Abstract: OBJECTIVE：To investigate the significance of systemic immunoinflammatory index (SII) in the clinical diagnosis and progression monitoring of patients with non-small cell lung cancer (NSCLC). METHODS： A total of 60 patients with NSCLC admitted to the Fourth Hospital of Hebei Medical University from December 2020 to February 2024 were selected as the NSCLC group，and the clinical data and hematological indexes of the patients at the time of initial diagnosis were collected. In addition， 20 patients with benign pulmonary nodules without malignant lesions and 30 healthy subjects without benign and malignant tumors were selected as the benign pulmonary nodules group and control group，respectively. Differences in indicators among the three groups were compared，and the expression levels of indicators in benign pulmonary nodules and different TNM stages were analyzed. ROC was used to evaluate the value of inflammatory indicators such as SII and carcinoembryonic antigen (CEA) in the differential diagnosis and prediction on progression of NSCLC. Their correlations with clinical pathological indicators of NSCLC patients. RESULTS：The levels of SII， ratio of neutrophil to lymphocyte (NLR)， ratio of platelet to lymphocyte(PLR)， CEA， neutrophil count (NE) and lymphocyte count (LY) in NSCLC group were significantly higher than those in control group (P <0.05)，and the median values of SII，NLR and NE were significantly higher than those in benign pulmonary nodule group. SII combined with CEA and SII， NLR， PLR， and CEA in combination had the highest clinical value for distinguishing NSCLC from benign disease group and had a higher predictive value for clinical progression of NSCLC than single index detection. The T stage，M stage，and TNM stage were significantly higher in the high SII group and high NLR group compared with the low-SII and low-NLR group (P <0.05)，respectively. Compared with the low PLR group， the T stage was significantly higher in the high PLR group， with a statistical difference (P <0.05). Compared with the low CEA group， the N stage， M stage， and TNM stage were significantly higher in high CEA group，with statistically significant differences (P <0.05). CONCLUSION：Our data shows that SII was related to clinically assisted diagnosis and progression monitoring of NSCLC. The combination of SII and other inflammatory indicators demonstrated higher efficacy in clinically assisted diagnosis and prediction of progression of NSCLC than CEA alone，with higher clinical application value.

Key words: non-small cell lung cancer, systemic immunoinflammatory index, carcinoembryonic antigen, auxiliary diagnosis, progression monitoring