Association of Aspirin, Metformin, and Statin use with gastric cancer incidence and mortality: A nationwide cohort study

Anticancer effects of aspirin, metformin, and statins against gastric cancer, one of the most common cancers in the world, have been reported. This retrospective cohort study aimed to investigate independent associations of aspirin, metformin, and statin use with gastric cancer incidence and mortality after adjustment for concomitant use of other drugs, using pooled cohort data extracted from the Korean National Health Insurance claimdatabase. Follow-up started on January 1, 2004 and ended at the date of gastric cancer diagnosis, death, or December 31, 2013. Exposures to drugs were defined as cumulative duration of use for aspirin and cumulative defined daily dose formetformin and statin, and were entered as time-dependent variables in Cox analysis models to avoid immortal time bias. Use of aspirin for longer than 182.5 and 547.5 days during 2-year interval was associated with reduced risks of gastric cancer incidence and mortality, respectively. Patients with diabetes were at higher risk of gastric cancer incidence and mortality than nondiabetic people, regardless of metformin treatment. However, metformin use among patients with diabetes was associated with a reduction in gastric cancer mortality in a dose-response manner. Statin use was also associated with a reduction of gastric cancer mortality in the general population, but not with gastric cancer incidence. In conclusion, long-term use of aspirin was independently associated with reduced incidence and mortality of gastric cancer in the general population, but metformin or statin use was only associated with a reduction of gastric cancer mortality in patients with diabetes and in the general population, respectively.