Denise Grady / New York Times News Service

Should healthy women take drugs to lower their risk of breast cancer?

On Monday, an influential panel of experts said that the answer is yes, but only for certain women who are at increased risk because of breast cancer in the family or a personal history of breast lumps or other problems. Two drugs, tamoxifen and raloxifene, can lower the risk, and may be worth taking even though both can have serious adverse effects like blood clots and strokes, the experts said.

The panel, the U.S. Preventive Services Task Force, recommended that for healthy women ages 40 to 70, doctors help assess the odds of breast cancer and offer to prescribe one of the drugs for patients whose risk is above average — but only if their chances of developing blood clots and strokes is low.

Because of the adverse effects, the panel also advised that the drugs not be prescribed for women unless they are at increased risk of breast cancer.

“There is evidence of benefit for certain women,” said Dr. Wanda Nicholson, a task force member and an associate professor of obstetrics and gynecology at the University of North Carolina School of Medicine in Chapel Hill.

Nicholson said she recommended the drugs for some of her own higher-risk patients. Some take them; some choose not to.

“The take-home point for women is to have that initial conversation with their provider,” she said.

The task force recommendations are being published in draft form and are open for public comment until May 13. An analysis of research on which the recommendations were based was also being published in Annals of Internal Medicine. The advice matches that given by the task force in 2002 (the group re-evaluates many of its subjects once a decade), though the earlier report stopped short of telling doctors to offer to prescribe the drugs. Members of the group said they relied on a wealth of new data that helped confirm and clarify the risks and benefits of the two drugs, and how they measure up against one another.

Tamoxifen and raloxifene have been recommended for years for women whose odds of developing breast cancer are higher than average. Both drugs block the effects of estrogen and can lower the risk of the type of breast cancer whose growth is stimulated by the hormone. About 75 percent of breast cancers fall into that category.

Tamoxifen is more commonly used to prevent recurrences in women who have already had breast cancer, and raloxifene is most often prescribed to prevent fractures in women with osteoporosis. Tamoxifen can also lower the risk of fractures.

Doctors may see these drugs as a rare opportunity to lower the risk of cancer, but some women see them as simply trading one risk for another. Many healthy women, even if they are at increased risk, refuse the drugs, asking why they should take pills to lower the odds of a disease they may never get anyway, especially when the drugs can have dangerous or unpleasant side effects.

Besides increasing the risk of blood clots and strokes, the drugs can also cause hot flashes and vaginal problems that can ruin a woman’s sex life. In addition, tamoxifen can lead to cataracts and uterine cancer.

In the United States, 232,000 new cases of breast cancer are expected this year, and about 40,000 women will die from the disease.

The group estimated that among 1,000 women with an increased risk of breast cancer, there would be 23.5 cases of invasive breast cancer over five years. If the women took one of the drugs, seven to nine cases would be prevented over five years.

But an extra four to seven women per 1,000 taking the drugs would develop blood clots during that time, and there would be four extra cases of uterine cancer per 1,000 women taking tamoxifen — an approximate doubling of both of those risks.