"Hopefully, it will convince women to reconsider," said Dr. Susan Hendrix of
Wayne State University in Detroit, a co-author of the new analysis. "We've got
to find a better way to help women with their menopausal symptoms."
Some previous studies suggested breast tumors might be less aggressive in
hormone users; other studies indicated the opposite. Previous research also
suggested that hormones might make breast tissue more dense, hindering the
detection of tumors.
Seeking more definitive answers, the researchers took a closer look at data
from the government's landmark Women's Health Initiative study, which was halted
last summer after it was found that estrogen-progestin pills raise the risk of
heart attack, strokes and breast cancer.
While last summer's findings led many women to stop taking hormones, Hendrix
said an estimated 3 million women still use them, primarily to relieve hot
flashes and other symptoms of menopause.
The latest findings appear in Wednesday's Journal of the American Medical
Association.
The analysis involved 16,608 women ages 50 to 79 who used either combined
hormone treatment or dummy pills for an average of five years.
As of January, breast cancer had developed in 245 women who used the combined
hormone treatment and in 185 women who had taken dummy pills.
Hormone users' tumors were larger at diagnosis, 1.7 centimeters on average
versus 1.5 centimeters in placebo women. Tumors had begun to spread in 25.4
percent of hormone users, compared with 16 percent of placebo women.
The researchers said this appears to mean that in women on
estrogen-progestin, the tumors both grow faster — that is, they are more
aggressive — and escape detection longer.
Overall, women on both hormones faced a 24 percent increased risk of breast
cancer — equal to eight extra cases of cancer per year for every 10,000 women
taking the pills.
The increased risk did not appear in the first two years of treatment. But
Hendrix said the tumors may have been present early on but were not detected
until later because of hormone-induced breast density.
The new analysis did not examine breast density. But researchers think
progestin may be the culprit because it can cause breast cells — both normal and
abnormal — to proliferate, an effect that may be accentuated when the hormone is
combined with estrogen.
Wyeth Pharmaceuticals, maker of the Prempro pills used in the study, said
hormones remain an appropriate therapy when used at the lowest possible dose for
the shortest possible time.
The latest analysis is by far the most conclusive, said Dr. Peter Gann, an
associate professor of preventive medicine at Northwestern University who was
not involved in the study.
It "further worsens the news for long-term hormone replacement therapy. It
suggests the excess breast cancer risk is not trivial," Gann said.
Last summer's Women's Health Initiative findings shattered long-held beliefs
that hormones are good for women's hearts. Last month, another analysis of data
from the study found that instead of sharpening the mind, hormones may double
the risk of Alzheimer's and other forms of dementia.
A second, smaller study in Wednesday's journal also confirmed a link between
combined hormone treatments and breast cancer and suggested estrogen-only
treatment may be safer.
The study involved 975 Seattle-area women ages 65 to 79. The greatest breast
cancer risk was in women who used estrogen-progestin for at least five years,
even if they took the progestin component only some days a month.
Those who used estrogen alone, even for 25 years or longer, showed no
appreciable increased risk, according to the study, led by Dr. Christopher Li of
Fred Hutchinson Cancer Research Center in Seattle.
Estrogen alone is recommended only for women with hysterectomies because it
can cause uterine cancer unless balanced by progestin.
The researchers said more definitive answers will come from the continuing
estrogen-only part of the Women's Health Initiative study.
