Small cell lung cancer is the most serious type of lung cancer because small cell lung cancer has a very high malignancy and rapid proliferation index, and is prone to distant metastases such as bone metastases, liver metastases, brain metastases and other distant metastases, thus losing the means of treatment because surgical resection is the main treatment for lung cancer. Small cell lung cancer has no chance of radical surgical resection because distant metastasis occurs at an early stage, thus the prognosis is very poor. Of course, small cell lung cancer is more sensitive to radiotherapy and chemotherapy, which means that radiotherapy and chemotherapy can rapidly make the tumor fade away, thus improving the progression-free survival time of small cell lung cancer to a certain extent. Of course, in spite of this, small cell lung cancer still develops early and extensive metastasis due to its biological characteristics, which affects the life expectancy of patients.