Metformin Improves Colorectal Cancer Survival in Veterans

BOSTON—Metformin has been associated with improved colorectal cancer survival (CRC), but investigations have been limited by small numbers of patients and confounding by diabetic severity, according to a new study.

An article in the journal Cancer Epidemiology, Biomarker & Prevention reported research examining the association between metformin use and overall survival (OS) in patients with diabetes and CRC in a large population of U.S. veterans, while adjusting for measures of diabetic severity.1

To do that, the study team from Tufts Medical Center in Boston and the Durham, NC, VAMC identified patients diagnosed with CRC from January 2001 to December 2008 from the VA’s Central Cancer Registry. The researchers sought to determine how overall survival was influenced by diabetes and use of blood sugar-lowering medications.

Used in the study were records on 16,355 nondiabetic patients, 2,038 diabetic patients on metformin, 2,136 diabetic patients on medications other than metformin and 823 diabetic patients who were on no anti-diabetic medications.

Results indicate that diabetic patients had a significantly worse OS than nondiabetic patients, but metformin users had only a 10% increase in death, as compared to 22% for users of other anti-diabetic medications.

Among CRC patients with diabetes, metformin users had a 13% improved OS vs. patients taking other anti-diabetic medications, while diabetic patients not on any anti-diabetic medications did not differ with respect to OS.

“Among diabetics with CRC, metformin use is associated with improved survival, despite adjustments for diabetes severity and other risk factors,” according to study authors, who add that their results “lend further support to the conduct of randomized studies of possible anti-cancer effects of metformin among patients with CRC.”

  1. Paulus JK, Williams CD, Cossor FI, Kelley MJ, Martell RE. Metformin, Diabetes, and Survival among U.S. Veterans with Colorectal Cancer. Cancer Epidemiol Biomarkers Prev. 2016 Oct;25(10):1418-1425. PubMed PMID: 27496094; PubMed CentralPMCID: PMC5050110.

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