A drug already approved to treat menopause symptoms may also lower the risk of invasive breast cancer, according to new research from a phase 2 clinical trial led by Northwestern Medicine.
The study, presented by Dr. Swati Kulkarni at the American Society of Clinical Oncology (ASCO) Annual Meeting on June 1, 2025, offers early but promising results that could provide new hope for women at risk of breast cancer.
The trial focused on a drug called Duavee, a combination of conjugated estrogens and bazedoxifene, which is already approved by the U.S. Food and Drug Administration (FDA) for relieving menopause symptoms such as hot flashes and night sweats. Researchers wondered if this same drug might also help stop the development of breast cancer.
The study included 141 postmenopausal women from across the U.S. who had been diagnosed with ductal carcinoma in situ (DCIS)—a non-invasive type of breast cancer. DCIS is often described as a “stage zero” cancer and is considered an early warning sign, as it can lead to invasive breast cancer if left untreated. Each year, about 60,000 women in the U.S. are diagnosed with DCIS.
Participants were randomly assigned to receive either Duavee or a placebo for approximately four weeks, the time between their diagnosis and their planned breast surgery. Researchers then analyzed tissue samples from the breast to look for changes.
The results were encouraging. The team found that women who took Duavee had significantly less cell growth in their breast tissue compared to those who received the placebo. Reduced cell growth is considered a good sign, as it may indicate a lower risk of the cells turning cancerous.
One of the most exciting parts of this finding is that Duavee was well tolerated by the participants. Unlike other drugs used to reduce breast cancer risk—such as tamoxifen or aromatase inhibitors, which can cause uncomfortable or even serious side effects—Duavee didn’t lead to the same problems.
In fact, it was originally designed to help women feel better during menopause, so it may offer relief from symptoms and reduce cancer risk at the same time.
Dr. Kulkarni, who led the study, emphasized the importance of this potential dual benefit. She explained that many women at higher risk of breast cancer, especially those with previous high-risk conditions like atypical ductal hyperplasia (ADH), atypical lobular hyperplasia (ALH), lobular carcinoma in situ (LCIS), or a prior diagnosis of DCIS, are often discouraged from using traditional hormone therapy because it might increase their cancer risk. This leaves them with very limited options for managing menopause symptoms.
For these women, Duavee could be a safer and more effective alternative. Since it already has FDA approval for treating menopause symptoms, it’s widely available, and doctors are familiar with prescribing it.
However, Dr. Kulkarni cautioned that more research is needed before Duavee can officially be used for breast cancer prevention. A larger, long-term study will be required to confirm its benefits and determine whether it truly prevents invasive cancer over time.
Still, these early results are promising. They suggest that a treatment already helping women through menopause might also play a role in reducing the risk of breast cancer. If future studies support these findings, Duavee could become an important option for women facing both menopause and elevated cancer risk—helping them feel better now and stay healthier in the future.
If you care about breast cancer, please read studies about a major cause of deadly breast cancer, and this daily vitamin is critical to cancer prevention.
For more information about cancer, please see recent studies that new cancer treatment could reawaken the immune system, and results showing vitamin D can cut cancer death risk.
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