High BMD fails to predict breast cancer risk in Austrian cohort

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Takeaway

  • There was no association between high bone mineral density (BMD; vs low BMD) in early postmenopausal women and excess breast cancer incidence or mortality.

Why this matters

  • The findings do not support the hypothesis that high BMD reflects longer exposure to estrogen, and thus should predict breast cancer risk.

Study design

  • Prospective cohort of 3446 women participating in a medical prevention program in western Austria.
  • BMD assessed at the lumbar spine by dual-energy X-ray absorptiometry or quantitative CT.
  • Funding: None disclosed.

Key results

  • No association found between higher BMD quartiles (vs lowest quartile) and breast cancer incidence (median follow-up, 20.7 years).
    • highest BMD quartile (vs lowest BMD quartile) was associated with a nonsignificant reduction in breast cancer onset when follow-up was limited to the first 10 years after BMD measurement (HR, 0.53; 95% CI, 0.25-1.12), but not when follow-up was started 10 years after BMD measurement (HR, 0.97; 95% CI, 0.52-1.78).
  • No association found between higher BMD quartiles (vs lowest) and all-cause mortality after breast cancer or breast cancer-specific mortality (BCSM).
    • The highest BMD quartile (vs lowest) had the lowest, albeit nonsignificant, all-cause mortality (HR, 0.81; 95% CI, 0.25-2.62) and BCSM (HR, 0.39; 95% CI, 0.06-2.33) after adjustment for age.

Limitations

  • Observational design.
  • Only included early postmenopausal women.