Is metformin use associated with a reduced risk of oesophageal cancer? A systematic review and meta-analysis

Objectives Studies on the association between metformin use and the risk of oesophageal cancer (OC) have generated controversial findings. This updated meta-analysis was conducted to reassess the effects of metformin on OC. Methods A comprehensive search strategy was conducted to select relevant studies from origination to February 2021. Heterogeneity was evaluated through the Q test and I-2 statistics. HRs and 95% CIs were pooled through either random-effect or fixed-effect models. Meta-regression, subgroup analyses, sensitivity analysis and publication bias diagnosis were also performed. Results Seven studies with 5 426 343 subjects were included. Metformin use was associated with reduced risk of OC (HR=0.69, 95% CI 0.54 to 0.87, p<0.001). Sensitivity analysis suggested that the results were relatively stable. Conclusion Metformin is associated with a reduced risk of OC. More well-designed studies are still needed to further elaborate on these associations. PROSPERO registration number CRD42021237127.