Abstract: Objective To investigate the value of system immune-inflammation index（SII） in the prognosis of patients with advanced non-small cell lung cancer（NSCLC）. Methods Clinical data of 300 patients with advanced NSCLC who were admitted to the Chengde Medical College Affiliated Hospital from October 2013 to December 2018 were collected. ROC curve was used to calculate the best SII cutoff value，and patients were divided into high SII group（SII≥767.24×10⁹，n=168） and low SII group（SII＜767.24×10⁹，n=168）according to the best cutoff value . The clinicopathological characteristics and overall survival of the two groups of patients were compared，and the relationship between SII and prognosis was analyzed by Cox regression. Results SII was associated with clinical staging and KPS score（P<0.05）. The median survival in the low SII group was higher than that in the high SII group（21 months vs 13 months，χ²=16.824，P<0.001）.Univariate Cox regression showed that pathological type，clinical stage，smoking，KPS score，SII，Hb level and treatment regimen were all associated with the prognosis of advanced NSCLC patients（P<0.05）. Multivariate Cox regression showed that SII≥767.24×109 was an independent risk factor for the overall survival of advanced NSCLC patients（HR=1.416，95%CI：1.039-1.930，P=0.028）. Conclusion High SII is an independent risk factor for the overall survival of patients with advanced NSCLC，which can be used as a prognostic indicator.

Key words: Non-small cell lung cancer, System immune-inflammation index, Prognosis