Lead investigator Anne McTiernan, M.D., Ph.D., of Fred Hutchinson Cancer Research Center, presented these findings today at the third annual International Conference on Frontiers in Cancer Prevention Research hosted by the American Association for Cancer Research. "I was surprised by the magnitude of the effect the doubling of breast density associated with combination-hormone therapy," said McTiernan, a member of Fred Hutchinson's Public Health Sciences Division and lead physician of the WHI Clinical Coordinating Center, which is based at Fred Hutchinson.
The effect of HRT on breast density remained consistent throughout the two-year study period and was similar across ethnic and racial groups. The impact was particularly pronounced among women in the highest age bracket; those between 70 and 79 experienced a nearly threefold increase in breast density as compared to younger women, presumably because their breast tissue was less dense to begin with, McTiernan said. "These findings are unique in showing a sustained effect over two years and that even in older postmenpausal women breast density can increase in response to estrogen-plus-progestin therapy," McTiernan said.
The study involved a randomly selected subgroup of 413 racially and ethnically diverse postmenopausal women, ages 50 to 79, who were participants in the WHI estrogen plus progestin trial, which involved more than 16,500 women nationwide.
Half of the women in the sub-study were randomly selected to receive estrogen plus progestin and half received an identical-looking placebo. All received a baseline mammogram at the
Contact: Warren Froelich
American Association for Cancer Research