Risk of Breast Cancer After Onset of Type 2 Diabetes

Abstract

OBJECTIVE To examine the risk of breast cancer in pre- and postmenopausal women with type 2 diabetes (T2D). RESEARCH DESIGN AND METHODS This was a population-based retrospective cohort study. Cox regression, stratified by pre- (<55 years) and postmenopausal (≥55 years) status, was used to estimate hazard ratios (HRs) for breast cancer, during earlier (0–3 months) and later (3 months to 10 years) time windows after diabetes index date. RESULTS Compared with women without T2D, HRs for breast cancer were 0.95 (95% CI 0.48–1.86; P = 0.88) and 1.31 (0.92–1.86; P = 0.14) in pre- and postmenopausal women with T2D, respectively, in the early time window, and 0.92 (0.75–1.13; P = 0.45) and 1.00 (0.90–1.11; P = 0.93) in pre- and postmenopausal women with T2D, respectively, in the later time window. CONCLUSIONS We observed a trend toward an increased risk of breast cancer in postmenopausal women with T2D, but only in the time period immediately after diabetes index date.