GLP-1 Use Linked to 30% Reduced Breast Cancer Risk in Large Cohort Study

New retrospective data presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting suggests that glucagon-like peptide-1 (GLP-1) receptor agonists may significantly reduce the incidence of breast cancer.

The study, led by Elizabeth McDonald, MD, PhD, a professor of Radiology at the University of Pennsylvania Perelman School of Medicine, found that women using these medications were approximately 30% less likely to develop the disease than those who did not.

For oncology nurses, who often serve as the primary point of contact for patient education and survivorship care, these findings offer a glimpse into a potential new era of pharmacological prevention.

Study overview and findings

Researchers analyzed health records from 111,646 women between the ages of 45 and 80 who had a body mass index (BMI) of 25 or higher. The analysis compared 15,264 women with documented GLP-1 prescriptions to a control group of 96,382 women. To ensure accuracy, a matched cohort of 30,528 women was also analyzed, controlling for age, race, ethnicity, BMI, breast density, and diabetes status.

The results were consistent across both groups: the full analysis showed 35.1% lower odds of breast cancer, while the matched cohort demonstrated a 30.5% lower incidence. McDonald noted that while the study was observational, it provides compelling evidence for investigating GLP-1s as cancer prevention tools.

Clinical mechanisms

The potential protective effect of GLP-1s likely stems from multiple pathways. Beyond significant weight loss, which is critical since postmenopausal obesity is a known risk factor, these drugs may reduce systemic inflammation. Researchers also hypothesize that metabolic and epigenetic effects may further inhibit tumor growth.

Implications for nursing practice

McDonald emphasized that these findings carry immediate implications for clinical documentation and patient counseling.

"Our findings suggest that it would be helpful to document GLP use as part of a patient's medical record," she stated in an interview conducted at the conference, noting that this data will facilitate future real-world evidence studies.

Oncology nurses should be prepared to discuss these medications with high-risk patients, keeping the following points in mind:

• Adherence to Indications: Currently, patients should only take GLP-1s for FDA-approved indications, such as type 2 diabetes or weight management, as causality for cancer prevention has not yet been established through prospective trials.
• Side Effect Management: Nurses play a vital role in helping patients manage side effects, which should be balanced against the approved benefits of the drug.
• Prevention Alternatives: While effective, current prevention strategies like tamoxifen often have limited uptake due to side effects; GLP-1s may eventually offer a more tolerable alternative for high-risk populations.

The Path Forward

While the results are encouraging, McDonald cautioned that prospective data remains the gold standard. Plans are already underway for a multisite clinical trial to assess whether GLP-1 medications can lower breast cancer incidence among high-risk women, including those with a previous history of the disease.

Reference

1. McDonald E, et al. GLP-1 use linked to lower breast cancer incidence in large cohort study. JCO Oncol Pract. Published online June 2, 2026. (Presented at ASCO 2026; Abstract 10506).