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Pilot Study Identifies Effects of Bazedoxifene and Conjugated Estrogen on Breast Cancer Risk Biomarkers in High Risk Women

October 25, 2019

Researchers at The University of Kansas Cancer Center have identified an agent that improves risk biomarkers for breast cancer while reducing menopausal side effects in women at increased risk for breast cancer.

Chemoprevention drugs like tamoxifen can reduce the risk of developing breast cancer and may be a therapy option for women considered at high risk for breast cancer. However, less than 5 percent of women advised to follow this prevention therapy do, primarily because side effects include initiated or aggravated menopausal symptoms.

According to Carol Fabian, MD, founder of KU Cancer Center’s Breast Cancer Prevention Center and Breast Cancer Survivorship Center, women most likely to be interested in taking chemoprevention medicines are in their mid-40s to early 60s. This is also the peak time of menopause transition in which 75 percent of women experience temperature fluctuations, commonly referred to as hot flashes, and night sweats. For many, menopause symptoms are severe enough to interfere with 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” Dr. 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.”

Prompted by a preclinical study that suggested a medication containing estrogen and anti-estrogen bazedoxifene may help prevent breast cancer, Dr. Fabian and her team conducted a six-month pilot study of the product, called Duavee®, which is FDA-approved for hot flash relief and prevention of osteoporosis but rarely used in high-risk women because it contains estrogen.

The results of the study, published in Cancer Prevention Research, show that women who took Duavee® had a reduction in mammographic breast density and other risk biomarkers for breast cancer including indicators of growth in breast tissue. Moreover, participants reported an improvement in median hot flash score from 15 at baseline to zero at six months.

“Based on these results, our team believes this warrants a larger, multi-institution placebo-controlled Phase IIB trial,” Dr. Fabian said. “For women at high risk for breast cancer, this could mean a safer chemoprevention alternative that improves quality of life.”

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