Environmental Risk Factors for Gallbladder Cancer: Field-Wide Systematic Review and Meta-Analysis

BACKGROUND & AIMS: Cholelithiasis is the most well-recognized risk factor for gallbladder cancer (GBC), the predominant biliary-tract malignancy; however, credibility on other modifiable exposures remains uncertain. We performed a field-wide systematic review and meta-analysis on environmental factors associated with GBC. METHODS: We systematically searched Medline/PubMed and Embase up to May 8, 2023, to identify randomized and nonrandomized studies examining environmental factors for GBC. We conducted random-effects meta-analyses focusing on longitudinal studies. Evidence from case-control studies was considered complementary. Evidence credibility was graded by prespecified criteria including the random-effects estimate, 95% confidence interval (CI), P value, statistical heterogeneity, small-study effects, and robustness to unmeasured confounding. Another 39 significant associations showed lower credibility, including different exposure scenarios of tobacco smoking, alcohol consumption, and insufficient physical activity. CONCLUSIONS: This study offers a detailed appraisal and mapping of the evidence on modifiable factors for GBC. Further high-quality prospective studies are essential to validate emerging associations and inform preventive strategies in high-incidence areas. (Systematic review registration: CRD42023434673.).