New Guidelines: Breast Cancer Prevention Drugs

Healthy women who have known risk factors for developing breast cancer should talk to their doctor about taking medication to prevent the disease, says a new recommendation from a national panel of health experts.

The new guidelines from the U.S. Preventive Services Task Force (USPSTF) recommend that clinicians consider prescribing tamoxifen (Soltamox), raloxifene (Evista), or aromatase inhibitors to women age 35 and up who are at higher than average risk for breast cancer.

What degree of risk warrants preventive medication must be determined by a woman and her doctor. Among the factors that will be considered include family history, genetics, and whether you have dense breast tissue.

New Guidelines Add Another Category of Drugs to the Options

The new recommendations — which were published last month in the Journal of the American Medical Association and on the USPSTF website — update a similar version published in 2013.

They differ in that they now include an additional class of medication, aromatase inhibitors, on the list of drugs believed to help reduce women’s risk. (Aromatase inhibitors have not yet been approved by the Food and Drug Administration specifically for the purpose of preventing breast cancer.)

Although their particular mechanisms vary, the breast cancer medicines recommended by the task force all work by lowering or blocking estrogen — a female hormone — to decrease breast cancer risk. The medication must be taken daily for a period of five years.

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A Track Record of Reducing Risk

In 10 trials reviewed by the task force, all three types of drugs reduced invasive and ER-positive breast cancer but not ER-negative breast cancer. “If 1,000 women at higher risk took these medications for five years, you’d expect somewhere between 7 and 16 fewer cases of breast cancer,” says task force member Michael Barry, MD, medical director of the John D. Stoeckle Center for Primary Care Innovation at Massachusetts General Hospital in Boston.

“Again, that’s out of 1,000, so it may seem like a small number,” he says. “But of course if you’re one of those women, it might be quite important.”

The Challenge of Determining a Woman’s Breast Cancer Risk

The USPSTF stresses that the medication should be considered only for women whose odds of developing breast cancer are higher than average — but determining those odds is not always easy.

Widely available risk-assessment models such as the Gail model, the first used clinically, weigh factors including (but not limited to) a woman’s age, whether she has first-degree relatives with breast cancer, and how old she was when she first got her period.

But such tools are imperfect, and there is no single definition for what constitutes being at higher risk, according to the American Cancer Society.

“Although there are a lot of models, they are very rough guidelines,” says Leif W. Ellisen, MD, PhD, program director of Breast Medical Oncology at Massachusetts General Hospital Cancer Center in Boston, who was not a member of the task force. “That’s challenge number one.”

According to Dr. Ellisen, the second challenge for primary care providers is analyzing potential risk versus benefits of these medicines. “If we say, ‘Well, this could cut your risk for breast cancer in half if you just take the medicine for five years,’ that sounds pretty good. But if the woman’s risk is already quite low, it may not be very meaningful.”

What’s more, the medication is not without side effects. Mild side effects include hot flashes, fatigue, and mood swings. More serious ones may include blood clots and other forms of cancer.

Primary Care Physicians Often Don’t Suggest the Drugs

Many women who are at increased risk may never learn about the option of taking preventive medication. The task force notes that only 10 to 30 percent of primary care doctors say they have prescribed breast cancer prevention medication. And most of those say they have done so only a handful of times.

“I do think most women have never heard of these,” says Mary B. Daly, MD, PhD, a professor in the department of clinical genetics at the Fox Chase Cancer Center in Philadelphia, who was not a member of the task force. “And I think prescribing them has never really been in the realm of primary care.”

Dr. Daly advises patients with a family history of breast cancer to mention this to their doctors during the context of family history. Similarly, if a woman is concerned about other risk factors, such as dense breasts, she should mention it.

“If their primary care doctor doesn’t feel comfortable discussing these [medications], a referral to a breast cancer risk specialist is indicated,” says Ellisen.

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