Mammographic density, hormonal therapy and breast cancer risk
In postmenopausal women who start hormonal therapy with estrogen plus progestin (E+P), changes in breast density should be monitored as a possible bellwether of breast cancer risk, say the authors of a new study case-control study. The data are from the Women’s Health Initiative (WHI) and were published in The Journal of National Cancer Institute.
The aim of the analysis was to determine whether mammographic density change associated with initiation of daily estrogen (0.625 mg) plus medroxyprogesterone acetate (2.5 mg) predicts breast cancer risk. In 174 women who later developed breast cancer (cases) and 733 healthy women (controls), mammographic density was assessed with mammograms taken prior to and 1 year after randomization. Logistic regression analyses were used to adjust for confounders and baseline mammographic density, when appropriate.
In women in the E+P arm (97 cases, 378 controls), breast cancer risk rose 3% for each 1% positive change in percent mammographic breast density (odds ratio [OR] =1.03; 95% confidence interval [CI] 1.01-1.06). Breast cancer risk increased 3.6-fold for women in the highest quintile of mammographic density change (> 19.3% increase) (95% CI 1.52-8.56). After adjusting for change in mammography density, the effect of E+P use on breast cancer risk (OR 1.28, 95% CI 0.90-1.82) was eliminated (OR 1.00, 95% CI 0.66-1.51).
“The 1-year change in mammographic density after estrogen plus progestin initiation,” the authors said, “predicted subsequent increase in breast cancer risk.” They noted that all of the increased risk from E+P exposure was mediated through mammographic density change and encouraged physicians to evaluate changes in mammographic density in women who initiate the hormonal therapy and to discuss the breast cancer risk implications with them.