PHILADELPHIA — A retrospective analysis of 111,646 women ages 45 to 80 with a BMI of 25 or above who had breast imaging and a documented clinical outcome in the Penn Medicine electronic health record between January 2022 and June 2025 found that those with documented GLP-1 medication prescriptions had 35.1 percent lower odds of developing breast cancer.
In a matched cohort analysis of 30,528 women—including one-to-one controls for each of the 15,264 GLP-1 users matched by age, race, ethnicity, BMI, breast density, and diabetes status—the odds of developing breast cancer were 30.5 percent lower for those with GLP-1 medication prescriptions. Of the total cohort, 15,264 women (13.7 percent) had documented GLP-1 prescriptions, while 96,382 (86.3 percent) had no documented exposure to these medications.
Elizabeth McDonald, MD, PhD, Professor of Radiology at the University of Pennsylvania Perelman School of Medicine, said: "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." She added: "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 also said: "Ultimately, we want to find better options to prevent breast cancer. 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 did not account for the type of GLP-1 medication, duration of use, genetic risk factors, or cancer stage or type at diagnosis. Researchers hypothesize that GLP-1 medications may inhibit breast cancer development through multiple effects, including reducing systemic inflammation, inducing metabolic changes, and influencing epigenetic regulation. Being overweight or obese, particularly after menopause, is a known risk factor for breast cancer. GLP-1 medications were originally developed to treat type 2 diabetes and are now also widely used for weight management.
McDonald and collaborators are actively working to stand up a multisite clinical trial to assess whether GLP-1 medications can lower breast cancer incidence among women at high risk, including those with a history of breast cancer. The research was presented at the 2026 American Society of Clinical Oncology Annual Meeting (Abstract 10506) and published in JCO Oncology Practice. The study received support from the American College of Radiology Center for Research and Innovation, the Pennsylvania Breast Cancer Coalition, and the Abramson Cancer Center.