If news reports about the risks of taking estrogen make you confused, you're not alone. Headlines like these have blazed across the country:

"Study Links Estrogen Supplements, Ovarian Cancer"

"Hormone-Breast Cancer Link Found in Study Downplayed"

"Cancer Link Contradicted by New Hormone Study"

Deciding whether to take estrogen after menopause is difficult enough-these headlines certainly don't help.

But do these studies really show that taking estrogen creates a serious risk of getting breast cancer or ovarian cancer? No, they don't.

Ovarian cancer and estrogen

In the ovarian cancer study, American Cancer Society researchers started with almost 700,000 women and then excluded almost two-thirds of those women-including those who had cancer or their ovaries removed.

After seven years the researchers found that, out of the remaining 240,073 peri- and postmenopausal women, 436 women (0.2 percent) had died from ovarian cancer. Among the women who died, about 32 percent had taken estrogen replacement therapy. Further, the study concluded that women taking estrogen for six years or more had a 40 percent greater risk of ding from ovarian cancer; women taking estrogen for at least 11 years had a 70 percent greater risk.

But the researchers emphasized that they had not investigated whether estrogen increased a woman's risk of getting ovarian cancer, they just examined whether estrogen increased the risk of dying from ovarian cancer-a confusing distinction. Ovarian cancer is a rare disease, but its survival rates are low.

Breast cancer and estrogen

In the breast cancer study, Harvard Medical School researchers studied 122,000 nurses for 15 years. The researchers found that the women using hormone replacement therapy (estrogen and progestin) for five years or more after menopause (average ages 50-55 years) had a 30-40 percent greater risk of developing breast cancer than women who never used HRT. Among older women, who already have a greater breast cancer risk, the increased risk from HRT was 70 percent.

Breast cancer is the most common cancer among women, but 75 percent of those cases occur in women over age 64.

Asking the experts

So what do women's health experts think of these studies?

"This one was flawed by excluding two-thirds of the subjects," says Daniel Mishell, M.D., of the ovarian cancer study. Dr. Mishell is professor and chairman of the department of obstetrics and gynecology at the University of Southern California School of Medicine in Los Angeles.

"Someone once told me, `Never believe the results of a single epidemiological study,"' he observes. "I'm not going to take the results of one paper and talk to patients about it. I want a body of evidence." When he reviewed 10 previous studies, he found that some showed a protective effect, some showed no effect, and some showed an increased risk. "When you look at the rest of the literature, there's nothing to support this study," he concludes.

Putting it in perspective

Katherine Miller Bass, M.D., M.H.S., an assistant professor of obstetrics and gynecology at Johns Hopkins School of Medicine in Baltimore, sees one problem in the ovarian cancer study: it eliminated over 100,000 women who had undergone a hysterectomy.

"Women who've had a hysterectomy are at less risk of getting ovarian cancer," explains Dr. Bass, who is also an epidemiologist and reproductive endocrinologist. "So they've selected out all those people who might have less risk."

She recently completed a paper, with epidemiologist Dr. Trudy L. Bush, also of Johns Hopkins, that looked at the epidemiology and feasibility of screening for ovarian cancer. Dr. Bass's review of the literature showed no clear relationship between ovarian cancer and hormone replacement therapy.

"Certainly, if you have someone with a history of familial ovarian cancer, maybe she's not a good person to give hormone replacement therapy," she adds. "But for most people, the risk of developing ovarian cancer is very, very low."

As for the Harvard breast cancer study, when that came out, "I thought I would lose my mind," she says. "The phones were ringing off the hook in the office; I hardly saw a patient who didn't talk about this."

What did she tell her patients?

"I said, `This is not a new finding, this controversial information about breast cancer has been floating around for a while-and we do not have a definitive answer,"' she says.

On the other hand, when researchers looked at the relationship between estrogen and endometrial cancer, within 10 years the studies proved that unopposed estrogen can cause endometrial cancer-"it was very obvious," she notes.

Dr. Bass's personal opinion is that taking estrogen does slightly increase the risk for breast cancer. But does she think that risk outweighs the benefits?

"No," she states-the reality- is women are 10 times more likely to die of heart disease than breast cancer. "For most women, the risk (of breast cancer) does not outweigh the benefits of hormone replacement therapy for heart disease."

NOTE: In a study published in The Journal of the American Medical Association, researchers from the University of Washington compared about 500 healthy women with some 500 women newly diagnosed with breast cancer (all women aged 50-64). More than half of each group were taking hormone replacement therapy. Researchers found that the women taking HRT did not have an increased risk of breast cancer-further, the women taking HRT for more than eight years had less risk than women not taking HRT.

Estrogen's role in delaying onset of Alzheimer's

Estrogen's protective effects against heart disease and osteoporosis often carry significant weight in women's decisions about HRT. Now there's another reason to take into consideration when you're talking with your doctor about whether HRT is right for you: the role of estrogen in delaying the onset of Alzheimer's disease and lowering overall risk of the disease.

A study published in the British medical journal The Lancet followed 1,124 American women over a period ranging from one to five years. Among these women, 156 had used estrogen after menopause and 968 had not. Here is what the stud- revealed:

• The age at onset of Alzheimer's disease was significantly- later in women who had taken estrogen than in those who did not.
• The relative risk of the disease was significantly reduced in estrogen users vs. non-users.
• Women who had used estrogen for longer than one year had a greater reduction in risk.
• The study reinforces what is known about estrogen's effects on the brain, which include:
• increasing cerebral blood flow.
• promoting growth of new dendrites between cells. Dendrites conduct cell impulses.
• increasing the production of a brain enzyme that regulates memory and perception.
• inhibiting enzymes that break down neurotransmitters like serotonin, dopamine and norepinephrine.

"The Lancet article helps to explain differing rates of dementia in males and females of the same age," says Dr. Elizabeth Lee Vliet. "Scientists have observed [the difference] but without understanding why it was there. The hormonal connection is crucial."

While researchers stop short of saying that estrogen prevents Alzheimer's disease, the study sheds important light on the relationship between our hormone levels and brain function.

For more information: Effect of estrogen during menopause on risk and age at onset of Alzheimer's disease. by- Ming-Xin Tang, et al. The Lancet 1996: 348: 429-32.

Estrogen and healthy bowels

Two studies show that women taking estrogen have almost 50 percent less risk of developing and dying from colon cancer than women who have never taken estrogen.

Colon cancer doesn't get much press coverage, but it's the second most common cause of cancer deaths in the United States. An estimated 51,000 women will develop colon cancer each year, and almost half of those women will die from it.

Preventing colon cancer?

"The study provides more information for women and their physicians, to address the uncertainty-about the benefits and risks of (estrogen) therapy-," says Polly A. Newcomb, Ph.D., a cancer epidemiologist and coauthor of a University of Wisconsin study that looked at women's risk of developing colon cancer.

"It's pretty clear that hormone replacement therapy decreases the acute effects of menopause, it probably decreases bone loss, and it very likely decreases coronary heart disease. And I would say that it also very likely decreases the risk of developing colon cancer," Newcomb states.

"The strongest effect appeared to be among women who had used hormone replacement therapy recently (within the past 10 years), rather than if they had just ever used it any time in their lives." Further, the longer women took estrogen, the more they were protected.

Newcomb's study was also able to look at some lifestyle factors and found that colon cancer risk was greater for heavier women, for women with a family history of colon cancer, and for women who drank large amounts (two or more drinks a day) of liquor. Women who drank two or more beers a day had an increased risk of rectal cancer.

A new role for estrogen?

"I don't think anybody has thought of estrogen as a preventive in terms of cancer," notes Eugenia E. Calle, Ph.D., director of analytical epidemiology at the American Cancer Society. Cane was lead author of the other colon cancer study, which found that estrogen halved women's risk of dying from colon cancer.

Right now, no one knows how estrogen protects the colon. Researchers speculate that estrogen replacement may reduce bile acids in the colon, which have been shown to promote colon cancer in animals. Or estrogen may protect the lining of the colon or actually inhibit the growth of colon cancer cells.

"We need to know what the mechanism might be," Calle states. In particular, the fact that both studies found a dose response with years of use-meaning the longer women took estrogen the more protected they were-had a big impact.

Two lines of research need to be pursued: more epidemiologic studies and more biologic mechanism studies, Calle observes. "Are we looking at something that just influences whether polyps turn into tumors or are we talking about something that influences polyp formation in the first place? There's just a lot of work that needs to be done."