Loading...
The oral antidiabetic drug metformin has demonstrated anticancer activity in limited studies. To investigate whether metformin use is associated with reduced risk for gastric cancer, researchers in Korea used national insurance claims data to retrospectively assess cancer incidence in metformin users versus nonusers among 40,000 patients with type 2 diabetes. Among a total of 7000 regular insulin users, 5900 had used metformin, and among 33,000 insulin nonusers, 27,000 had used metformin.
Gastric cancer incidence was lower in patients taking metformin compared with those not taking metformin among insulin nonusers (P=0.047) but not among regular insulin users. In a multivariate regression model, longer duration of metformin use was associated with reduced risk for gastric cancer (adjusted hazard ratio, 0.88; 95% confidence interval, 0.81–0.96). In a second model that assessed duration of use in blocks of time, metformin use >3 years was associated with reduced risk for gastric cancer (adjusted HR, 0.57; 95% CI, 0.38–0.87).
Kim Y-I et al. Long-term metformin use reduces gastric cancer risk in type 2 diabetics without insulin treatment: A nationwide cohort study. Aliment Pharmacol Ther 2014 Apr; 39:854. (http://dx.doi.org/10.1111/apt.12660)
Comment
A few study limitations should be noted. The overall and annual data analyses barely achieved statistical significance. Also, because of inherent confounding in retrospective database studies, results should be interpreted with caution. Compared with the main findings, those showing reduced cancer risk with long-term use of metformin are more compelling and consistent with reduced risks for cancers in other studies. However, perhaps most compelling was the finding that gastric cancer risk was doubled in insulin users versus nonusers, regardless of metformin use. Understanding the mechanisms by which both insulin and metformin might affect cancer risk requires additional study.