Hormone therapy skews breast cancer diagnosis

By Andrew Stern

CHICAGO (Reuters) - 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 oestrogen 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 Centre 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 tumours 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.