Know Your Options for Breast Cancer Prevention

Preventive drugs for high-risk, postmenopausal women
Know Your Options for Breast Cancer Prevention

By: Holly Pederson, MD

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When we talk about drugs for breast cancer, we often focus on medications used for treatment after a diagnosis.

But medications can play a major role in prevention, too.

There are more than 2 million postmenopausal women in this country who are healthy but who have an elevated risk of breast cancer. These women should know they have options.

“Postmenopausal women who are healthy but have a high risk of breast cancer now have four preventive medications available.”

The most recent option for prevention

In a 2013 prevention trial in the United Kingdom, researchers followed 3,864 postmenopausal women who were at high risk for breast cancer, either because of family history or other factors. The researchers gave these women either anastrozole (Arimidex) or a placebo daily for five years.

The results showed a 53 percent reduction in risk in the group that received anastrozole compared with the placebo group. After five years, 2 percent of women on anastrozole had developed breast cancer, while 4 percent of those on a placebo had.

But preventive medications are not a new concept. Anastrozole is just the most recent option to emerge for high-risk women.

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Four options for high-risk cases

Two other medications, tamoxifen and raloxifene, have been in use for years. Both drugs are selective estrogen receptor modulators (SERMs). SERMs work by blocking the estrogen receptors in a woman’s breasts.

Trials on both medications showed around a 50 percent reduction in the risk of ER-positive breast cancer, the most common type of breast cancer. This type depends on estrogen to grow.

More recently, another drug made the list: exemestane. Exemestane showed an even higher risk reduction at 65 percent. It’s called an aromatase inhibitor. Aromatase inhibitors work by blocking an enzyme that leads to estrogen production.

Anastrozole is also an aromatase inhibitor. Based on promising clinical trial results, we expect future inclusion in clinical guidelines for the prevention of breast cancer, much like exemestane. National Comprehensive Cancer Network risk reduction guidelines include both drugs for consideration for risk reduction in postmenopausal women. But at this time neither has been FDA-approved for this use.

The bottom line: Postmenopausal women who are healthy but have a high risk of breast cancer now have four preventive medications available.

Starting the discussion

We believe all postmenopausal women who are at high risk of breast cancer should be aware of these promising preventive medications.

However, no drug is perfect. Side effects are a concern. For example, tamoxifen can increase the risk of uterine cancer or endometrial polyps. Both tamoxifen and raloxifene come with a slight risk of blood clots, as well.

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Exemestane and anastrozole don’t come with the same blood clot risk, but they do both increase the risk of joint pain and come with a slight reduction in bone density. And all four of these drugs can make hot flashes, night sweats and vaginal dryness worse — valid concerns for postmenopausal women.

That’s why we often recommend a trial run, and we pick the best option based on a woman’s individual case. We recommend a 5-year course of these medications if they are well-tolerated; that’s the typical length of time studied in clinical trials.

These medications won’t be right for everyone. But high-risk postmenopausal women deserve the opportunity to discuss them with their doctors, to weigh the pros and cons, and to come to an informed decision.

At the least, they deserve to know that preventive options are available — and that those options are growing in number.

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