KU Cancer Center researchers identify breast cancer prevention drug with fewer daunting side effects
March 10, 2020
By Pauline Horton and Anne Christiansen-Bullers
Women with a high risk for breast cancer can be prescribed drugs to help reduce their risk of cancer, but many don't take the drugs because of their problematic side effects.
Researchers at The University of Kansas Cancer Center have identified a drug that may keep the preventive punch but lessen the strong side effects. The result could mean that more women will stay on the preventive therapy and see better results.
The drug is called Duavee, a medication containing estrogen and anti-estrogen bazedoxifene. Duavee is FDA-approved for hot-flash relief and prevention of osteoporosis, but it's rarely used in women with a high risk of breast cancer because it contains estrogen. (And that's because a higher lifetime exposure to estrogen has been linked to increased breast-cancer risk.)
Pilot study shows promise
Carol Fabian, M.D, founder of KU Cancer Center's Breast Cancer Prevention and Survivorship Research Center, and her team conducted a six-month pilot study of Duavee after studies of the drug's components in animal models suggested it may help prevent breast cancer.
The results of the study, published in Cancer Prevention Research, show that women who took Duavee had a reduction in risk biomarkers for breast cancer. These biomarkers - early warnings that's something's not right - can include breast density as seen on a mammogram, for example. On Duavee study participants had decreased mammographic breast density.
Moreover, participants reported an improvement in one key side effect: temperature fluctuations, also known as hot flashes. They listed their median hot flash score at a 15 at the start of the trial but 0 at the end of the trial. Most women had complete relief of their hot flashes by two weeks into the study.
Why women don't take current chemoprevention
Hot flashes can develop or intensify with all of the standard drugs currently used to reduce the risk of developing cancer for women considered at increased risk for breast cancer. Tamoxifen is one well-known example.
Less than 5 percent of women advised to take chemoprevention drugs actually do, however, because the side effects can initiate or aggravate their menopausal symptoms.
Fabian said women most likely to be interested in taking chemoprevention medicines are in their mid-40s to early 60s - the peak time for menopause transition, where 75 percent of women experience hot flashes and night sweats.
For many, menopause symptoms are severe enough to interfere with their quality of life, and women are not likely to take a medicine that might worsen them.
"We wanted to identify an agent which can reduce risk for breast cancer prevention that alleviates - not exacerbates - hot flashes," Fabian said.
"Hormone replacement relieves hot flashes, but when progestins are added to estrogen as must be done to protect the uterus, an increase in breast cancer risk can result. The bazedoxifene component of Duavee reduces the effect of estrogen on the breast and protect the uterus so that a progestin is not necessary."
Plan for continued research
Duavee may be a preventative therapy solution for those with a high risk of breast cancer, if further testing confirms the findings of the pilot study.
"Based on these results, our team believes this warrants a larger, multi-institution placebo-controlled Phase IIB trial," Fabian said. "For women at high risk for breast cancer, this could mean a safer chemoprevention alternative that improves quality of life."
Learn about the research trial directly from Dr. Fabian. Bench to Bedside video courtesy The KU Cancer Center.