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Metformin Fails to Improve Survival Rates in Breast Cancer Patients

May 30, 2013

In a select sample of breast cancer patients, the possible anti-cancer effects of metformin do not significantly increase survival rates…. 

Metformin, a mainstay drug in the treatment of diabetes, has recently gained attention for its potential to improve survival from or even prevent cancer. However recent results from a study conducted by the Women’s College Research Institute have found that the drug did not significantly improve the survival rates of women suffering from breast cancer.

It has been suggested through scientific research that metformin may in fact reduce the growth of new cancers and even suppress breast cancer growth in non-diabetic patients. Lead research author, Dr. Iliana Lega, studied 2,361 women diagnosed with breast cancer in order to determine the anti-cancer properties of metformin. She reported, "Understanding the effects of metformin on breast cancer patients is critical in helping address the gap in cancer outcomes in patients with and without diabetes."

The study focused on women 66 years of age and older diagnosed with diabetes and breast cancer between 1 April 1997 and 31 March 2008. The analysis each individual started from the date of breast cancer diagnosis until their death or until March 30, 2010. Cox regression analyses were used to determine the association between cumulative duration of past metformin use and all-cause and breast cancer-specific mortality. Unfortunately, the authors reported no significant association found between the past use of metformin and all-cause mortality or breast cancer-specific mortality.

Dr. Lega notes that this study is unique in that it is one of the first to look at the effects of metformin use in diabetic women diagnosed with breast cancer compared to previous research done in non-diabetics. The authors note that further research is needed to account for potential effects of cancer stage, BMI, age and even non-diabetic status of individuals in order to determine an association with the use of metformin.

Association Between Metformin Therapy and Mortality After Breast Cancer: A Population-Based Study. Diabetes Care, 2013