Bone Mineral Density and Risk of Breast Cancer
January 15, 1997 2 minutes read
Bone Mineral Density and Risk of Breast Cancer
ABSTRACT & COMMENTARY
Synopsis: In a prospective cohort of women over age 65, bone mineral density was a major predictor of risk for breast cancer.
Source: Cauley JA, et al. JAMA 1996;276:1404-1408.
Currently known risk factors for breast cancer are protective factors for future osteoporosis (e.g., age at menarche and menopause). Prospective studies of the relationship between endogenous estrogen concentration and subsequent breast cancer have been inconsistent. One reason for this inconsistency may be that women who use estrogens may be at different risk of breast cancer than non-users.
Based on the premise that an older women’s bone mineral density (BMD) is a useful marker of her exposure to estrogen, Cauley et al hypothesized that higher levels of BMD should be associated with an increased risk of breast cancer. The investigators, as part of a multi-center prospective cohort study of white women over age 65 years, evaluated if BMD was predictive of women developing breast cancer. Women who were users of estrogen replacement therapy (ERT) were excluded from the analysis.
With a mean follow-up of 3.2 years, about 1.2% of women developed breast cancer (4 per 1000 per year). Increased BMD was associated with before and after adjustments for known clinical and family risk factors. In addition, the BMD was incrementally associated with risks. Specifically, the women with the highest BMD had a 2.0-2.5 times greater risk than those with the lowest BMD.
COMMENT BY BRUCE E. HILLNER, MD
This is a very provocative study. It is important and troubling for clinicians. If BMD predicts breast cancer, then a linkage between two of the most common conditions affecting a woman’s health is established. Given the complex calculus of balancing the benefits and risks of ERT, this study highlights the complexities. Future work assessing BMD predictive power in younger women is needed.
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