Doctors writing in the British Medical Journal say that a woman's risk of developing breast cancer while taking hormone replacement therapy (HRT) may be lower than first suggested. The 2003 study that exposed the HRT breast cancer link caused much concern but a new analysis based on new data, known as cumulative absolute risk, paints a less gloomy picture. The researchers say that the new figures will help doctors to weigh the benefits and harms of treatment more accurately. The Australian research team, from the New South Wales Breast Cancer Institute, used the latest data to estimate a woman's individual risk of breast cancer up to age 79 years in relation to hormone replacement therapy. The researchers found that use of hormone replacement therapy increases a woman's cumulative risk, but only slightly. They cited figures for three groups which they said demonstrated the reduced risk:
- Use of estrogen only hormone replacement - 6.3 percent
- Five year use of combined therapy starting at age 50 - 6.7 percent
- No HRT - 6.1 percent
Longer term use (10 years) of combined HRT increases the cumulative risk to 7.7 percent, while estrogen only formulations have a minimal effect on risk of breast cancer, even with extended use. The researchers said that one half of Australian, European, or American women taking hormone replacement therapy are taking combined preparations.
The study also found that while the additional breast cancer risk is greater with combined therapy, once hormone replacement therapy is stopped, a woman's breast cancer risk quickly returns that of a non-HRT user of the same age.
Professor John Boyages, Director of the Institute, was cautious in how the findings should be viewed. He did however say that the new figures would give women a clearer picture of the risks associated with HRT. "Although we found the additional breast cancer risk with hormone replacement therapy for an individual is very small, the effect on the general incidence of breast cancer would be greater, especially in populations with high levels of use. The reasons for taking hormone replacement therapy vary and decisions about its use must be made at an individual level. Our analysis provides women and clinicians with better information to make these choices," he concluded.
