Postmenopausal women who use estrogen are at increased risk for developing non-cancerous breast disease, according to a report in the Journal of the National Cancer Institute.

This is the only study to date with randomly assigned treatments to examine the impact of estrogen use on the risk of benign disease, lead researcher Dr. Thomas E. Rohan, from the Albert Einstein College of Medicine in the Bronx, New York, told Reuters Health.

“The central finding was that (estrogen) was associated with an increased risk of benign…breast disease. I was not surprised by the finding” since prior studies had suggested that might be the case, he added.

The study involved 10,739 postmenopausal women who were assigned to receive estrogen or inactive “placebo” as part of the Women’s Health Initiative CEE trial. Breast examinations and mammograms were performed at enrollment and then annually.

During an average follow-up period of 6.9 years, 232 cases of benign breast disease occurred, the report indicates. Of these cases, 155 arose in the estrogen group and 77 in the placebo group. Thus, estrogen use roughly doubled the risk of benign disease.

Rohan said that the current findings do not change the take-home message for doctors contemplating estrogen therapy for their patients, namely, that the risks and benefits of treatment need to be weighed on an individual basis. The apparent link with benign breast disease is “another item to add to the risk side of the equation.”

SOURCE: Journal of the National Cancer Institute, April 16, 2008.