Women with type 2 diabetes taking drug long term have 56 percent lower risk of breast cancer

-- Eric Metcalf

Friday, June 11, 2010 (Last Updated: 06/14/2010)

FRIDAY, June 11 (HealthDay News) -- In women with type 2 diabetes, long-term metformin use is associated with a lower risk of breast cancer, according to research published in the June issue of Diabetes Care.

Michael Bodmer, M.D., of University Hospital Basel in Switzerland, and colleagues analyzed data from breast cancer cases and controls drawn from 22,621 women with type 2 diabetes who used oral antidiabetes drugs. The 305 cases had a mean age of 67.5 at cancer diagnosis, and were matched to 1,153 controls without cancer.

The researchers found that the long-term use of at least 40 prescriptions of metformin -- which exceeded five years' worth -- was associated with a lower risk of breast cancer compared to not taking the drug (adjusted odds ratio, 0.44). Short-term metformin use and use of sulfonylureas or other antidiabetes drugs were not associated with a substantially different cancer risk.

"Several clinical studies in pre- and postmenopausal women with or without type 2 diabetes revealed a significantly higher risk of breast cancer in association with hyperinsulinemia and insulin resistance. Furthermore, high fasting insulin levels and obesity have been associated with poor cancer-related outcome. Both the reduction of hyperinsulinemia and growth inhibition via AMP-activated protein kinase activation might explain why metformin therapy seems to be associated with a decreased risk of breast cancer. This has been hypothesized by various authors and is supported by the current findings," the authors write.

The study was funded by a grant from Merck Serono, France, which manufactures metformin.

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Specialties Urology
Hematology & Oncology

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