Use of the antidiabetic medication metformin was associated with improved survival among U.S. veterans with colorectal cancer being treated for diabetes, a study published in the journal Cancer Epidemiology, Biomarkers & Prevention has shown.1

Although previous research has demonstrated an association between metformin and improved survival in colorectal cancer, those investigations were limited by small sample sizes and confounding caused by severity of patients’ diabetes. Therefore, researchers sought to examine that association in a large population of United States veterans after adjusting for measures of diabetic severity.

For the study, investigators analyzed data from 21,352 patients diagnosed with colorectal cancer between 2001 and 2008 included in the Veterans Affairs Central Cancer Registry. Of those, 16,355 did not have diabetes, 2038 had diabetes and were treated with metformin, 2136 patients with diabetes on medications other than metformin, and 823 patients had diabetes but were not receiving antidiabetic medications.

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Results showed that patients with diabetes had a significantly worse overall survival compared with patients without diabetes; however, patients who took metformin had only a 10% increase in the risk of death vs patients without diabetes (P = .004).

In contrast with those given metformin, patients with diabetes receiving medications other than metformin had a 22% increase in death compared with patients without diabetes (P < .0001).

These findings translate to a 13% improvement in overall survival among metformin users compared with patients taking other antidiabetic medications (P = .003).

There was no significant difference in overall survival between patients with diabetes not on any antidiabetic medications and those who took medications other than metformin (P = .76)

These findings ultimately lend further support to conduct a randomized controlled trial evaluating the impact of metformin on outcomes in patients with colorectal cancer and diabetes.


1. Paulus JK, Williams CD, Cossor FI, Kelley MJ, Martell RE. Meformin, diabetes, and survival among US veterans with colorectal cancer. Cancer Epidemiol Biomarkers Prev. 2016 Aug 5. doi: 10.1158/1055-9965.EPI-16-0312. [Epub ahead of print]