Increasing risk of diabetes mellitus in postmenopausal women with newly diagnosed primary breast cancer

Abstract Aims/Introduction We sought to determine if postmenopausal women who develop breast cancer are at increased risk of developing diabetes mellitus. Materials and Methods The Taiwan National Health Insurance Research Database was searched from 2001 to 2015 for women aged ≥55 years (postmenopausal) with a diagnosis of primary breast cancer. Participants were age‐matched with women without breast cancer in a 1:5 ratio. Cox proportional hazards analyses were used to examine associations between breast cancer, risk factors and the development of diabetes mellitus. Results A total of 4,607 women with primary breast cancer and 23,035 age‐matched controls without breast cancer were included (mean age 58.6 ± 9.1 years). Adjusting for age, income, urbanization, Charlson Comorbidity Index and medical conditions, the risk of diabetes mellitus for participants with breast cancer at 1, 5, 10 and 15 years was 1.70‐, 1.34‐, 1.27‐ and 1.24‐fold higher, respectively, than for participants without breast cancer (adjusted hazard ratio [aHR] 1.70, 95% confidence interval [CI] 1.40–2.05; aHR 1.34, 95% CI 1.17–1.54; aHR 1.27, 95% CI 1.13–1.44; aHR 1.24, 95% CI 1.11–1.40). The risk of diabetes mellitus at 1 year for breast cancer patients receiving hormone therapy was 1.22‐fold higher than in those not receiving hormone therapy (aHR 1.22, 95% CI 0.86–1.74), but without statistical significance. Conclusions Postmenopausal women with breast cancer are at increased risk of developing diabetes mellitus, independent of receiving hormone therapy, and should be closely monitored to establish an early diagnosis and therapeutic intervention for improving related outcomes.