Meta-analysis of the relationship between preoperative systemic immune inflammation index and prognosis of patients with biliary tract cancer.

OBJECTIVE: To evaluate the prognostic value of preoperative systemic immune-inflammation index (SII) for overall survival, recurrence-free survival, and clinicopathological features in patients with biliary tract cancer (BTC). METHODS: We systematically searched PubMed, Embase, Web of Science, Cochrane Library, and major Chinese databases. Seventeen studies involving 4,965 patients were included. Study quality was assessed using the Newcastle-Ottawa Scale (NOS). Pooled hazard ratios (HR) or odds ratios (OR) with 95% confidence intervals (CIs) were calculated using random- or fixed-effects models. Subgroup, sensitivity analyses, and funnel plots were conducted to explore heterogeneity and assess robustness. RESULTS: High preoperative SII was significantly associated with worse overall survival (OS) (HR = 1.98, 95% CI = 1.76-2.23, p < 0.001) and recurrence-free survival (RFS) (HR = 1.57, 95% CI = 1.34-1.84, p < 0.001). It also correlated with a higher risk of lymph node metastasis (OR = 1.97, 95% CI = 1.52-2.55, p < 0.001), but showed no significant associations with vascular invasion, tumor differentiation, or perineural invasion. CONCLUSION: Preoperative SII is an effective prognostic predictor for BTC, where elevated levels indicate poorer survival outcomes and increased likelihood of vascular and lymph node involvement.