Clinicians should discuss medications for breast cancer that can help women at increased risk for the disease, but such medications should not be used by women who are not at increased risk.

These new recommendations from the U.S. Preventive Services Task Force (USPSTF), presented in a document entitled Medications for Risk Reduction of Primary Breast Cancer in Women, reaffirm the group’s 2002 guidance. That year, the USPSTF issued a “B” recommendation for clinicians to discuss risk-reducing medications with women at high risk for breast cancer and at low risk for adverse effects from medication. As in 2002, the 2013 update again received a B grade, which indicates the USPSTF’s high certainty that the net benefit of the recommended service is moderate or moderate certainty that the net benefit is moderate to substantial.

Specifically, the updated recommendation states that clinicians should engage in shared, informed decision-making with women who are at increased risk for breast cancer about medications to reduce their risk. For women who carry that heightened risk but who are at low risk for medication side effects, clinicians should offer to prescribe tamoxifen, raloxifene, or other risk-reducing agents.

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The recommendation applies to asymptomatic women aged 35 years and older without a prior diagnosis of breast cancer, ductal carcinoma in situ, or lobular carcinoma in situ. The USPSTF noted that important risk factors for breast cancer include increasing age, family history of breast or ovarian cancer (particularly among first-degree relatives and onset before age 50 years), history of atypical hyperplasia or other nonmalignant high-risk breast lesions, previous breast biopsy, and extremely dense breast tissue.

Neither tamoxifen nor raloxifene should be used in women who have a history of thromboembolic events (deep venous thrombosis, pulmonary embolus, stroke, or transient ischemic attack). And, just as it did in 2002, the USPSTF recommended against the routine use of tamoxifen, raloxifene, and other drugs for risk reduction of primary breast cancer in women who are not at increased risk for the disease.

In the information reviewed to inform the updated recommendations, the USPSTF found adequate evidence that treatment with tamoxifen or raloxifene can significantly reduce the relative risk for invasive estrogen receptor (ER)-positive breast cancer in postmenopausal women who are at increased risk for the disease. A systematic review of clinical trials demonstrated that tamoxifen and raloxifene reduced the incidence of invasive breast cancer by 7 to 9 events per 1,000 women over 5 years, and that tamoxifen reduced breast cancer incidence more than raloxifene did. In addition, the USPSTF reported that tamoxifen also reduces the incidence of invasive breast cancer in premenopausal women who are at increased risk for the disease.

The evidence indicated that, in general, women with an estimated 5-year risk for breast cancer of 3% or greater are, on the basis of model estimates, more likely than other women to benefit from tamoxifen or raloxifene. Women who are not at increased risk would only get a small risk-reduction benefit from use of these drugs.
The task force further found that tamoxifen reduces the risk for nonvertebral fractures and that raloxifene reduces the risk for vertebral fractures in postmenopausal women. However, adequate evidence also showed that the drugs increase the risk for venous thromboembolic events by 4 to 7 events per 1,000 women over 5 years, with tamoxifen increasing the risk more than raloxifene. The potential harm from thromboembolic events was small to moderate, with increased potential for harm in older women.

Adequate evidence showed that tamoxifen, but not raloxifene, raises a woman’s risk for endometrial cancer (four or more cases per 1,000 women). Tamoxifen use may also increase the incidence of cataracts.

Vasomotor symptoms (hot flashes) are a common adverse effect of both tamoxifen and raloxifene, the USPSTF found. Although these symptoms are not typically classified as serious, they can affect the patient’s quality of life and medication adherence.

Overall, the data prompted the USPSTF to conclude with moderate certainty that:

• There is a moderate net benefit from tamoxifen use and raloxifene use to reduce the incidence of invasive breast cancer in women who are at increased risk for the disease.

• The potential harms of tamoxifen and raloxifene outweigh the potential benefits for breast cancer risk reduction in women who are not at increased risk for the disease.