Medications to lower breast cancer risk
Healthy, high-risk women may benefit from medications to lower their risk for breast cancer. The two types of medications may be used to lower the risk for breast cancer in women; selective estrogen receptor modulators (SERM) and aromatase inhibitors.
Most of the research on these medications have looked at women with increased risk for breast cancer due to a family history of cancer or certain breast changes found on biopsy. There has been very little research on how well these medications work in women with an inherited mutation linked to breast cancer risk.
High-risk women who wish to consider medications to lower their risk for breast cancer should discuss the benefits, risks and limitations with their health care provider.
The two most commonly used SERMs are tamoxifen and raloxifene.
- Tamoxifen blocks the effect of estrogen on breast tissue. Tamoxifen is approved for use in both pre- and post-menopausal women. When taken for five years, it reduces breast cancer risk by up to 40%; this protective effect continues beyond the five-year treatment period. Tamoxifen may also protect bone density and reduce osteoporosis risk in postmenopausal women who cannot take hormone replacement therapy. Side effects of tamoxifen include an increased risk of endometrial cancer and blood clots.
- Raloxifene works in a similar way as tamoxifen. It is used to lower breast cancer risk in postmenopausal women. Raloxifene has a lower risk for endometrial cancer and blood clots and fewer side effects than tamoxifen. The most common side effects are hot flashes, blood clots, nausea and weight gain.
Aromatase inhibitors are medications that block production of estrogen in postmenopausal women. Common aromatase inhibitors include anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin).
Unlike SERMs, aromatase inhibitors do not improve bone density. In fact, they may actually accelerate bone loss in postmenopausal women. However, aromatase inhibitors tend to cause fewer side effects and do not appear to have the risk of blood clots or endometrial cancer seen with tamoxifen.
No studies have looked at aromatase inhibitors for the prevention of breast cancer in women with an inherited mutation linked to breast cancer.
The following studies are looking at medications to lower the risk for breast cancer in high risk women.
- NCT04067726: RANKL Inhibition and Mammographic Breast Density (TRIDENT). The study is looking at whether the drug denosumab (Prolia) may lower the risk for breast cancer in high risk, premenopausal women. The study is open to high risk women with a family history of breast cancer or an inherited mutation in a gene that is not BRCA1 or BRCA2. The trial may be of interest to women with an inherited mutation in ATM, CHEK2, CDH1, PALB2, PTEN or other genes linked to breast cancer.
- NCT01905046: Metformin to Lower Breast Cancer Risk in High Risk Women. The goal of this study is to test whether metformin, a drug commonly used to treat diabetes, is able to get rid of atypia (early cell changes that are thought to be a marker of breast cancer risk) in women at increased risk for breast cancer.