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.