Dr McDonald on the Potential Link Between GLP-1 Use and Breast Cancer Risk

A recent large-scale study presented at the 2026 ASCO Annual Meeting presented by Elizabeth McDonald, MD, PhD, looked back at the medical histories of adult women who were eligible for routine mammograms. McDonald, a professor of radiology at the Hospital of the University of Pennsylvania, explains that women using GLP-1 medications (commonly used for diabetes or weight loss) showed a noticeable reduction in breast cancer diagnoses. What makes this finding particularly strong is that the benefit held true regardless of a woman’s age, race, ethnicity, body mass index (BMI), breast density, or diabetes status.

While these results are incredibly promising, it is important to understand the nature of the study. Because this was an observational study, it cannot prove causality.

For patients currently taking or considering these medications, the medical guidance remains clear:

• Stick to Approved Uses: Individuals should only take GLP-1 medications for their current FDA-approved indications, such as managing type 2 diabetes or chronic weight management. They should not be prescribed or taken solely for breast cancer prevention.
• Manage Side Effects Wisely: If a patient is experiencing adverse effects, they should bed weighed against the direct benefits.
• Track History: It is highly recommended to ensure GLP-1 use and duration are accurately documented in medical records.

Because this data is so encouraging, McDonald explains that there is a formal, prospective clinical trial to find out if GLP-1 drugs truly prevent breast cancer. This upcoming trial will piggyback on an ongoing national breast cancer screening study (TMIST), marking the vital next step toward providing true, evidence-based answers for patients.