GLP-1 Drugs Like Ozempic and Wegovy Linked to 30% Lower Breast Cancer Risk, Major Study Finds

A major new study involving more than 110,000 women has found that popular GLP-1 weight-loss and diabetes drugs — including Ozempic, Wegovy, Mounjaro, and Zepbound — are associated with a roughly 30% lower risk of developing breast cancer.

The findings were presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting and simultaneously published in the journal JCO Oncology Practice. Researchers say the results are promising but stress that clinical trials are needed to confirm whether the drugs directly prevent cancer.

What the Study Found

Researchers at the University of Pennsylvania Perelman School of Medicine and Penn's Abramson Cancer Center reviewed electronic health records from 111,646 women aged 45 to 80 with a body mass index (BMI) of 25 or higher. All women had undergone breast imaging within the Penn Medicine health system between January 2022 and June 2025.

Among the study participants, 15,264 (13.7%) had documented prescriptions for GLP-1 medications, while 96,382 (86.3%) had no documented exposure to the drugs. The research team analysed breast cancer diagnoses across the full population and also in a carefully matched cohort of 30,528 women, pairing each GLP-1 user with a non-user who shared similar characteristics including age, race, ethnicity, BMI, breast density, and diabetes status.

The results were consistent across both analyses:

• Full population: Women taking GLP-1 drugs had 35.1% lower odds of developing breast cancer.
• Matched analysis: They had 30.5% lower odds.

Why This Matters

Breast cancer remains one of the most commonly diagnosed cancers worldwide, and effective prevention options are limited. Current strategies include routine screening through mammography or MRI, and for women with high-risk genetic mutations, preventive surgery such as prophylactic mastectomy.

Tamoxifen can substantially reduce breast cancer incidence in high-risk patients, but many eligible women do not take it due to concerns about side effects.

“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 Dr. Elizabeth McDonald, MD, PhD, a professor of Radiology at Penn Medicine and a practicing breast radiologist at the Abramson Cancer Center.

How GLP-1 Drugs Might Reduce Cancer Risk

Scientists have long known 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. Since 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 may also be at play:

• Reduced inflammation: Chronic low-grade inflammation has been linked to breast cancer development, and GLP-1 drugs are known to reduce inflammation through several pathways.
• Metabolic effects: These medications influence metabolism in ways that may suppress cancer development.
• Epigenetic changes: GLP-1 drugs may affect epigenetic processes that help regulate gene activity, potentially inhibiting tumour growth.

What the Experts Say

Dr. McDonald and her colleagues are now working to launch a multisite clinical trial examining whether GLP-1 medications can lower breast cancer incidence in women considered high risk, including those 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.

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.

Limitations of the Study

The researchers noted several important limitations. The study did not distinguish between specific GLP-1 medications such as Ozempic, Wegovy, Mounjaro, or Zepbound. It also did not account for treatment duration, genetic risk factors, cancer stage, or tumour subtype. Additional analyses are planned to examine some of these variables.

Because this was an observational study, it cannot prove cause and effect. Large prospective clinical trials are needed to determine whether the medications directly reduce cancer risk.

What This Means for Patients

For the millions of women already taking GLP-1 medications for weight management or diabetes, these findings add a potentially significant health benefit to the existing advantages of these drugs. However, experts caution that patients should not start taking GLP-1 drugs solely for cancer prevention until clinical trials confirm the effect.

Regular breast cancer screening remains the most important preventive measure for women of all ages. Anyone concerned about their breast cancer risk should speak with their healthcare provider about the full range of prevention options available.

Frequently Asked Questions

What are GLP-1 drugs?

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.

How much did breast cancer risk decrease in the study?

Women taking GLP-1 medications had approximately 30% lower odds of developing breast cancer compared with non-users. In the full study population, the reduction was 35.1%, and in a carefully matched analysis, it was 30.5%.

Is this proof that GLP-1 drugs prevent breast cancer?

No. This was an observational study, which can identify associations but cannot prove cause and effect. Clinical trials are needed to confirm whether GLP-1 medications directly reduce cancer risk.

Should I take Ozempic or Wegovy to reduce my cancer risk?

Experts advise against taking GLP-1 drugs solely for cancer prevention until clinical trials confirm the effect. These medications are prescription-only and should be used under medical supervision for approved indications such as type 2 diabetes and weight management.

What other breast cancer prevention options are available?

Current options include routine mammography screening, maintaining a healthy weight, regular exercise, limiting alcohol consumption, and for high-risk individuals, medications like tamoxifen or preventive surgery.

Were all GLP-1 drugs studied together?

Yes, the study did not distinguish between specific GLP-1 medications. The researchers analysed all GLP-1 drugs as a group and did not account for treatment duration, so further research is needed to understand whether different drugs within the class offer varying levels of protection.