TUESDAY, April 5 (HealthDay News) -- In the latest analysis from
the Women's Health Initiative (WHI) study, researchers report that
risks to postmenopausal women who were taking estrogen-only hormone
therapy faded rapidly after they ended the treatment.
The study found that when women stopped taking estrogen, the
risk of stroke and blood clots, which were elevated while they were
on estrogen, dropped quickly in several years of follow-up after
Possibly the most perplexing finding from this latest analysis
is that a
reduced risk of breast cancer persisted in women who had been
on estrogen-only therapy.
"I think the findings are very reassuring. It doesn't appear that women have to be concerned about an increased risk of breast cancer from short-term use of estrogen therapy, and they might have a decreased risk of breast cancer, heart attack, and even dying," said the study's lead author, Andrea LaCroix, a professor of epidemiology and WHI investigator from the Fred Hutchinson Cancer Research Center in Seattle.
Results of the study are published in the April 6 issue of the
Journal of the American Medical Association.
The Women's Health Initiative estrogen-alone trial included
10,739 postmenopausal women between the ages of 50 and 79 who had
previously had a hysterectomy (surgical removal of the uterus).
The women were randomized to receive either estrogen treatment
or a placebo. The study recruited women from 1993 through 1998, and
the planned end of the study was in 2005. However, the study was
stopped in 2004 when researchers realized the therapy was causing
an increased risk of stroke and no apparent health benefits,
according to LaCroix.
For the current analysis, 7,645 women agreed to continue
participating in follow-up visits through 2009.
The good news from this analysis is that risks that increase
while a woman is taking estrogen therapy appear to dissipate
rapidly over time. While the odds of stroke and blood clots
increase while on estrogen therapy, the risk returns to normal
several years after stopping the hormone therapy. Women who had
taken estrogen also had similar rates of heart disease and an
overall risk of mortality compared to women on placebo at
follow-up, according to the study.
One benefit that was seen during the treatment phase of the
trial -- a reduced risk of hip fractures -- didn't persist when the
women stopped taking estrogen.
The benefit that did seem to last, however, was a decreased risk
of breast cancer. Over the entire follow-up period, the incidence
of breast cancer was 0.27 percent in women who took estrogen, and
0.35 percent in women who took the placebo.
LaCroix said it's unclear what the mechanism behind the apparent
protection against breast cancer is. Normally, estrogen is
implicated in the development of breast cancer, not in the
prevention of the disease.
She said this aspect of the study definitely needs more
research, but added of this finding, "It's reassuring, if you're a
woman in your 50s who has menopausal symptoms and a reason for
Dr. Graham Colditz, co-author of an accompanying editorial in
the same issue of the journal and chief of the division of public
health sciences at the Washington University School of Medicine in
St. Louis, said the reduction in breast cancer may be because these
women were already past menopause when the estrogen was given.
"There's an involution of breast cells after menopause, so there
would appear to be fewer bad actors waiting to respond to the
hormones," he said.
The study also found that the use of estrogen produced better
outcomes for younger women than for women in their 70s. Heart
disease risk, colorectal cancer risk and the overall risk of dying
were lower in women in their 50s compared to those in their 70s,
according to the study.
"Women in their 50s -- who are the best candidates for estrogen therapy -- show the best benefit-to-risk profile for short-term use of estrogen therapy," said LaCroix. "We now have a really good set of data on what happens after you stop taking hormones and you can use this information to discuss risks and benefits with your physician," she added.
Colditz isn't so convinced, however. In the editorial, he noted
that the International Agency for Research on Cancer had concluded
that the body of evidence suggests that estrogen-only hormone
therapy and combination HRT are carcinogenic, and added that this
study did not address longer-term estrogen hormone therapy use,
which a meta-analysis of 16 studies has linked with an increased
risk of breast cancer. In addition, he and his co-author wrote, the
study showed "no substantial benefit" to women who undergo estrogen
hormone therapy, compared to women who do not.
"Women should use estrogen with caution," Colditz concluded. "There are risks from taking hormone therapy. Even when using estrogen for one to two years for relief of menopausal symptoms, there are still risk-benefit issues to deal with."
For more on menopause and hormone therapy, visit the
U.S. Food and Drug Administration.
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