Hormone Replacement Therapy Associated With Increases in Mammographic Breast Density

Behind the Cancer Headlines®

September 22, 2005

A randomized placebo-controlled study published in the Journal of the National Cancer Institute has found that use of hormone replacement therapy that contains estrogen and progestin for up to 2 years is associated with increases in mammographic breast density. Mammographic density has been associated with decreased sensitivity of mammograms and increased breast cancer risk.

To assess the affect of estrogen-plus-progestin therapy on mammographic density, Anne McTiernan, M.D., Ph.D., of the Fred Hutchinson Cancer Research Center in Seattle, and colleagues examined data from 413 women who had participated in the Women's Health Initiative.

The Women's Health Initiative, a randomized trial in which more than 16,000 women received either estrogen plus progestin or a placebo for the treatment of menopausal symptoms, found that women given the hormones were more often diagnosed with breast cancer and were diagnosed with cancers at more advanced stages. In addition, the frequency of abnormal mammograms was higher among the women given hormones than among those given the placebo.

In the new study, the authors found that mean percent mammographic density increased by an absolute 6% over baseline mammographic density during the first year of hormone therapy but decreased almost 1% in women receiving placebo. After 2 years, the mean changes persisted but were attenuated in both groups. The authors conclude that use of hormone therapy for up to 2 years is associated with increases in mammographic density.

SOURCE:

Journal of the National Cancer Institute, September 21, 2005