GLP-1 drugs linked to 35% lower breast cancer risk in large study

A Penn Medicine study presented Tuesday at the ASCO annual meeting found women taking GLP-1 drugs were up to 35% less likely to develop breast cancer.ascopubs
The retrospective analysis of over 110,000 overweight women eligible for mammograms showed a 1.65% cancer rate among GLP-1 users versus 2.6% for nonusers.consultant360
Separate Cleveland Clinic research at the same conference found GLP-1s reduced cancer spread by 38%–50% across four major tumor types, according to Forbes.forbes

GLP-1 Weight Loss Drugs Linked to Lower Breast Cancer Risk in Large Study

Women who took GLP-1 medications such as Ozempic and Wegovy were approximately 30% less likely to develop breast cancer than those who did not, according to a Penn Medicine study presented Tuesday at the 2026 American Society of Clinical Oncology Annual Meeting in Chicago.

Study Findings

The retrospective analysis examined data from more than 110,000 women who were overweight and eligible for mammogram screening. Among women exposed to GLP-1 medications, 1.65% developed breast cancer compared with 2.6% of those without GLP-1 exposure. The study found GLP-1 exposure was associated with a lower incidence of breast cancer with an odds ratio of 0.649.ascopubs

Elizabeth McDonald, MD, PhD, a professor of Radiology at Penn Medicine, presented the findings during an oral abstract session on prevention, risk reduction, and genetics. The research team conducted the observational study because being overweight or obese — particularly after menopause — is a known risk factor for breast cancer, and GLP-1 drugs have an impact on both weight and low-grade inflammation, which researchers have long suspected may play a role in breast cancer development.pennmedicine

Growing Body of Evidence

The Penn Medicine findings arrive amid a broader wave of research linking GLP-1 receptor agonists to reduced cancer risk. A Cleveland Clinic study also presented at the 2026 ASCO meeting found that cancer patients taking GLP-1 medications were 38% to 50% less likely to experience cancer spread compared to those on other diabetes drugs, across non-small cell lung, breast, colorectal, and liver cancers. That study tracked over 12,000 cancer patients.forbes

Earlier research presented at the San Antonio Breast Cancer Symposium found that GLP-1 users had a 46% lower risk of death from any cause over a roughly 5.5-year follow-up period.breastcancer

Caveats and Next Steps

McDonald cautioned that the findings are observational and preliminary, and more work is needed to understand the mechanisms behind the association. The study builds on what researchers at Memorial Sloan Kettering Cancer Center have described as a growing body of research suggesting these drugs “may also be an important tool in reducing cancer related to obesity,” which has been identified in at least 13 forms of cancer.mskcc

Whether GLP-1 medications might eventually warrant investigation as cancer prevention tools remains an open question that will require randomized controlled trials to answer definitively.