Prognostic value of the preoperative systemic immune-inflammation index for overall survival after Surgical resection in gallbladder cancer: a systematic review and meta-analysis

BackgroundThe systemic immune-inflammation index (SII) reflects the relationship between tumor-promoting inflammation and anti-tumor immunity in various solid malignancies, but the role of SII in Gallbladder cancer (GBC) has yet to be established. The aim of the systematic review and meta-analysis was to clarify the prognostic value of preoperative SII in GBC patients undergoing resection. MethodsThis systematic review and meta-analysis was performed following PRISMA 2020 checklist and we searched PubMed, Embase, Web of Science and Scopus from inception to November 1, 2025. Original studies with English language enrolled adults with resectable GBC undergoing surgical resection and reported preoperative SII with overall survival (OS) as a hazard ratio (HR) comparing high versus low SII. Risk of bias was assessed with the Newcastle-Ottawa Scale (NOS). Random-effects models were applied to pool HRs, and heterogeneity was summarized with I{superscript 2} and {tau}{superscript 2}. We evaluated publication bias with visual inspection of funnel plots and Eggers regression test. ResultsSeven studies (N= 2,153) met inclusion criteria. High preoperative SII was associated with significantly worse OS (pooled HR 2.17; 95% CI 1.55-2.79). with moderate heterogeneity (I{superscript 2} = 26.0%, {tau}{superscript 2} = 0.0285). Results were robust in leave-one-out analyses, and variability in study-specific SII cut-offs accounted for part of the heterogeneity. Certainty of evidence for the primary outcome was moderate, and all included studies were high quality. Conclusionspreoperative SII is an inexpensive, available biomarker that correlated with risk in resectable GBC and is able to identify patients with more aggressive tumor biology despite Surgical surgery. Systematic review registrationPROSPERO CRD420251185808