Metformin Might Improve Colorectal Cancer Survival

BOSTON—Recent clinical studies have suggested that the common diabetes drug metformin holds promise in improving colorectal cancer survival, but the small number of patients and inconsistencies related to diabetic severity have limited the significance of that research.

To remedy that, a new study in the journal Cancer Epidemiology, Biomarkers & Prevention examined the association between metformin use and overall survival (OS) in patients with diabetes and colorectal cancer. The research, led by Tufts Medical Center and the Durham, NC, VAMC, focused on a large population of U.S. veterans and adjusted for measures of diabetic severity.1

For the trial, patients diagnosed with colorectal cancer from January 2001 to December 2008 were identified from the VA Central Cancer Registry.

Overall, 21,352 patients diagnosed with colorectal cancer were identified, including the following numbers:

  • 16,355 nondiabetic patients,
  • 2,038 diabetic patients on metformin,
  • 2,136 diabetic patients on medications other than metformin, and
  • 823 diabetic patients not on antidiabetic medication.

Results indicated that diabetic patients had a significantly worse OS than nondiabetic patients, but metformin users had only a 10% increase in death, with an adjusted hazard ratio of 1.10, as compared with 22% for users of other antidiabetic medications, with an adjusted HR of 1.22.

Among colorectal cancer patients with diabetes, meanwhile, metformin users had a 13% improved OS versus patients taking other antidiabetic medications—adjusted HR of 0.87—while diabetic patients not on any antidiabetic medications did not differ with respect to OS.

“Among diabetics with colorectal cancer, metformin use is associated with improved survival, despite adjustments for diabetes severity and other risk factors,” the study authors concluded, adding that their data lends “further support to the conduct of randomized studies of possible anticancer effects of metformin among patients with colorectal cancer.”

1.    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 Central PMCID: PMC5050110.

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