For patients with diabetes in the United States, metformin use is associated with reduced risk of developing colorectal cancer (CRC), according to a study published in Cancer.

Amikar Sehdev, M.D., M.P.H., from the University of Chicago, and colleagues examined the effects of metformin on CRC incidence in a U.S. population.

Patients with diabetes and CRC were identified from MarketScan databases. Each case was matched for age, sex, and geographical region with up to two controls; the mean age of study participants was 57 years for cases and 55 years for controls (P = 1.0).

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In each group, about 60 percent of participants were male and 40 percent were female. Prescription tracking within the 12-month period before the index date was used to assess metformin exposure.

The researchers found that any metformin use correlated with a 15 percent reduction in the odds of CRC in the multivariable model (adjusted odds ratio, 0.85; 95 percent confidence interval, 0.76 to 0.95; P = 0.007).

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The beneficial effect of metformin use was reduced to 12 percent after adjustment for health care use (adjusted odds ratio, 0.88; 95 percent confidence interval, 0.77 to 1.00; P = 0.05).

There was no significant association with metformin dose, duration, or total exposure in dose-response analyses.

“Metformin use appears to be associated with a reduced risk of developing CRC among diabetic patients in the United States,” the authors write.


  1. Sehdev, Amikar, MD, MPH, et al. “Metformin for primary colorectal cancer prevention in patients with diabetes: A case-control study in a US population.” Cancer. DOI: 10.1002/cncr.29165. November 25, 2014.