Hormone Users Risk Cancer, Study Says
Women who take hormones after menopause face a greater risk of breast cancer than had been thought, and they are at risk regardless of which formulation they use, according to the largest study to examine the link.
The study, which involved more than one-quarter of all British women, found that those who take any hormones -- whether estrogen alone or in combination with progestin, and whether in pills, patches or gels -- are significantly more likely to get breast cancer than those who do not, and the risk goes up the longer women take the drugs.
The greatest risk, however, is clearly for women taking any combination of estrogen and progestin, which the study found doubles the risk for breast cancer. Women taking estrogen alone are 30% more likely to get breast cancer, compared with nonusers.
The findings mean that if 1,000 postmenopausal women in developed countries began taking hormones at age 50, there would be five extra cases of breast cancer among those taking estrogen alone and 19 extra cancers among those taking both hormones after 10 years. Based on those numbers, the researchers calculated that over a decade, hormone replacement therapy would cause an extra 10,000 cases of breast cancer in England among women ages 50 to 64, and an extra 100,000 cases in the United States.
“What we’ve shown is this huge, huge, highly significant increase in risk,” said Valerie Beral, a professor of epidemiology at the University of Oxford, who led the study. “We’ve really confirmed in an unequivocal way that estrogen and progestin combined has a much greater risk of breast cancer.”
The findings, published in Saturday’s issue of the journal Lancet, provide yet another reason for women to avoid the hormones, which millions had been taking for decades to alleviate hot flashes and other symptoms of menopause, as well as to protect their bones and hearts.
A U.S. study last year concluded that the risks from the hormones outweighed the benefits when it found that a combination of estrogen and progestin failed to protect the heart and appeared to increase the risk for heart attacks, strokes and life-threatening blood clots.
Earlier studies had shown hormones also increased the risk for breast cancer, but that risk was thought to be offset by the benefit to the heart and bones. The magnitude of the breast cancer risk had been unclear, along with whether the risk was posed by all formulations and all methods of taking them.
The new study, which analyzed data collected from 1,084,110 women ages 50 to 64, confirms and quantifies the breast cancer risk and extends the risk to all forms and types of hormone replacement therapy.
The decision to take hormones has always required a complicated weighing of risks against benefits. Women take progestin with estrogen to reduce the risk of uterine cancer from estrogen. But now that the addition of progestin has been shown to substantially increase the risk for breast cancer, that seems to offset the protective value against uterine cancer, said Marcia Stefanick of Stanford University.
