Meta-analysis: Metformin may reduce colon cancer risk in type 2 diabetes

Zhang ZJ. Diabetes Care. 2011;34:2323-2328.

Treatment with metformin has been associated with a significantly lower risk for cancer cell growth, thereby reducing the risk for cancer overall. According to data from a recent meta-analysis, this effect continues in colorectal cancer among patients with type 2 diabetes treated with the drug.

"The results indicate that metformin therapy was associated with an estimated reduction of 37% in the risk of colorectal cancer among patients with type 2 diabetes," the researchers wrote.

Zhi-Jiang Zhang, MD, PhD, of the department of epidemiology and biostatistics in the School of Public Health at Shanghai Jiao Tong University in China, and colleagues pooled available studies on the effect of metformin on colorectal cancer among patients with type 2 diabetes using PubMed and SciVerse Scopus databases. Five studies published from January 1966 to March 2011 that included 108,161 patients were identified.

Metformin was associated with a significantly lower risk for colorectal neoplasm compared with non-metformin treatment (RR=0.63; 95% CI, 0.50-0.79).

Zhang and colleagues excluded one study on colorectal adenoma, which left four studies containing 107,961 patients with diabetes and 589 incident colorectal cancer cases during follow-up. Again, they found that metformin was associated with a significantly lower risk for colorectal cancer (RR=0.63; 95% CI, 0.47-0.84).

According to the researchers, they found no evidence suggesting significant heterogeneity between the five studies (P=.30).

"If metformin therapy ultimately proves effective on reducing the risk of colorectal cancer, it would likely be recommended for the overwhelming majority of diabetes patients for both blood glucose control and cancer prevention," the researchers wrote.

Further investigation into this correlation is warranted, they said.

Disclosure: The researchers report no relevant disclosures.

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