the patient and family can choose or not to choose brain prophylaxis according to their wishes.