June 3 (HealthDay News) -- Taking a break from hormone therapy before a mammogram doesn't lower the likelihood of being called back for extra imaging, a study including more than 1,700 women aged 45 to 80 has found.

"Postmenopausal hormones make breasts denser -- like young women's breasts -- and make mammograms harder to read," which increases the chance of a false-positive result, Diana S.M. Buist, an associate investigator at Group Health Center for Health Studies in Seattle, explained in a news release from the center.

A false-positive result means that after their initial mammogram, women are called back for more testing that reveals that they don't have breast cancer. Buist noted that false-positive results account for about 25 percent of overall costs of mammograms in the United States.

Previous research suggested that stopping hormone therapy could improve mammography results for postmenopausal women, but this new study, published in the June 2 issue of the Annals of Internal Medicine, found no evidence to support that theory.

Buist and colleagues found that 11.3 percent of women who stayed on hormone therapy before their mammogram were called back for more tests, compared with 12.3 percent and 9.8 percent, respectively, of women who stopped hormone therapy for one or two months before their mammogram.

"We really hoped to find that a brief break in hormone therapy would lower false-positives, and remove unnecessary costs and anxiety by improving mammography. And we're disappointed to find that it didn't," Buist said in the news release. "But we'll keep trying to find ways to reduce recall rates for women -- in hopes of making mammography more effective and ensuring women have to go through the least amount of testing and radiation that's necessary."

SOURCE: Group Health Center for Health Studies, news release, June 1, 2009