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Drugs Can Cut Breast Cancer Risk for Some: Experts

Draft guidelines for doctors reflect findings, but it's hard to know who will benefit most, experts say

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In addition, "some women have side effects that are not life-threatening but they are uncomfortable and not minor, and cause them to stop medications, such as vaginal discharge, dryness, itching, leg cramps," Nelson explained.

Tamoxifen is currently approved by the U.S. Food and Drug Administration to reduce the risk of breast cancer among women at increased risk who are 35 years and older, whereas raloxifene is only approved for this use in postmenopausal women.

These medications are taken as a once-a-day pill and women are recommended to take them for five years, Nelson said. Raloxifene is also approved to prevent or treat osteoporosis, and for those uses women take the medication for a longer period of time, she noted.

Despite the fact that these medications have been available for a long time -- tamoxifen was approved for breast cancer chemoprevention in 1998 -- studies suggest they are underused. Only 60,000 women in the United States used tamoxifen in 2005, down from 120,000 in 2000, even though at least 2 million could be eligible for it.

Part of the problem could be that it is difficult for doctors to predict which patients are at high risk for developing breast cancer, Nelson explained. The FDA uses a risk assessment tool called the Gail model, which takes into consideration age, race, medical history and other factors, to define a woman's risk level, but even this model is not necessarily a good predictor for an individual patient, Nelson said.

The most important factors for determining risk of developing breast cancer are increased age, family history and having had a biopsy that showed signs of precancers, Nelson said.

One expert said he expected the report to stimulate a new look at this use of these medications.

"These drugs work, this is an effective chemoprevention regimen," said Robert Smith, senior director of cancer screening at the American Cancer Society in Atlanta.

Another reason that these drugs could be underused is that, as women age, they are more likely to see an internist or primary care physician than a gynecologist, and these types of doctors could be less likely to have a conversation about breast cancer chemoprevention, Smith said.

"The task force update is likely to stimulate some action among primary care physicians," Smith said.

Even though patients' concerns about side effects could also factor into the underuse of tamoxifen and raloxifene, most women do decide to take one of the drugs if their doctors recommend it, Smith said. The current report found that 70 percent of women took the recommended treatment dose.

The adverse effects of blood clots, endometrial cancer and cataracts are less likely if women take these drugs at a relatively young age, Nelson said. However, the risks might be too high for women who have a history of blood clots or cataracts, she added.

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