CHICAGO - Women on hormone replacement therapy have only a slightly higher risk of developing breast cancer, but there are much greater chances they will experience the worry of abnormal mammograms or may undergo an avoidable breast biopsy, researchers said on Monday.

Mammograms and biopsy exams were also found to be less reliable at detecting breast cancer among women taking hormones, which counteract symptoms of menopause such as hot flashes and vaginal dryness.

Originally, the 2002 Women's Health Initiative study involving 16,608 women aged 50 to 79 found breast cancer incidence among women taking the hormones estrogen and progestin projected to an additional one in 1,000 cases compared to women taking an inert placebo.

"What this data does is emphasize that yes, the breast cancer risk is still there, but more importantly, instead of that low number of one in 1,000 getting breast cancer, one in 10 women are told they had an abnormal mammogram they'll have to deal with, and probably even more importantly, one in 25 women will have an otherwise avoidable breast biopsy," Dr. Rowan Chlebowski at the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center said in a telephone interview.

"Both of those less reliably found cancer," he added.

Previous research has shown hormone replacement therapy increases breast tissue density, which can make detection of cancerous tumors more difficult, although the current study did not examine this factor.

Since the original findings of increased cancer risk, doctors generally have urged women opting for hormone therapy to use it at the lowest effective dose for the shortest possible time.

Roughly 25 million U.S. prescriptions for hormone therapy are written yearly, Chlebowski said.

The pharmaceutical company Wyeth said in a statement the study's findings did not change what is already known about the breast cancer risk from hormone replacement therapy.


"These findings represent a concern for post-menopausal women who are considering hormone therapy," Chlebowski said in a statement. "They should take the results of this study into consideration and consult with their physicians before undergoing even short-term hormone therapy."

In the study published in the Archives of Internal Medicine, 35 percent of women taking hormones had mammograms with abnormal results compared to 23 percent of women taking a placebo. An abnormal test can create emotional as well as financial hardships, the study noted.

Ten percent of women taking hormones had breast biopsies ordered by their doctors, compared to 6 percent of women taking a placebo.

During the 5-1/2 years of the study, there were 199 breast cancers found in the hormone group and 150 in the placebo group. Women taking hormones had more advanced cancers yet biopsies ordered by their doctors had a lower rate of diagnosis -- 15 percent in the hormone group versus 20 percent in the placebo group.

"(A year) after discontinuation (of the therapy) ... the adverse effects on mammogram and breast biopsy performance were seen even in younger women in the fifth decade of life, so the finding may impact women just entering menopause as well," Chlebowski said.

(Editing by Eric Walsh)