Metformin shows chemopreventive potential in Asians with diabetes

Metformin use staves off the risk of developing stomach cancer in a Korean cohort of patients with diabetes mellitus (DM), a study reports.

The population comprised 347,895 Koreans (53.5 percent male), among whom 9,891 (mean age, 56.7 years) had diabetes and used metformin while 14,922 (mean age, 54.4 years) were nonusers; the remaining 323,082 (mean age, 51.7 years) were assigned as non-DM controls.

Individuals with DM, regardless of metformin exposure, were more likely to have higher body mass index, glucose levels, alanine transaminase levels, hypertension history, and lower household income compared with controls.

Over a median follow-up of 12.7 years, 5,621 stomach cancers occurred—74 percent in men and 26 percent in women. Metformin nonusers had the highest estimated cumulative incidence of stomach cancer (men vs women: 3.75 percent vs 1.97 percent), whereas controls logged the lowest (2.54 percent vs 0.95 percent). The corresponding rates among metformin users were 2.91 percent in men and 1.53 percent in women.

Multivariable Cox analysis confirmed that both metformin users and controls had a lower risk of developing stomach cancer compared with nonusers. Use of the glucose-lowering drug reduced the risk by about 30 percent in men (hazard ratios [HR], 0.710, 95 percent confidence interval [CI], 0.579–0.870) and women (HR, 0.700, 95 percent CI, 0.499–0.981). The corresponding HRs in controls were 0.879 (95 percent CI, 0.767–1.006) and 0.701 (95 percent CI, 0.544–0.903).

Although unclear, the anticarcinogenic effect of metformin was postulated to be partly mediated by AMPK activation and immune modulation through the mammalian target of rapamycin. [Diabetologia 2017;60:1577-1585; Clin Sci 2012;122:253-270]