Post-breast cancer, metformin has no effect on mortality

(HealthDay)—For older women with diabetes and breast cancer, there is no association between metformin use and all-cause or breast cancer-specific mortality, according to a study published online April 30 in Diabetes Care.

Iliana C. Lega, M.D., from the Women's College Hospital in Toronto, and colleagues conducted a population-based study involving 2,361 women aged 66 years or older diagnosed with diabetes and breast cancer. The correlation between cumulative duration of past metformin use and all-cause and breast cancer-specific mortality was assessed.

During a mean follow-up of 4.5 years, the researchers identified 1,101 deaths (46.6 percent), of which 16.3 percent were breast cancer-specific. There was no significant association observed between cumulative duration of past metformin use and all-cause or breast cancer-specific mortality.

"In summary, we conducted a large population-based study to investigate the effects of metformin therapy on mortality after breast cancer in a diabetic population," the authors write. "Cumulative exposure of metformin was not significantly associated with all-cause or breast cancer-specific mortality in our incident diabetic cohort when modeled as a time-varying covariate."