Should healthy women take drugs to lower their risk of breast cancer?
On Monday, an influential panel of experts said 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 Wanda K. 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.
Dr. 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 is also being published Monday in Annals of Internal Medicine.
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.
The task force considered a woman likely to benefit from the drugs if her odds of developing breast cancer during the next five years were 3 percent or higher.
One common method of estimating the risk uses an online tool that asks a series of questions about the patient's age and her personal and family medical history. It then calculates an estimated risk, and compares it to the average for women of that age.
According to this method, at age 40 the average woman has a 0.6 percent risk of developing breast cancer over the next five years; at age 50, 1.3 percent; at age 60, 1.8 percent; at age 70, 2.2 percent. Plugging risk factors into the calculator, like mothers or sisters with breast cancer, or a personal history of breast biopsies, even benign ones, makes the risk go up.
But experts warn that although these estimates can be useful in predicting the risk for large populations of women, they do not work very well for individuals.
The report from the task force states: "Most women identified as 'high risk' will not develop breast cancer, and the majority of breast cancer cases will arise in women who are not identified as having increased risk." The group also noted that the type of risk calculator generally used is not recommended for women who are known or suspected to have mutations in BRCA genes, which greatly increase the risk of breast cancer.