Popular GLP-1 Weight-Loss Drugs Linked to 30% Lower Breast Cancer Risk

New research suggests GLP-1 medications may be associated with a lower likelihood of developing breast cancer.

GLP-1 medications have transformed the treatment of obesity and type 2 diabetes, but researchers are increasingly exploring whether their benefits extend far beyond weight loss. Now, a study involving more than 110,000 women suggests these widely used drugs may also be linked to a substantially lower risk of breast cancer.

Presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting and published in JCO Oncology Practice, the research found that women prescribed GLP-1 medications were about 30% less likely to develop breast cancer than women who had not used the drugs.

The study was led by Elizabeth McDonald, MD, PhD, a professor of Radiology at the University of Pennsylvania Perelman School of Medicine and a breast radiologist at Penn’s Abramson Cancer Center.

“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,” McDonald said.

GLP-1 medications mimic glucagon-like peptide-1, a naturally occurring hormone involved in regulating blood sugar and appetite. Although they were originally developed to treat type 2 diabetes, they are now widely prescribed for weight loss and weight management. Several observational studies have suggested that GLP-1 drugs may be linked to lower cancer risk or better outcomes among cancer survivors. However, prospective clinical trials, which provide stronger evidence, have not yet been completed.

McDonald and her colleagues are now preparing a multisite clinical trial to determine whether GLP-1 medications can reduce breast cancer risk in women considered high risk, including breast cancer survivors.

“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.

Examining More Than 110,000 Women

The study analyzed electronic health records from 111,646 women with a body mass index (BMI) of at least 25, which falls within the overweight range. All participants had undergone breast imaging and had documented outcomes in the Penn Medicine health system between January 2022 and June 2025.

Among them, 15,264 women (13.7%) had documented prescriptions for GLP-1 medications, while 96,382 (86.3%) had no recorded exposure to the drugs.

Researchers evaluated new breast cancer diagnoses in two groups. The first included all 111,646 women. The second was a matched analysis involving 30,528 women, pairing each GLP-1 user with a nonuser who had similar characteristics, including age, race, ethnicity, BMI, breast density, and diabetes status. This approach was designed to reduce potential bias and confounding factors.

Lower breast cancer rates were observed in both analyses. Women taking GLP-1 medications had 35.1% lower odds of developing breast cancer in the full study population and 30.5% lower odds in the matched group.

The analysis did not examine differences between specific GLP-1 drugs, duration of treatment, genetic risk factors, or cancer stage and subtype at diagnosis. The research team plans additional studies to investigate some of these factors.

GLP-1 medications are highly effective for weight loss, and maintaining a healthy weight has long been recommended as a way to reduce breast cancer risk. Excess body weight, particularly after menopause, is a known risk factor for the disease.

Why Might GLP-1 Drugs Affect Cancer Risk?

Scientists have also suspected that chronic low-grade inflammation contributes to breast cancer development. GLP-1 medications reduce systemic inflammation through several biological pathways and may also produce metabolic and epigenetic changes that could help slow or prevent tumor growth. Researchers believe these combined effects may contribute to the lower breast cancer rates observed in the study.

Options for reducing breast cancer risk beyond routine screening with mammography or MRI remain limited. Some people with inherited genetic mutations that greatly increase breast cancer risk may choose prophylactic mastectomy. Tamoxifen can significantly reduce breast cancer incidence in high-risk patients, but many eligible individuals do not take it because of its side effects.

By contrast, GLP-1 medications are already used by millions of Americans, making them a potentially attractive candidate for future cancer prevention strategies if the findings are confirmed in clinical trials.

“Ultimately, we want to find better options to prevent breast cancer,” McDonald said. “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.”

Reference: “GLP-1 Agonists Are Associated With a Significant Reduction in Breast Cancer Incidence in Women” by Elizabeth S. McDonald, Laura B. Gillis, Peter Gabriel, Kham Xapakdy, Anthony Young, Abigail Doucette, Mitchell D. Schnall, John B. Buse and Etta D. Pisano, 2 June 2026, JCO Oncology Practice.
DOI: 10.1200/OP-26-00485

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.

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