Abstract: Small cell lung cancer is a relatively high malignant tumor among lung cancers,and the high incidence of brain metastases has been paid great attention for a long time.To address this situation,prophylactic cranial irradiation (PCI) has been proposed and applied in the treatment of small cell lung cancer for many years.However,neurotoxicity after radiotherapy has been greatly controversial.Recent[y,a number of scholars argue that neurotoxic symptoms of PCI are caused by a variety of factors.Considering the exact effect of PCI on improving patients' survival time,the exact value of PCI in clinical application should be affirmed.