USPSTF Updates Guidelines on Preventive Medications for Breast Cancer

The U.S. Preventive Services Task Force (USPSTF) issued an updated recommendation regarding the use of medications, such as tamoxifen and aromatase inhibitors, to reduce the risk of breast cancer. The agency now recommends clinicians offer prescriptions of these medications to postmenopausal women at an increased risk of developing breast cancer.

“Prescribing risk-reducing medications for breast cancer is an uncommon practice among primary care clinicians,” wrote the USPSTF authors, led by Douglas K. Owens, MD, MS, of Stanford University in Stanford, California. “Based on limited survey data, 10% to 30% (depending on medication type) of primary care clinicians report ever prescribing risk-reducing medications for primary prevention of breast cancer, and most have only done so a few times.”

The USPSTF task force conducted a review to update a guideline issued in 2013. Their new guideline was published online ahead of print on September 3 in JAMA.

The task force conducted a systematic review of trials and found “convincing evidence” that risk-reducing medications-including tamoxifen, raloxifene, or aromatase inhibitors-can provide “at least a moderate benefit” in reducing the risk for invasive, estrogen receptor-positive breast cancer. Specifically, this finding is relevant for postmenopausal women considered to be at an increased risk for breast cancer.

Tamoxifen and raloxifene can also reduce the risk of some types of skeletal fractures, according to the review; this benefit is independent of the risk of breast cancer.

The potential benefits of taking these medications does not extend to all women. The reduction in risk for women not at increased risk for breast cancer is “no greater than small,” according to the task force authors.

The review did find that these medications are associated with small to moderate harms. Tamoxifen and raloxifene are associated with an increased risk for venous thromboembolic events; tamoxifen increases that risk more than raloxifene. There is also “adequate evidence” that tamoxifen-but not raloxifene-increases the risk for endometrial cancer in women with a uterus. Those harms, though, do not outweigh the potential benefits.

“The USPSTF concludes with moderate certainty that there is a moderate net benefit from taking tamoxifen, raloxifene, or aromatase inhibitors to reduce risk of invasive breast cancer in women at increased risk,” the authors wrote. They recommend that clinicians offer these medications to women at increased risk.

In an editorial published in JAMA Oncology, Mary B. Daly, MD, PhD, and Eric Ross, PhD, both of Fox Chase Cancer Center in Philadelphia, wrote that the new guideline “continues to bring attention to the challenges of implementation of breast cancer chemoprevention.” While it is estimated that more than 10 million women in the U.S. would be eligible for tamoxifen therapy for breast cancer prevention, a 2010 study found that fewer than 1% were actually taking the medication. A later meta-analysis, conducted in 2016, did find a higher rate, at 16.3%.

“In the new era of precision medicine, there is a realization that one size fits all is no longer acceptable for most treatments,” Daly and Ross wrote. “The new USPSTF statement mirrors this trend by making a strong case for the need to consider the unique risk profiles of potential chemoprevention candidates and incorporate this complex information into risk models for individualized decision-making.”