The role of preoperative systemic immune-inflammation index in predicting the prognosis of patients with digestive tract cancers: A meta-analysis

Background: Systemic immune-inflammation index (SII) is correlated with prognosis in several types of cancers. In this study, we conducted a meta-analysis to systematically evaluate the prognostic significance of SII in digestive tract cancers. Methods: PubMed, Web of Science, Embase and Cochrane databases were searched for articles reporting an association between preoperative SII and the survival of patients with digestive tract cancers. The baseline information was extracted, with overall survival (OS), disease-free survival (DFS), progression-free survival (PFS), and cancer-specific survival (CSS) as outcome indicators. The hazard ratio (HR) was used to calculate the relationship between SII and patient survival. Results: On the basis of specified inclusion and exclusion criteria, a total of 17 eligible studies covering 8384 patients were included in this meta-analysis. The meta-analysis showed that high preoperative SII was associated with low OS (HR = 1.86, 95% confidence interval [CI] = 1.57-2.21) and DFS (HR = 2.03, 95% CI = 1.63-2.52) in patients with digestive tract cancers. Subgroup analysis indicated that higher SII was consistently associated with lower OS regardless of geographic region, sample size, disease type, or SII thresholds. Conclusions: Systemic immune-inflammation index can act as a reliable prognostic indicator in patients with digestive tract cancers.