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JAMA Patient Page
September 3, 2019

Medications to Reduce Breast Cancer Risk

JAMA. 2019;322(9):900. doi:10.1001/jama.2019.12858

The US Preventive Services Task Force (USPSTF) has recently published recommendations on taking medications to reduce breast cancer risk.

Risk Factors for Breast Cancer

About 1 in 8 women have breast cancer in their lifetime. There are certain risk factors that increase the chance of having breast cancer. These include

  • Older age

  • Family history of breast cancer (especially at younger ages)

  • Carrying a BRCA genetic mutation

  • History of chest radiation (such as for lymphoma treatment)

  • Abnormal prior biopsy results (such as atypical ductal hyperplasia, atypical lobular hyperplasia, or lobular carcinoma in situ)

For some women who have combinations of these risk factors and are at higher risk of developing breast cancer, taking medications to lower this risk may be beneficial. However, not all high-risk women benefit from these medications. There are risk calculators available that a doctor can use to assess a woman’s personal breast cancer risk and whether or not medications would be beneficial.

What Medications Can Be Used to Lower Breast Cancer Risk?

Medications used to lower breast cancer risk include selective estrogen receptor modulators (SERMs), such as tamoxifen and raloxifene, and aromatase inhibitors, such as anastrozole and exemestane. SERMs block the effects of estrogen in breast tissue, which decreases breast cancer risk. However, they can enhance estrogen effects in other parts of the body. This results in some potentially serious side effects, such as increased risk of cancer of the uterus, as well as blood clots. Aromatase inhibitors prevent other hormones in the body from becoming estrogen. Side effects of aromatase inhibitors include hot flashes, muscle and bone pain, and possible decreased bone density and increased risk of fractures.

What Is the Patient Population Under Consideration for Taking Medications to Reduce Breast Cancer Risk?

This USPSTF recommendation applies to women without symptoms of breast cancer who have not had breast cancer in the past. For women whose doctors confirm they are at increased risk of breast cancer, the USPSTF recommends medications to reduce breast cancer risk. For women who are not at increased risk, the USPSTF recommends against medications to reduce breast cancer risk.

What Are the Potential Benefits and Harms of Taking Medications to Reduce Breast Cancer Risk?

There is convincing evidence that tamoxifen, raloxifene, and aromatase inhibitors provide at least moderate benefit in reducing risk of invasive estrogen receptor–positive breast cancer in higher-risk women. However, given the side effects of these medications as described above, there are also small to moderate potential harms of using them. Therefore, careful risk assessment is crucial for properly weighing the benefits and harms of using these medications.

How Strong Is the Recommendation to Take Medications to Reduce Breast Cancer Risk?

Based on current evidence, the USPSTF concludes with moderate certainty that there is a moderate net benefit of taking tamoxifen, raloxifene, or aromatase inhibitors to reduce risk of invasive breast cancer in women at increased risk. However, for women not at increased risk of breast cancer, the USPSTF concludes with moderate certainty that the potential harms of taking these medications outweigh the potential benefits.

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Article Information

Conflict of Interest Disclosures: None reported.

Source: US Preventive Services Task Force. Medication use to reduce risk of breast cancer: US Preventive Services Task Force recommendation statement [published September 3, 2019]. JAMA. doi:10.1001/jama.2019.11885

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