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New Study Links Hormones to Breast Cancer Risk
By LAWRENCE K. ALTMAN, New York Times August 8, 2003 A study of one million British women has found a higher death rate from breast cancer among those who took combination hormone therapy than those who did not use it or took estrogen alone. The study is by far the largest to determine the effects of hormones on breast cancer. The findings, which are being published in London on Saturday in the journal The Lancet, build on compelling evidence from studies in the United States that the risks of invasive breast cancer from combination hormone therapy were greater than many doctors had predicted. American experts not connected with the study said the new findings also strengthened recent recommendations against using long-term combination hormone therapy to prevent chronic conditions like bone fractures from osteoporosis. "This is a big study that generally supports everything we have said" about the risks of hormone therapy, said Dr. Rowan T. Chlebowski of the Research and Education Institute at Harbor-University of California at Los Angeles Medical Center in Torrance, Calif. He added that "it makes it harder for critics to argue that there was something wrong with" earlier studies, as some have done. Dr. Valerie Beral of Oxford University led the new study, which was paid for by the British government and Cancer Research UK, a charity, at an estimated cost of $10 million. The study involved about one-fourth of British women between the ages of 50 and 64 years. Women were invited to take part in the study at the time they were scheduled to have a regular mammogram. About half the women in the study took hormonal therapy. Women who took hormones at the time the study began in 1996 had a 66 percent increased risk of developing breast cancer and a 22 percent greater risk of dying from it by 2002. The risk of developing breast cancer was especially high for women taking an estrogen-progestin hormone combination, roughly double those of not taking hormones. For those taking only estrogen, the increased risk was 30 percent. The risks were about the same as found in earlier American studies, the experts interviewed said, but direct comparisons cannot be made because of differences in the ways the studies were designed. The risk of breast cancer increased over time. Dr. Beral's team calculated that after 10 years, there would be 5 additional breast cancers per 1,000 estrogen users and 19 additional cancers per 1,000 women who used an estrogen-progestin combination. That translated into 20,000 extra breast cancers among the women over the last 10 years; 15,000 of them were linked to combination therapy, and 5,000 to estrogen alone, the researchers said. No similar estimate has been made for the United States, experts said. Dr. Leslie G. Ford, an official of the National Cancer Institute, pointed to one finding she called "comforting." The risk for breast cancer declined gradually after women stopped hormone therapy; five years after quitting, women faced no greater risk than those who had never taken it. Conversely, said Dr. Marcia L. Stefanick of Stanford University, "It looks like the longer you use hormones, the worse off you are." Some proponents of hormone therapy have contended that using a patch to deliver hormones is safer than pills. But the British study found no evidence for that belief. Nor did the study find any links between breast cancer rates and other points of contention like the brands of hormones, the amount taken, and whether they were taken daily or in prescribed cycles. Dr. Ford, the National Cancer Institute official, said the British study supported findings reported in June suggesting that combination hormone therapy led to more aggressive cancers that were detected at a more advanced stage than among women who do not take such therapy. Combination therapy also increased the percentage of women with abnormal mammograms, according to the study that was published in the Journal of the American Medical Association. An editorial in the new issue of The Lancet said that long-term users of combination hormones should stop it as soon as possible, but that physicians should convey that message in a supportive way to avoid panic and over-reaction. The new study is not likely to settle questions about the safety of combining progestin and estrogen hormones for short-term use to treat hot flashes, night sweats, vaginal dryness and other symptoms that can plague women at menopause, the experts said. Questions about the proper drug regimens and length of treatment may not be resolved until an American study is completed in about two years. Dr. Beral's team conducted an observational study, a type that generally is not regarded as reliable as the gold standard, a randomized controlled trial. Still, American experts interviewed said they were impressed by the sheer size of the British study and its design. "It's a very powerful study," said Dr. Isaac Schiff, chief of obstetrics and gynecology at the Massachusetts General Hospital. Findings from the study indicate that the risk of breast cancer may increase long before five years, shrinking the window of safety, said Dr. Schiff who is also chairman of the American College of Obstetrics and Gynecology's hormone therapy task force. Dr. Chlebowski, the U.C.L.A. expert, said that "the fog is lifting" as different studies using different methodologies had come up with generally" similar findings. Many doctors and the drug industry promoted use of hormone therapy a
few years ago despite the lack of evidence from clinical trials. But now
experts say that experience has taught doctors and society a lesson in the
need to exert extreme caution in introducing new therapies. Copyright
© 2002 Global Action on Aging
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