As popular thought that after HRT a woman's risk of developing breast cancer increase manifold has been challenged. The team, based at 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. This is known as the cumulative absolute risk.
The inference obtained said that a woman's risk of developing breast cancer while taking hormone replacement therapy may be lower than we think.
Until now, only population risk data have been available, so this analysis will help doctors to weigh the benefits and harms of treatment more accurately.
Cumulative absolute risk of breast cancer falls with increasing age in women who do not take hormone replacement therapy. The average baseline risk (from 40-79 years) is about 7.2% (1 in 14), reducing to 6.1% (1 in 16) at 50 years, and 4.4% (1 in 23) at 60 years.
Use of hormone replacement therapy increases a woman's cumulative risk, but only slightly. For instance, use of estrogen only hormone replacement or short term (about five years) use of combined therapy starting at age 50 hardly affects the cumulative risk (no use 6.1%, estrogen only 6.3%, combined 6.7%).
Use of combined therapy for about 10 years increases the cumulative risk to 7.7%, while estrogen only formulations have a minimal effect on risk of breast cancer, even with extended use. Studies estimate one half of Australian, European, or American women taking hormone replacement therapy are taking combined preparations.
"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," said Professor John Boyages, the Director of the Institute
"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," they conclude.