Published April 22, 2013 By Dr. Susan Love

The U.S. Preventive Services Task Force has released its draft recommendations regarding the use of medications for breast cancer risk reduction. (Note that it is a draft and you can both read and comment on it here.)

The drugs in question are tamoxifen and raloxifene, both of which have been shown in randomized controlled studies of high-risk women to reduce the risk of developing estrogen positive breast cancer. Tamoxifen, a breast cancer treatment, can be used by both pre- and postmenopausal women. Raloxifene (Evista) a drug initially developed to reduce risk for osteoporosis, is only approved for use by postmenopausal women.

If this seems like old news to you, you are right. There is no new data regarding these drugs just a longer history of their use. So why is the USPSTF changing its view?

Well, it’s complicated. While we tend to overdo treatment for breast cancer in this country, we are also less likely to use drugs to prevent it. One study estimates that about 19 percent of white women, 6 percent of African-American women, and 3 percent of Latinas are high risk and might benefit from taking these drugs. Currently, though, less than 1 percent actually do.

It’s not just because of the cost. Part of the problem is that doctors aren’t routinely recommending these medications to their high-risk patients—and the USPSTF is hoping that its new recommendations will change this. But another is the side effects of the drugs. Only about half of all women who have been diagnosed with breast cancer stay on their hormone therapy for the full five years. And if women who have breast cancer don’t see the side effects as worth the benefit, it’s easy to understand why someone who is advised to take them for prevention might not either.

Are there women who should be taking tamoxifen or raloxifene to prevent breast cancer? That, too, is a complicated question, as it depends on a woman’s risk. If your risk of getting the disease is at the high end of the spectrum, you will benefit more than someone who is at the low end. But even this is complicated by the fact that women who have a BRCA genetic mutation, and are really high risk, are more likely to develop estrogen receptor negative breast cancer—and tamoxifen and raloxifene reduce only the risk of estrogen-receptor positive tumors.

This means that women and their doctors have to weigh the risks and benefits in individual cases. The drugs are probably of most use in women who have been diagnosed with atypical hyperplasia on a breast biopsy as they have the most to gain. But risks need to be considered. And these drugs do have risks. Tamoxifen increases the risk of blood clots (4-7 cases per 1,000 women over 5 years) as well as uterine cancer (4 cases per 1,000 women), and cataracts. Raloxifene and tamoxifen may also increase the risk for stroke.

On the other hand, because both drugs build bone, they could offer benefits to women who have low bone density. Moreover, if you are high risk and don’t have a uterus, then the benefit of tamoxifen goes up because you don’t have to worry about its associated increased risk of uterine cancer. If you need to take a drug for osteoporosis and are high risk for breast cancer then you may also benefit from either of these drugs.

So what is the bottom line? It is not uncommon for a woman to take drugs to prevent heart attacks (statins), strokes (drugs that reduce blood thinning and clotting) and fractures (bisphosphonates). So, the idea that someone would take a drug to reduce a health risk is not new.

You can calculate your breast cancer risk here to see if you are someone who possibly could benefit from tamoxifen or raloxifene. The USPSTF suggests that if you are a woman with a risk of at least 3% over the next five years that you discuss chemoprevention with your doctor. Ultimately, though, whether you decide to take tamoxifen or raloxifene to reduce your breast cancer risk is up to you!

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