The association between pre-existing type 2 diabetes and mortality among women with breast cancer

Analysis of the Clinical Practice Research Datalink investigated the association between pre-existing type 2 diabetes (T2D) and cancer-related and all-cause mortality among adult women with newly diagnosed breast cancer between 1998 and 2020, with follow-up until March 2021. Patients were followed from 3 months after breast cancer diagnosis. Among patients with nonmetastatic breast cancer (n=125,268), T2D was associated with a 12% increased risk of breast cancer mortality and a 21% increased risk of all-cause mortality, compared with patients without T2D. Among patients with metastatic breast cancer (n=32,030), T2D was associated with a 22% increased risk of breast cancer mortality and a 24% increased risk of all-cause mortality. In secondary analysis, higher glycated HbA1c was associated higher mortality risk in both the nonmetastatic and the metastatic cohort. The authors conclude that in this large population-based cohort study, T2D was associated with higher mortality among patients with nonmetastatic or metastatic breast cancer.