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Tropic of Cancer 
The news on breast-cancer research that could save lives
2/18/2002 |
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Estrogen
It may be an elixir of youth, but is there a risk of cancer?
6/26/1995 |
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Biology, alas, is rarely so straightforward. Researchers came to realize that it wasn't safe to give estrogen alone to a woman with an intact uterus. Unopposed estrogen, as it is called, dramatically increases the chances that a woman will develop uterine cancer. (Obviously, this isn't a problem for women who have undergone hysterectomies.) The addition of progestin, another female hormone, seemed to take care of that problem.
The conviction that long-term HRT was beneficial became so entrenched that doctors who delved into the issue more closely were surprised to discover how thin the evidence was. In the early 1990s, Dr. Deborah Grady of the University of California at San Diego was asked to help write guidelines on HRT use for the American College of Physicians. She remembers growing increasingly uncomfortable as she sifted through the scientific literature. None of the studies were definitive. Most were observational studies that showed that women who took HRT lived longer and with fewer health problems than those who didn't. Perhaps HRT was the real reason, or perhaps women on HRT were simply more health conscious than their counterparts. No one could say for sure.
Even the studies that showed that estrogen improved a woman's cholesterol profile weren't ultimately all that satisfying. After all, plenty of women with normal cholesterol levels still have heart attacks. What was needed was a hard-core clinical trial so rigorously designed that no one could contest the results.
Former U.S. Congresswoman Pat Schroeder remembers arguing for such studies. At the end of the 1970s, she recalls, the largest study done by the National Institute on Aging "didn't have one woman in it. They didn't know anything about osteoporosis, menopause, anything. They wouldn't do anything for women but throw pills at us." With a shove from Schroeder, other female legislators and women's groups, the WHI was launched in 1991. The giant investigation was designed to get some precise answers to the hormone debate and determine the best strategies for preventing the diseases of aging, including heart disease, cancer and osteoporosis.
Some Answers at Last
More than 160,000 American women are enrolled in the WHI, which is divided into five major studies that look at everything from the role of diet in determining a woman's health as she ages to the role of hormones in that process. More than 16,000 healthy women, ages 50 to 79, volunteered for the study on estrogen and progestin.
Half of these women were randomly assigned to receive the hormone combination, and the other half were given a placebo, or dummy pill. Neither the women nor their doctors knew who was taking the active medication. This type of study, called a double-blind, randomized, controlled trial, is the most rigorous type of investigation scientists know how to conduct. It's a long, difficult path to take to get an answer, but at least you can be certain of the results.
The plan was to follow the women for an average of eight years and record how many suffered from heart attacks, strokes, blood clots, hip fractures or colon cancer. From the outset, a safety board monitored the data to ensure that the study would be stopped before its scheduled ending in 2005 if there was evidence of such a clear benefit that it would be unethical to withhold the drug treatment from those women in the control group. It would also be stopped if, conversely, the risks of HRT so obviously outweighed the benefits that women in the treatment group should stop taking the drugs.
The first hint that all was not well came late in 1999, when the monitoring board detected an unexpected increase in the risk of blood clots and heart attacks in women on combination-hormone therapy. Although the absolute risk was small, it came as a shock. Most doctors believed that hormone replacement offered protection against cardiovascular disease. Investigators informed participants and their doctors of their findings early in 2000 but decided to continue the study to see if the negative effect persisted. Perhaps, they reasoned, it takes longer for cardiovascular benefits to appear.
By the spring of this year, however, a new danger emerged from the data. Not only were women who took estrogen and progestin more likely to suffer heart attacks and blood clots in the lungs and legs, but they also had a slightly increased risk of developing breast cancer. That was just enough to tip the scale. Though the women on HRT suffered fewer hip fractures (1 woman per 1,000 per year vs. 11/2 women per 1,000 per year), the benefit wasn't great enough to warrant the risk. Because the trial was designed to look at women who were already healthy, the safety bar was set fairly high. Given the criteria that the monitoring board had developed before the WHI study began, this part had to be stopped.
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