Diabetes Rx and Breast Cancer Survival

Breast cancer survival was not extended with metformin use

(RxWiki News) The diabetes drug metformin has been something of a darling in the cancer world of late. Previous research has shown that it may help prevent or beat cancer. But a new study has come along that creates a question mark.

This recent large study has found that taking the diabetes medication metformin did not help older breast cancer survivors with diabetes live longer.

"Make sure all your doctors know your cancer history."

Endocrinologist, Iliana Lega, MD, a research fellow at Women's College Research Institute in Toronto, Ontario Canada, led the study.

"Although existing scientific literature suggests that drug [metformin] may prevent new cancers and death from breast cancer, our study found the drug did not significantly impact survival rates in our patients," Dr. Lega said in a news release.

Metformin, which is sold under various brand names, is a medicine that regulates blood glucose levels in individuals with type 2 diabetes.

The authors noted that previous research found metformin to lower the risk of new breast cancers by 30 percent and also reduce tumor growth in women who did not have diabetes.

For this study, Dr. Lega and colleagues followed breast cancer survivors aged 66 and older who were diagnosed with breast cancer and treated with metformin over a 10-year period from April 1, 1997 to March 31, 2008.

Among the participants, 1,101 women died during the study. A total of 386 (16.3 percent) survivors died of breast cancer.

“Our findings failed to show an association between improved survival and increased cumulative metformin duration in older breast cancer patients who had recent-onset diabetes. Further research is needed to clarify this association, accounting for effects of cancer stage and BMI in younger populations or those with differing stages of diabetes as well as in non-diabetic populations,” the authors wrote.

Adam Brufsky, MD, PhD, professor of medicine at the University of Pittsburgh School of Medicine, told dailyRx News, “While these results are somewhat disappointing, we still await the results of prospective randomized clinical trials testing metformin as adjuvant therapy for breast cancer before we are going to make firm conclusions on its efficacy.”

Findings from this study were published in the May issue of the journal Diabetes Care.

Review Date: 
May 10, 2013