Small cell lung cancer tumors enlarged by 1 cm should be treated with chemotherapy, radiotherapy, fusion therapy or immunotherapy. Small cell lung cancer tumors are one of many types of lung cancer and are malignant tumors that grow at a rapid rate. The main focus is usually on the use of moderately intensive chemotherapy, the efficacy of which is seen within 1-2 weeks after treatment. The use of effective chemotherapeutic agents to form a combination chemotherapy regimen is more effective than single-agent chemotherapy. Radiation therapy and chemotherapy are usually treated in tandem, and patients must be under the guidance of their doctors and actively cooperate with the treatment in order to control the progression of the disease. If the lung tumor is relatively large and produces serious damage to the lungs, radiotherapy can be chosen to control the condition when chemotherapy treatment is available, which can avoid the harm of spreading and metastasis of malignant tumors. For small cell lung cancer tumor enlargement can also be treated by local ablation therapy, giving targeted therapy to the place with disease, inhibiting endothelial growth of blood vessels, and enhancing the immunity of the body. Immunotherapy is a kind of treatment that applies doxorubicin and atilizumab, utilizing PD-1 and PD-L1 inhibitory points to make them pair with tumor cells, thus activating autoimmune cells to kill tumor cells. At present, the treatment of small cell lung cancer mostly adopts combined immunotherapy after radiotherapy and chemotherapy, and the effect is more ideal. Note that small cell lung cancer tumor increases 1 cm, it is necessary to consult doctor in time for proper treatment under doctor’s advice to prolong patient’s life cycle and control the disease in time.