fb-pixel Skip to main content

Why do few high-risk women take drugs to prevent breast cancer?

With little fanfare and scant media coverage, a government task force recommended on Monday that women at high risk of breast cancer consider taking drugs to prevent the disease. The primary care physicians on the panel reaffirmed their previous recommendations made back in 2002, but few high-risk women have opted to take the estrogen-blocking medications -- either tamoxifen or raloxifene -- and I’m guessing very few will likely do so in the future.

But more of them should try the drugs, according to the draft guidelines issued by the US Preventive Services Task Force on Monday, because the benefits outweigh the risks.


“A fairly small percentage of women who have a net benefit actually do end up taking one of these drugs,” said Dr. Mark Ebell, an associate professor of epidemiology at the University of Georgia College of Public Health who co-authored the new guidelines. “We think it’s important for women to consider their options.”

To be clear, the task force comes out against the routine use of prevention medications in those at average risk of breast cancer.

The drugs are recommended only for those at increased likelihood of getting breast cancer because of certain factors calculated on this risk assessment tool: family history, previous benign breast biopsies, first childbirth later in life, and early menstruation.

Women who have a 3 percent or greater breast cancer risk over the next five years would benefit from taking a prevention drug. A 50-year-old woman who started menstruating at age 11, has a mother with breast cancer, and had two previous breast biopsies would fall into this category.

For women who carry one of the known BRCA gene mutations, which put them at much greater increased risk, the task force has a separate set of guidelines for prevention that may include prophylactic mastectomies or annual MRI screenings.


In reaffirming its previous recommendations, the task force did a review of the latest research and found even stronger evidence that tamoxifen works well to prevent breast cancers that are driven by the female hormone estrogen. Studies lasting up to seven years found that using tamoxifen prevented about half of breast cancers in this high-risk group, decreasing their chances of developing breast cancer from 4 percent to 2 percent, according to Ebell.

None of the studies has demonstrated that these drugs reduce breast cancer deaths, however, but Ebell said that might be because the studies haven’t continued long enough or been large enough to measure this impact.

The drug raloxifene led to smaller reductions in breast cancer risk but was also less likely to be associated with side effects such as endometrial cancer, cataracts, and blood clots.

The task force said high-risk women who haven’t had a hysterectomy should usually take raloxifene, rather than tamoxifen, to lower their risk of endometrial cancer, which occurs in the uterine lining. Those who have had a hysterectomy to remove their uterus are generally better off taking tamoxifen to get the bigger breast-cancer prevention benefit.

Hot flashes may be the biggest drawback to taking either of the two drugs, because they’re quite common and can dramatically interfere with a woman’s quality of life. The sudden flush of warmth and sweating occurs in about half of women who take these drugs for prevention, even in those who are years past menopause.


“A lot of people find the hot flashes off-putting,” said Dr. Judy Garber, director of cancer prevention at the Dana-Farber Cancer Center. “Many women won’t have any, but they may need to try the drugs to see how they do.”

But women at increased breast cancer risk typically don’t even want to try the drugs short-term, which I can’t understand since surveys suggest that breast cancer is the disease women fear most.

Garber told me she thinks women opt against the medications after hearing about the possible side effects. “People in general are more skeptical of medication safety,” she said, “and often want to take a natural approach, like an herbal supplement, even if there’s no evidence that it works.”

What's more disturbing, though, is the trend toward doing bilateral mastectomies for prevention. While these may be warranted for those with BRCA gene mutations, some women without a BRCA mutation ask for the surgery -- after having several benign breast biopsies --because they don’t want frequent monitoring or to live in constant fear of getting breast cancer.

“Women at increased breast-cancer risk need to take the time to make a careful decision about what to do for prevention,” Garber said. “But the prophylactic mastectomy is an irreversible step compared to medication, which they can stop.”

Deborah Kotz can be reached at dkotz@globe.com. Follow her on Twitter @debkotz2.