Study Finds that Metformin Reduces Colorectal Cancer Risk in Type 2 Diabetes

Metformin diabetes drug (biguanide class), chemical structureStudies have shown that metformin inhibits cancer cell growth and lowers overall cancer risk and that metformin therapy may actually decrease the risk of cancer and cancer mortality among patients who have type 2 diabetes.

However, the limited data on metformin and its impact on colorectal cancer have been inconsistent.

In a study, Chinese researchers examined the link between metformin therapy and colorectal cancer among patients with type 2 diabetes.

Results of the study were published in the October 2011 issue of Diabetes Care in the article “Reduced risk of colorectal cancer with metformin therapy in patients with type 2 diabetes.”

Investigators pooled data from the PubMed and SciVerse Scopus databases to pinpoint studies that looked at the effect of metformin therapy on colorectal cancer in patients with type 2 diabetes.

This random-effects meta-analysis involved a total of 5 studies, which included 108,161 patients with type 2 diabetes. For the purposes of this study, summary effect estimates were obtained.

Is Metformin Effective at Reducing Risk of Colorectal Cancer?
Researchers observed that metformin was associated with a significantly lower risk of colorectal neoplasm (relative risk [RR]: 0.63 [95% CI: 0.50 to 0.79]; p< 0.001).

After researchers excluded one study (which investigated colorectal adenoma), the remaining 4 studies involved 107,961 patients who had diabetes and 589 incident colorectal cancer cases during follow-up.

It was noted that metformin therapy was associated with a much lower risk of colorectal cancer (RR: 0.63 [95% CI: 0.47 to 0.84]; p=0.002); there was no evidence of the presence of significant heterogeneity between the 5 studies (q=4.86, p=0.30; I2=18%).

The research team indicated that from observational studies, metformin therapy appears to be associated with a considerably reduced risk of colorectal cancer in patients who have type 2 diabetes but further investigation is warranted.

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