Drugs like Ozempic and Zepbound are the diet drugs of the moment. These GLP-1 RA — glucagon-like peptide-1 receptor agonist — drugs are medications that mimic the hormone that helps regulate blood sugar levels and appetite. They are approved to treat both diabetes and weight loss, but recent research indicates they seem to do more, such as helping reduce cravings for opioids and alcohol.

A few studies have also linked GLP-1 RAs like semaglutide and tirzepitide to a reduced cancer risk as well as better outcomes in survivors, and now a new study has found that GLP-1 RAs may significantly reduce breast cancer risk.

University of Pennsylvania researchers looked at data from over 111,000 women between the ages of 45 and 80 years old who had undergone breast imaging at Penn Medicine between January 2022 and June 2025. All had a BMI of 25 or more and were considered overweight. A GLP-1 drug had been prescribed for over 15,000 of them.

People who were prescribed a GLP-1 drug had a 30.5 percent lower risk of developing breast cancer than those who were not prescribed one.

When the researchers studied data from the entire study population, they found women who were prescribed a GLP-1 drug had a 35 percent lower risk of developing breast cancer than those without a prescription.

The researchers then also analyzed data from a subset of 30,528 participants: the 15,264 women who were prescribed a GLP-1 RA were matched with the same number of women who were not prescribed one. This one-to-one matched study design let the researchers limit bias by controlling for factors such as age, race, ethnicity, BMI, breast density and diabetes status.

They found those in this second, matched study group who were prescribed a GLP-1 in this secondary analysis had a 30.5 percent lower risk of developing breast cancer than those who were not prescribed one.

If GLP-1 drug treatment could help prevent breast cancer, it would be welcome news. “We have been encouraged by the increase in survival rates over the last few decades, and we would love to see the same for prevention,” Elizabeth McDonald, the first author on the study, said in a statement.

Although the GLP-1 drugs were not designed to treat cancer, they affect many different cellular pathways and targets associated with tumor development.

Maintaining a healthy weight can reduce breast cancer risk, particularly after menopause, suggesting that that is one way the weight loss drugs may work to prevent breast cancer, but researchers don't yet fully understand this association between weight and breast cancer risk.

“The impact of these GLP-1 RAs on cancer risk reduction may be greater than what would be expected from weight loss alone,” said McDonald, a professor of radiology at the University of Pennsylvania Perelman School of Medicine. Although the GLP-1 drugs were not designed to treat cancer, they affect many different cellular pathways and targets associated with tumor development.

One pathway is low-grade inflammation which can increase breast cancer risk. GLP-1 RAs reduce systemic inflammation that may have epigenetic effects, or nongenetic effects that modify gene expression, that limit tumor growth. The metabolic effects of the medications may also serve to limit tumor growth.

The study did not account for variables such as the type of GLP-1 RA prescribed or how long they were used, genetic risk factors, or cancer stage or type at the time of diagnosis. The researchers plan more analyses to consider these variables.

This was an observational study and cannot prove that GLP drugs prevent breast cancer, though it does show a notable association, McDonald, a breast radiologist at the University of Pennsylvania Abramson Cancer Center, pointed out. A randomized clinical trial is still needed to see if GLP-1 RAs can reduce breast cancer risk.

The study is published in JCO Oncology Practice.