Abstract
BACKGROUND: The objective of this study is to explore the association between the pretreatment systemic immune-inflammation index (SII) and prognosis in non-small cell lung cancer (NSCLC) patients. METHODS: A systemic literature search of PubMed, EMBASE, the Web of Science, the Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang, VIP and SinoMed databases was performed from January 1, 1966 to April 15, 2019, to identify potential studies that assessed the prognostic role of the pretreatment SII in NSCLC. The hazard ratio (HR) and 95% confidence interval (CI) were combined to evaluate the correlation of the pretreatment SII with overall survival (OS), disease-free survival (DFS), progression-free survival (PFS) and cancer-specific survival (CSS) in NSCLC patients. RESULTS: A total of 9 studies involving 2,441 patients were eventually included. An elevated pretreatment SII indicated significantly poorer OS (HR =1.88, 95% CI: 1.50-2.36; P<0.001) with high heterogeneity (I(2)=60.6%, P=0.019), DFS/PFS (HR =2.50, 95% CI: 1.20-5.20; P=0.014) with high heterogeneity (I(2)=58.2%, P=0.092) and CSS (HR =1.852, 95% CI: 1.185-2.915; P=0.007). Subgroup analyses further verified the above results. In addition, compared with the neutrophil to lymphocyte ratio (NLR) and the platelet to lymphocyte ratio (PLR), the SII showed a much higher prognostic value in NSCLC. CONCLUSIONS: The pretreatment SII may serve as a useful prognostic indicator in NSCLC and contribute to prognosis evaluation and treatment strategy formulation. However, more well-designed studies are warranted to verify our findings.