Breast Cancer-Related Deaths Not Affected by Use of Metformin: A Study

Metformin, a drug used to treat type 2 diabetes, has no effect on in the reduction of breast cancer mortality, a new study published in the journal Diabetes Care states.

Once believed to have either direct or indirect tumor-suppressing mechanisms, the purpose of the study carried out by researchers from the Women's College Hospital in Toronto was to evaluate the effect of the metformin therapy on survival in women with breast cancer using methods that accounted for the duration of treatment with glucose-lowering therapies, the researchers explain in the report's abstract.

This population-based study using Ontario health care databases recruited women 66 years or older diagnosed with diabetes and breast cancer between 1997 and 2008.

Then, using Cox regression analyses - a method for investigating the effect of several variables in regards to an event - the researchers explored the association between cumulative duration of past metformin use and breast cancer mortality.

In all, 2,361 breast cancer patients were identified with a mean age at cancer diagnosis of 77 years and a mean follow-up of 4.5 years.

From this group, 46 percent or 1,101 died, among which 386 died as a result of their breast cancer.

Based on these cases, the researchers did not find a significant association was between cumulative duration of past metformin use and all-cause or breast cancer-specific mortality per additional year of cumulative use.

"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," the researchers explain in the abstract.

However, far from being the last word, the group argues that more studies should be conducted on the topic among other demographics, including younger populations or those with differing stages of diabetes as well as in nondiabetic populations.