MONDAY, Jan. 31 (HealthDay News) -- Women who begin hormone
therapy at menopause, or before, face a greater risk for breast
cancer than those who start the treatment later, a new study has
Though a number of earlier studies had concluded that hormone
therapy increases breast cancer risk, the researchers wanted to
know whether the timing of the therapy influences that risk,
something they said few studies had examined.
To do that, they analyzed data from 1.13 million participants in
the Million Women Study in the United Kingdom, concluding that the
length of time between menopause and starting hormone therapy has a
"substantial" effect on breast cancer risk.
Compared with women who began hormone therapy before or soon
after menopause, those who started hormone therapy five years or
more after menopause had little or no increased risk, the study
found. The difference in risk was evident regardless of the type of
hormone therapy, how long women used it and whether women were
normal weight, overweight or obese.
The findings, published online Jan. 28 in the
Journal of the National Cancer Institute, support similar findings from the Women's Health Initiative study in the United States, two experts wrote in an accompanying editorial.
The American Cancer Society has more about
hormone therapy and breast cancer risk.