Breast Cancer May Increase Risk for Type 2 Diabetes

TOPLINE:
Breast cancer is linked to 20% higher risk for new-onset type 2 diabetes (T2D) at 5 years after the cancer diagnosis (vs matched control individuals), but the risk for T2D declines by more than half at 15 years (vs matched control individuals), Danish researchers find.
METHODOLOGY:
A population-based prospective cohort study of 74,526 patients with early-stage breast cancer aged ≥ 30 years was conducted to determine their risk for T2D compared with age- and region-matched control individuals (n = 372,639) without cancer and without T2D at 6 months after breast cancer diagnosis.
The primary outcome was the 5-year cumulative incidence of T2D.
TAKEAWAY:
The median follow-up was 8.1 years for patients with breast cancer and 9.5 years for matched control individuals.
The 5-year cumulative incidence of T2D was 3.8% and 3.3% for patients with breast cancer and matched control individuals, respectively. The adjusted hazard ratio (aHR) was 1.20, a 20% increase in the risk.
By 15 years, the aHR of T2D declined by more than half, but it was still higher than control individuals (aHR, 1.09; 95% CI, 1.05-1.12).
The 5-year cumulative risk for incident T2D was 32% higher among pre-menopausal women (aHR, 1.32; 95% CI, 1.17-1.49) compared with control individuals. Post-menopausal women had an aHR of 1.10 (95% CI, 1.01-1.19) compared with control individuals.
Breast cancer treatments may be responsible for the excess risk at 5 years post-diagnosis. Treatment with aromatase inhibitors (aHR, 1.23; 95% CI, 1.15-1.31) and any endocrine therapy (aHR, 1.22; 95% CI, 1.16-1.29) carried the highest risk for T2D compared with matched control individuals.
IN PRACTICE:
The authors concluded that “[Breast cancer] was associated with excess risk for T2D, though of lower magnitude than previously reported. The excess risk was temporary and related to [breast cancer] treatment…”
SOURCE:
The lead and corresponding author is Kasper A. Kjaergaard, MD, of Aarhus University, Aarhus, Denmark. The study appeared in Journal of the National Cancer Institute.
LIMITATIONS:
Limitations included an observational study design.
DISCLOSURES:
No competing interests were disclosed. The funding sources were Novo Nordisk Foundation and the Danish Cancer Society, among others.
 
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