In a new study of women at higher risk of breast cancer, few said they were willing to take the drug tamoxifen to prevent the disease.

Only about 18 percent of the 255 women surveyed said they were inclined to take tamoxifen, says the study in Cancer's May 15 edition.

The women expressed their opinions after being informed about tamoxifen's risks and benefits. Possible side effects were the most commonly cited concern. The results weren't affected by the women's perceptions about their breast cancer risk.

"The current results indicate that many high-risk women are unwilling to consider tamoxifen even with extensive education about its potential benefits and harms," write the researchers, who included Joy Melnikow, MD, MPH, of the University of California-Davis.

About Tamoxifen

Tamoxifen is a commonly prescribed medication for treating breast cancer. It's also used to help prevent breast cancer in women at high risk for the disease.

Tamoxifen blocks estrogen, a hormone that causes many breast cancers to grow.

Side effects include an increased risk of uterine cancer and blood clots, a small increase in the risk of stroke, and hot flashes.

On the other hand, tamoxifen helps prevent osteoporosis in women who've gone through menopause.

The FDA approved tamoxifen to reduce the risk of breast cancer in 1998, but the drug's use for that reason has been "controversial," write Melnikow and colleagues.

About 2 million U.S. women would experience a net benefit from taking tamoxifen, they say. But only an estimated 5% of tamoxifen sales by AstraZeneca — the drug's maker — are for the reduction of breast cancer risk, Melnikow notes.

Surveying Women's Opinions

Participants were 255 women at higher risk for breast cancer. None had developed breast cancer before.

Most of the women's breast cancer risk factors included being at least 50 years old. However, some women younger than this were included in the study. Other risk factors evaluated were race, age at first period, age at first live birth, family history, and history of previous breast biopsies.

First, the women got a 15-minute presentation on tamoxifen's pros and cons. Next, they answered questions about their views on tamoxifen.

After the presentation, 18 percent of the women said they were inclined to take tamoxifen to lower their breast cancer risk. Participants with the highest breast cancer risk were no more likely to opt for tamoxifen than others.

What Mattered Most

More than half of the women said the following benefits and risks were "very important" in their decision:

—Fighting breast cancer: 69 percent

—Blood clot in the lung (pulmonary embolism): 68 percent

—Uterine cancer: 63 percent (among those who had not had a hysterectomy)

—Blood clots in the legs (deep vein thrombosis): 58 percent

About 15 percent said it would be difficult or very difficult to decide whether to take tamoxifen.

Cancer prevention drugs "must have few potential adverse effects to achieve widespread acceptance," the researchers conclude.

Trying Other Strategies

Some women said they weren't doing anything special to prevent breast cancer. But others mentioned doctor visits for breast exams and mammograms, as well as exercise and changes in diet (reducing or eliminating alcohol and caffeine). Also mentioned was reducing or stopping the use of tobacco.

Overall, the women seemed to weigh their perceived risk factors against their personal prevention strategies, sizing up their susceptibility before deciding about tamoxifen, says the study.

Exaggerated Sense of Risk

Another trend also stood out. The women tended to overestimate their breast cancer risk, sometimes rating it 10 times higher than it actually was.

Women's average self-perceived risk of developing breast cancer in the next five years was almost 33 percent. But the calculations by the Breast Cancer Risk Assessment Program put it at about 3 percent.

Despite the inflated sense of risk, about 70 percent described their risk as "low" or "average."

See a Doctor for Questions

It's important for women to see a doctor about any breast concerns and to follow recommended screening guidelines, whether or not they think they're at high risk.

Early detection improves a woman's chances of survival. There are more than 2 million breast cancer survivors in the U.S., says the American Cancer Society (ACS).

Breast cancer is the most common cancer among women after skin cancer and the leading cause of women's cancer deaths after lung cancer, says the ACS.

By Miranda Hitti, reviewed by Michael W. Smith, MD

SOURCES: Melnikow, J. Cancer, May 15, 2005; vol 103. News release, John Wiley & Sons, Inc. WebMD Medical Reference from Healthwise: "Tamoxifen."