NEW YORK, Jan 25 (Reuters Health) -- The potential benefits of taking
hormone replacement therapy beginning at menopause are many, ranging from relief
from hot flashes to lowering the risks of heart disease and the brittle-bone
disease osteoporosis. However, taking hormones remains controversial since some
studies have linked the treatment with an increased risk of breast cancer.
Now, results of a study published in the January 26th issue of The Journal
of the American Medical Association suggest that women who take estrogen in
combination with the hormone progestin are at greater risk of developing breast
cancer than women who take estrogen alone. For women who still have a uterus,
progestin is often prescribed along with estrogen, since estrogen alone can
increase the risk of cancer in the endometrium, the lining of the uterus.
"It's been unclear and controversial what the effects of progestin are on
the breast," one of the study's authors, Dr. Catherine Schairer, an
epidemiologist at the National Cancer Institute in Rockville, Maryland, told
Reuters Health in an interview. "This study suggests that estrogen-progestin may
increase breast cancer risk beyond that of estrogen alone."
But another epidemiologist who spoke with Reuters Health said that women
taking hormone replacement therapy should not be worried about the results of
the study.
Schairer and her colleagues based the conclusions on follow-up interviews
and questionnaires from 46,355 postmenopausal women who were enrolled in a
national breast cancer screening program. To determine the risk of breast
cancer, they compared 2,082 women who developed the disease between 1980 - 1995
with women who had no history of the cancer.
Compared with women who did not take hormone replacement therapy, those
who took estrogen-progestin recently -- either currently or within the previous
4 years -- had a 40% higher risk of breast cancer after the researchers took
into account other risk factors such as age at menopause, education and history
of having mammograms. The risk was 20% greater in women who took estrogen alone
than in those who did not take any hormone replacement therapy.
The investigators found that the risk of breast cancer increased the
longer women took hormone replacement therapy. For those who had recently taken
estrogen alone, the risk of breast cancer increased by 1% for each year of use.
The risk per year was significantly higher for recent users of estrogen and
progestin --8% a year.
But the difference between the two types of hormone therapy was only
statistically significant in leaner women, not those who were overweight or
obese. In her comments to Reuters Health, Schairer said that there were not
enough heavier women in the study who had taken combination therapy to get
accurate results.
She said that more research is needed to make firm conclusions about
hormone replacement therapy and breast cancer risk. "We need to evaluate
longer-term use of estrogen in combination with progestin," she said in the
interview. Schairer added that it would be important to study different types of
combination therapy. Among women who take both estrogen and progestin, not all
take progestin on a daily basis.
Regardless of hormone use, Schairer said, "It's very important for all
women to get periodic (breast cancer) screening."
"Women on hormone replacement therapy should be particularly careful," she
said.
Noting that the study indicates that the risk of breast cancer increases
with longer use of hormone replacement therapy, Dr. Walter C. Willett from
Harvard School of Public Health in Boston, Massachusetts, and colleagues write
in an accompanying editorial that the results of the study will have a major
impact on weighing the benefits and risks of hormone replacement. While hormone
therapy is often prescribed to benefit the bones and heart, the risks of hip
fracture and heart disease take a decade or more after menopause to become
large, they note.
For women who use hormones for 2 to 3 years to relieve hot flashes and
other symptoms of menopause, the risk of cancer should not be a major concern,
according to the editorialists. But for women who still have a uterus, the risks
and benefits of long-term use of hormone therapy should be carefully examined,
they write.
But Dr. Trudy Bush, an epidemiologist at the University of Maryland School
of Medicine in Baltimore, told Reuters Health in an interview, "Women should not
be afraid of this report. If they are on hormone replacement therapy, they
should continue."
The majority of studies examining hormone therapy have not detected an
increased risk of breast cancer, she said. While this study shows a small
connection, it is important to look at the big picture, which does not confirm a
risk, she said.
Bush pointed out that estrogen-progestin therapy contains only about 25%
of the hormones in oral contraceptives, which have not been linked to an
increased risk of breast cancer. She also said that during pregnancy a woman is
exposed to estrogen levels equivalent to about 100 years worth of hormone
replacement therapy.
Noting that nearly 50 years of research has failed to detect a significant
increase in the risk of breast cancer among women taking hormone replacement
therapy, Bush said, "It's time to put the baby to bed."
