BETHESDA, MarylandResearchers abruptly halted a prevention trial of
estrogen/ progestin in healthy menopausal women after an independent monitoring
committee found a 26% increase in invasive breast cancer among women taking the
hormone replacement therapy (HRT). The committee also found that the HRT group
had a greater risk of coronary heart disease, stroke, and pulmonary embolism
than the placebo group.
The National Heart, Lung, and Blood Institute (NHLBI) stopped the trial,
which is a component of the Women’s Health Initiative (WHI), after 5.2 years
of average follow-up. The study was scheduled to run until 2005. It was
designed to determine whether postmenopausal estrogen/progestin therapy, given
to women with a uterus, could prevent heart disease and hip fractures and to
determine its risks.
The study involved 16,608 women ages 50 to 79 who were randomized to receive
placebo or 0.625 mg of conjugated equine estrogens plus 2.5 mg of
"The cardiovascular and cancer risks of estrogen plus progestin
outweigh any benefits, and a 26% increase in breast cancer risk is too high a
price to pay, even if there were a heart benefit," said NHLBI director
Claude Lenfant, MD.
On the positive side, the WHI results show a 37% reduction in colorectal
cancer in the treatment group, a 24% decline in hip fractures, and no
difference in mortality from all causes.
A separate WHI study of estrogen-only in women who have had a hysterectomy
is continuing because the risks and benefits of estrogen alone remain
undetermined. According to the data safety and monitoring board, there is no
indication of any increased breast cancer risk in the estrogen-only study.
"When the estrogen-only trial is completed, a comparison of the results
of these two trials may provide a better idea of the role of estrogen vs
estrogen/ progestin, in health and disease," said Marcia Stefanick, PhD,
associate professor of medicine, Stanford University, and chair of the WHI