Obesity is a known risk factor for breast cancer, so could some women reduce their odds of this common cancer by taking weight-loss drugs such as Wegovy and Zepbound? A new study presented at a major cancer conference in Chicago suggests that possibility.
The study of more than 111,000 women found that those who took popular GLP-1 drugs prescribed for obesity or diabetes had a more than 30% lower risk of breast cancer, though the researchers cautioned that the observational study doesn’t prove the popular weight-loss drugs reduce cancer risk.
Still, along with research released in May that found that GLP-1 users were less likely to see some obesity-related cancers spread, Dr. Elizabeth McDonald, a University of Pennsylvania researcher, said her study linking breast-cancer prevention to GLP-1 drugs should “only increase the possibility there’s a real biological signal” that should be studied in a robust clinical trial.
The study was presented at the recent American Society of Clinical Oncology conference at McCormick Place and published this month in the peer-reviewed medical journal JCO Oncology Practice.
Other than skin cancer, breast cancer is the most common cancer among U.S. women, accounting for an estimated 380,000 cases a year. About one in eight women will be diagnosed with breast cancer at some point.
If GLP-1 drugs helped lower risk of breast cancer, “The benefits would be transformative for women’s health,” said McDonald, a professor of radiology at the University of Pennsylvania Perelman School of Medicine.
The study was based on an examination of the health records of more than 111,000 women 45 to 80 years old who were overweight and had breast imaging done at Penn Medicine facilities. The records, spanning the period from 2022 through mid-2025, showed that more than 15,000 of the women had a prescription for GLP-1 medications, and more than 96,000 had no records of GLP-1 prescriptions. The women who were prescribed GLP-1 medications had a 35.1% lower risk of developing breast cancer.
The researchers also analyzed records to match the 15,000-plus GLP-1 users to a control group, matching the groups across age, race, ethnicity, body mass index, breast density and diabetes status and finding that those who had been prescribed GLP-1 drugs at Penn Medicine were 30.5% less likely to be diagnosed with breast cancer.
The study had some limitations. It didn’t, for instance, specify the type of GLP-1 medications or how long the women took the weight-loss or diabetes medications. The study also didn’t account for genetic risk factors or whether the women’s cancers had reached an advanced stage by the time of diagnosis.
Another limitation: Because the study relied on health records of women who visited Penn facilities, it’s possible that some might have gotten GLP-1 medications elsewhere, such as from a telehealth company or a compounding pharmacy. At the time the study was under way, consumers were flocking to telehealth providers and compounders that sold less-expensive knockoff versions of GLP-1 weight-loss drugs. As a result, some women taking GLP-1 drugs might have been included in the control group.
Now, McDonald and other researchers are seeking funding to do a clinical trial to gauge whether GLP-1 drugs can decrease breast cancer among women at high risk. The study, designed to track participants over five years, also would seek to answer whether GLP-1 drugs can lower the risk of tumors returning in women who’ve previously had breast cancer.
Researchers not involved in the study said it adds to the growing body of research on possible benefits of GLP-1 drugs commonly prescribed for weight loss and to treat Type 2 diabetes. Some GLP-1s also have been approved for sleep apnea and to reduce the risk of heart disease as well. And researchers are studying their potential for treating cancer and addiction.
“I think we’re going to see potential usefulness for cancer survivorship and maybe cancer prevention with some of these newer medications coming on the market,” said Bernard Fuemmeler, an associate director for population sciences at Virginia Commonwealth University Massey Comprehensive Cancer Center.
In May, VCU researchers published a study in the journal JAMA Network Open that suggested that breast-cancer patients who used GLP-1s had better outcomes than those who didn’t.
The VCU study of more than 840,000 patients matched similar groups of breast-cancer patients who had obesity or Type 2 diabetes. Those who took GLP-1s had a higher survival rate after 10 years and were less likely to have tumors return compared to non-users.
Past research has shown that breast-cancer patients who lose weight through treatment or surgery have improved heart health and longevity. Researchers said it makes sense that weight loss from GLP-1 use might also deliver better results for breast-cancer patients.
Read more at USA Today.