A new study confirms what many have suspected: that the recent drop in breast cancer cases is because women are stopping hormone replacement therapy. It makes the strongest cause yet that HRT causes breast cancer.
Fred Hutchinson Cancer Research Center researchers co-authored the study.
Valerie Marcon was part of the women's health initiative study that came to an abrupt halt in 2002.
"I never worried about the medication being harmful," she said.
In hindsight, perhaps she should have been concerned. The study showed that women on combination hormone therapy - taking estrogen and progestin - were at much higher risk for breast cancer.
But the study didn't end there. Researchers have continued to follow those women and others taking HRT. The latest findings show both good news and bad news about breast cancer.
"It's clear evidence there's roughly a two-fold elevation in risk after about five years of estrogen plus progestin use and that mainly goes away surprisingly quickly," said Dr. Ross Prentice, Fred Hutchinson.
Goes away two years after stopping hormone therapy. Prentice and other researchers believe that's has had an impact on breast cancer rates.
"A reduction by about 15,000 or 20,000 breast cancer cases per year in the country, a reduction that we see, a rather quick reduction could explain a majority of that within a couple of years if women stopping taking these hormones," said Prentice.
So what does this mean for women who have uncomfortable side-effects from menopause?
"I think the advice to women, to use a low dose in as short period of time as possible is quite sensible of overall benefits and risks, but for breast cancer we really can't say there is a safe period or a safe dose," said Prentice.
The study is published in this week's New England Journal of Medicine.
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