reports

The association between metformin therapy and mortality following breast cancer: a population-based study

Toronto, ON, Canada: University of Toronto (masters thesis).

University of Toronto, Toronto, ON, Canada

Metformin has been associated with a reduction in breast cancer incidence, however its effect on mortality following cancer has not been adequately examined. The purpose of this study was to evaluate the impact of metformin therapy on mortality in women with breast cancer. Using Ontario health databases, this retrospective cohort examined the impact of metformin on mortality among women aged 66 years or older with diabetes and breast cancer. After a mean follow-up of 4.5 years, there was no association between cumulative metformin use and either all-cause or breast cancer-specific mortality (HR 0.97, 95% CI 0.92-1.07; HR 0.91, 95% CI 0.81-1.03 respectively per additional year of cumulative metformin use). Though metformin was not associated with a reduction in mortality in our study of older women with breast cancer, there is still a need to examine whether metformin has an effect on mortality in other breast cancer populations.