Women who have taken GLP-1 agonists may gain an additional benefit besides weight loss — significantly lower odds of developing breast cancer, according to research presented June 2 at the American Society of Clinical Oncology (ASCO) meeting in Chicago.
In a retrospective study supported by the American College of Radiology Center for Research and Innovation (ACR CRI) and involving over 110,000 women, researchers led by Elizabeth McDonald, MD, PhD, a professor of radiology at the University of Pennsylvania Perelman School of Medicine, found that women who had received GLP-1 drugs were approximately 30% less likely to have breast cancer compared with those who had not.
“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 McDonald in a statement from the University of Pennsylvania.
In their retrospective study, the researchers reviewed Penn Medicine EHR records for January 2022 and June 2025 and included 111,646 women with a body mass index (BMI) who had breast imaging and a documented outcome. Of this cohort, 15,264 had documented GLP-1 medication prescriptions and 96,382 had no documented GLP-1 prescriptions.
The researchers then created a smaller cohort of 30,528 cases that included one-to-one controls for the 15,264 women who had received GLP-1 drugs. In order to limit bias and potential confounding, these controls were matched across age, race, ethnicity, body mass index (BMI), breast density, and diabetes status.
Lower incidence
The researchers then looked at whether women were diagnosed with breast cancer across both the smaller cohort as well as the full group. The women who received the GLP-1 drugs had 35.1% lower odds of breast cancer compared to the full study group and 30.5% lower odds compared to the controls in the the case-matched cohort.
The authors noted that the study did not account for the type or length of the GLP-1 medication used, genetic risk factors, as well as cancer stage or type at diagnosis. They plan further analyses to address some of these variables.
A large prospective study is now needed to determine whether use of these GLP-1 drugs can help many women avoid developing breast cancer at all, according to ACR Chief Research Officer Etta Pisano, MD. “Given the evidence to date, that is a next logical and potentially lifesaving step,” she said.
“The potential value of this study, and those moving forward to determine causation – is a possible reduction in cancer incidence and costs at the population health level,” Pisano told AuntMinnie. “By identifying tools to help reduce the number of women who develop cancer – and combining those with ever-improving tools, techniques and processes to diagnose and treat cancer – we can greatly reduce the number of breast cancer deaths, the number of women and families impacted by this terrible disease, and possibly reduce the financial costs to the healthcare system and patients.”
What’s next
“We are poised to launch a large-scale clinical trial to test the cancer-preventive impact of GLP-1 agonists within the next few months,” McDonald told AuntMinnie. “We designed the study within the ECOG-ACRIN TMIST population, which includes more than 109,000 women who have been recruited, characterized for breast cancer risk, and undergoing regular screening for breast cancer.”
Many of these women are eligible for participation and have already provided consent to take part in research, she said.
“By leveraging the existing TMIST infrastructure, we can substantially expand the value of participants’ contributions while avoiding the time, cost, and complexity of building a new cohort from the ground up,” she said. “The participants are well characterized, their breast cancer risk profiles are known, and the research infrastructure is already in place, creating a unique opportunity to efficiently evaluate this cancer prevention strategy. We are working hard now to secure funding for the study.”
For more of AuntMinnie’s coverage of ASCO 2026, click here.
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