Systemic immune inflammation index and gastric cancer prognosis: A systematic review and meta‑analysis

The present study aimed to pool the available data on the associations between the systemic immune inflammation index (SII) and overall survival (OS) or recurrence-free survival (RFS) in patients with gastric cancer (GC). A systematic search was conducted in the PubMed, EMBASE and Scopus databases for observational studies, and a random effects model was used to conduct the statistical analysis. Pooled effect sizes were reported as hazard ratios (HRs) with corresponding 95% confidence intervals (CI). Data from 30 studies (24 conducted in China) with follow-ups ranging between 15.5 and 65.6 months were analyzed. Patients with GC and high SII levels had poor OS (HR, 1.53; 95% CI, 1.34-1.75) and recurrence free survival (HR, 1.41; 95% CI, 1.17-1.70). These increased risks were present irrespective of the treatment strategy (surgical or non-surgical management), the sample size (<500 and ≥500) and the cut-off used to define high and low SII (<600 and ≥600 x10⁹ cells/l). The results of this meta-analysis suggest that high pretreatment SII levels were associated with poor OS and RFS in patients with GC.