Lega IC, et al. - This population-based study was performed to assess the effect of diabetes on breast cancer treatments as well as mortality while accounting for other comorbidities. Cancer treatments received were similar between women with and without diabetes. However, breast cancer-specific mortality remained higher among women with diabetes who had longer diabetes duration or preexisting cardiovascular disease. Findings highlighted new information about key risk factors for the poorer prognosis in women with diabetes and breast cancer.