The prognostic value of systemic immune-inflammation index in surgical esophageal cancer patients: An updated meta-analysis

PURPOSE: To identify the prognostic role of systemic immune-inflammation index (SII) in esophageal cancer patients receiving operation. METHODS: The PubMed, EMBASE, Web of Science, Cochrane Library, WanFang and CNKI electronic databases were searched up to February 17, 2022 for relevant studies. The hazard ratios (HRs) and 95% confidence intervals (CIs) were combined to assess the association between SII and prognosis in surgical esophageal cancer patients. The primary outcome was overall survival (OS) and secondary outcomes were progression-free survival (PFS) and cancer-specific survival (CSS). All statistical analyses were conducted by STATA 15.0 software. RESULTS: A total of nine retrospective studies involving 3,565 participates were included. The pooled results indicated that high SII was significantly related with poor OS (HR = 1.58, 95% CI: 1.23–2.02, P < 0.001). However, subgroup analysis based on pathological type demonstrated that high SII was an independent predictor for poor OS only in esophageal squamous cell carcinoma (ESCC) patients (HR = 1.72, 95% CI: 1.34–2.21, P < 0.001). Besides, SII was also significantly associated with poor PFS (HR = 1.94, 95% CI: 1.61–2.35, P < 0.001) and CSS (HR = 1.44, 95% CI: 1.04–1.99, P = 0.027) in ESCC patients. CONCLUSION: The SII could serve as an independent prognostic factor in surgical ESCC patients and higher SII was related with worse survival. However, more prospective high-quality studies are still needed to verify above findings.