METFORMIN use linked to significantly lower colorectal cancer risk in patients with inflammatory bowel disease, according to a new population-based cohort study.
Patients with inflammatory bowel disease (IBD) are known to carry a higher risk of colorectal cancer (CRC), a concern magnified when diabetes coexists. New evidence from a large nationwide study suggests that metformin use in this high-risk group may offer a substantial protective benefit against CRC.
Using Taiwan’s National Health Insurance Research Database and the Taiwan Cancer Registry, researchers followed over 240,000 adults newly diagnosed with IBD between 2008 and 2019. After applying strict eligibility criteria and performing 1:1 propensity score matching, the analysis focused on 1,695 metformin users and an equal number of matched non-users.
In adjusted time-dependent Cox models, metformin use was associated with a 56% reduction in CRC risk (adjusted hazard ratio [aHR], 0.44; 95% CI, 0.29–0.68). Competing risk models produced consistent results. Furthermore, metformin was linked to a 32% lower all-cause mortality rate (aHR, 0.68; 95% CI, 0.57–0.80). A dose-response relationship was observed, with the highest quartile of cumulative metformin exposure showing a 67% decrease in CRC risk compared to non-users. Notably, the lowest observed CRC risk occurred at a daily intake of approximately 800 mg.
These findings underscore a potential chemopreventive role for metformin in patients with coexisting IBD and diabetes, although the study authors emphasize that causality cannot yet be inferred. Randomized prospective trials will be necessary to confirm these results and assess whether metformin could be integrated into CRC risk-reduction strategies for patients with IBD.
Reference:
Huang YJ et al. Metformin use and risk of colorectal cancer in patients with inflammatory bowel disease: a nationwide, Population-Based cohort study. J Natl Cancer Inst. 2025:djaf165.
