Popular medications such as Ozempic, Wegovy, Mounjaro, and Zepbound may offer an unexpected benefit beyond helping people lose weight and manage diabetes. New research involving more than 110,000 women found that those taking GLP-1 drugs, a category that includes semaglutide-based medications like Ozempic and Wegovy, were significantly less likely to develop breast cancer.
The findings were presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting and published in JCO Oncology Practice. Researchers reported that women using GLP-1 medications had roughly a 30% lower likelihood of developing breast cancer compared with women who were not taking the drugs.
“While our study was observational and does not definitively confirm an association between GLP-1 medications and reduced breast cancer incidence, it does add to the growing body of evidence suggesting that it’s worth investigating these weight-loss drugs as potential cancer prevention tools,” said Elizabeth McDonald, MD, PhD, a professor of Radiology at the University of Pennsylvania Perelman School of Medicine and a practicing breast radiologist at Penn’s Abramson Cancer Center.
Ozempic, Wegovy, and Other GLP-1 Drugs Draw Cancer Research Interest
GLP-1 medications mimic a naturally occurring hormone called glucagon-like peptide-1, which helps regulate appetite and blood sugar levels. The class includes semaglutide drugs such as Ozempic and Wegovy, as well as tirzepatide medications including Mounjaro and Zepbound. Although originally developed to treat type 2 diabetes, these drugs have become some of the most widely used weight-loss medications in the United States.
In recent years, several observational studies have suggested that GLP-1 drugs may be associated with lower risks for certain cancers or improved outcomes among cancer survivors. However, researchers stress that observational studies alone cannot prove cause and effect. Large prospective clinical trials are still needed to determine whether the medications directly reduce cancer risk.
To answer that question, McDonald and her colleagues are working to launch a multisite clinical trial examining whether GLP-1 medications can lower breast cancer incidence in women considered high risk, including some with a previous history of breast cancer.
“GLP-1 medications are intriguing from a cancer research perspective because they weren’t designed for cancer therapy, but they do affect many different targets and pathways associated with cancer development, so we’re eager to study them in this context,” McDonald said.
Study of More Than 110,000 Women Finds Lower Breast Cancer Rates
The research team reviewed electronic health records from 111,646 women between the ages of 45 and 80 who had a body mass index (BMI) of 25 or higher and underwent breast imaging within the Penn Medicine health system between January 2022 and June 2025.
Among those women, 15,264 (13.7 percent) had documented prescriptions for GLP-1 medications, while 96,382 (86.3 percent) had no documented exposure to the drugs.
Researchers evaluated new breast cancer diagnoses in two separate groups. The first included the entire population of 111,646 women. The second was a matched cohort of 30,528 women, pairing each GLP-1 user with a nonuser who shared similar characteristics, including age, race, ethnicity, BMI, breast density, and diabetes status. This approach was designed to reduce bias and account for potential confounding factors.
The results were consistent in both analyses. In the full study population, women taking GLP-1 medications had 35.1 percent lower odds of developing breast cancer. In the matched analysis, they had 30.5 percent lower odds.
The researchers noted several limitations. The study did not distinguish between specific medications such as Ozempic, Wegovy, Mounjaro, or Zepbound. It also did not account for treatment duration, genetic risk factors, cancer stage, or tumor subtype. Additional analyses are planned to examine some of these variables.
Why Weight-Loss Drugs Might Influence Breast Cancer Risk
Scientists have long recognized that maintaining a healthy weight is an important part of breast cancer prevention. Excess weight, particularly after menopause, is a well-established risk factor for the disease.
Because GLP-1 medications are highly effective at promoting weight loss, some of the observed benefit may be related to weight reduction. However, researchers suspect other biological mechanisms could also be involved.
Chronic low-grade inflammation has long been considered a possible contributor to breast cancer development. GLP-1 drugs are known to reduce inflammation through several pathways. They also influence metabolism and can affect epigenetic processes that help regulate gene activity. Researchers currently believe these combined effects may help suppress the development of breast cancer.
Could Ozempic and Similar Drugs Help Prevent Breast Cancer?
Current options for reducing breast cancer risk remain relatively limited.
Along with routine screening through mammography or MRI, some individuals with inherited genetic mutations that greatly increase breast cancer risk may choose preventive surgery, including prophylactic mastectomy.
Tamoxifen can substantially reduce breast cancer incidence in high-risk patients, but many eligible women do not take the drug because of concerns about side effects.
By contrast, GLP-1 medications such as Ozempic, Wegovy, Mounjaro, and Zepbound are already being used by millions of Americans, making them an especially appealing area for future prevention research.
“Ultimately, we want to find better options to prevent breast cancer,” McDonald said. “It’s been encouraging to see the survival rates for breast cancer improve over recent decades, and we’d love to see the same gains in prevention.”
The study was supported by the American College of Radiology Center for Research and Innovation, the Pennsylvania Breast Cancer Coalition, and the Abramson Cancer Center.