Prognostic value of systemic immune-inflammatory index in survival outcome in gastric cancer: a meta-analysis

Background: In recent years, many studies have reported that the systemic immune-inflammatory index (SII) can be used to predict the prognosis of cancer patients; however, this finding remains controversial in gastric cancer (GC). Therefore, the purpose of this study was to systematically and comprehensively probe the prognostic role of SII in GC. Methods: Relevant publications were extracted from PubMed, EMBASE, Cochrane Library databases, and WANFANG DATA (Chinese database). The included studies had patients with pathologically confirmed GC and long-term follow-up data. The patient's outcome was death, recurrence, or status at the end of follow-up. The studies included randomized controlled tests, case-control studies, or cohort studies using a multivariate proportional hazard model adjusted for survival outcomes. Cochran's Q test and Higgins' I-squared statistic were performed to assess heterogeneity. Publication bias was assessed by visual inspection of a Begg's funnel plot. Results: A total of 6,925 patients in 11 studies were included. The pooled hazard ratio (HR) indicated that a higher SII value was significantly associated with worse overall survival (OS) [HR: 1.53, 95% confidence interval (CI): 1.27-1.83] and worse disease- free survival (DFS) (HR: 1.57, 95% CI: 1.24-1.97) in GC patients. In the subgroup analysis, the HR was 1.72 (95% CI: 1.51-1.95) and 1.27 (95% CI: 0.96-1.67) in the group of patients aged <59 and >= 59 years, respectively. Conclusions: The pooled HR indicates that a higher SII in younger patients with GC predicts a poor prognosis. In elderly patients with GC, the prognostic role of SII needs further research.