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Obesity is a known risk factor for breast cancer, but could some women reduce their chances of this common type of cancer by taking weight loss drugs like Wegovy or Zepbound?
A study of more than 111,000 women published June 2 in a peer-reviewed journal found that women who took the popular GLP-1 drug prescribed for obesity and diabetes had a more than 30% lower risk of breast cancer. However, the researchers cautioned that this observational study does not prove that the popular weight loss drug reduces cancer risk.
University of Pennsylvania researcher Elizabeth MacDonald said that studies linking GLP-1 drugs to breast cancer prevention, along with a study published in May that found GLP-1 users were less likely to see metastasis of some obesity-related cancers, “only raises the possibility that there are real biological signals” that should be studied in robust clinical trials.
Other than skin cancer, breast cancer is the most common cancer among women in the United States, accounting for an estimated 380,000 cases annually. Approximately 1 in 8 women will be diagnosed with breast cancer during their lifetime.
McDonald, a professor of radiology at the Perelman School of Medicine at the University of Pennsylvania, said that if GLP-1 drugs help lower the risk of breast cancer, “the benefits will be transformative for women’s health.”
What researchers know about GLP-1 and breast cancer
McDonald presented the findings at a meeting of the American Society of Clinical Oncology, and the study was published June 2 in the medical journal JCO Oncology Practice. The study examined the health records of more than 111,000 overweight women between the ages of 45 and 80 who underwent breast imaging at health care facilities in Pennsylvania.
Health records from 2022 to mid-2025 show that more than 15,000 women had a prescription for a GLP-1 drug, while more than 96,000 had no record of a GLP-1 prescription. Researchers compared the two groups and found that women prescribed GLP-1 drugs had a 35.1% lower risk of developing breast cancer.
The researchers also analyzed the records to match more than 15,000 GLP-1 users with a control group of non-GLP-1 users. Groups were matched across age, race, ethnicity, BMI, breast density, and diabetes status. When researchers compared the two groups, those prescribed GLP-1 drugs were 30.5% less likely to be diagnosed with breast cancer.
The study did not say what type of GLP-1 drug was used or how long the women took weight loss or diabetes drugs. The study also did not take into account genetic risk factors or whether the cancer was at an advanced stage at the time of diagnosis.
And because the study relied on the health records of women who visited the Pennsylvania facility, it does not address whether the patients received GLP-1 drugs elsewhere, such as through telemedicine companies or compounding pharmacies. During the study period, consumers flocked to telemedicine providers and compounders selling cheap knockoffs of GLP-1 weight loss drugs.
If study participants had secured GLP-1 drugs through a telemedicine provider or compounder, “we would never have known they were taking the drug,” MacDonald said. “There would be people in the control group taking GLP-1, so this would make it less effective.”
McDonald and other researchers are seeking funding to start a clinical trial to evaluate whether GLP-1 drugs can reduce breast cancer cases in high-risk women. The study was designed to follow participants over five years and also seeks to answer whether GLP-1 drugs can reduce the risk of tumor recurrence in women who previously had breast cancer.
Researchers at the University of Pennsylvania who were not involved in the study said the study contributes to growing research into GLP-1 drugs, which are commonly prescribed for weight loss and the treatment of type 2 diabetes. Some GLP-1s have been approved to reduce the risk of sleep apnea and heart disease. And researchers are studying its potential in treating addiction and cancer.
“With some of these new (weight loss) drugs coming to market, I think we’re going to see potential utility in cancer survival and perhaps cancer prevention,” said Bernard Fumeler, associate director of population sciences at the Massey Comprehensive Cancer Center at Virginia Commonwealth University (VCU).
In May, VCU researchers published a study in JAMA Network Open suggesting that breast cancer patients treated with GLP-1 had better outcomes than those who did not take the drug.
The VCU study of more than 840,000 patients matched similar groups of breast cancer patients with obesity or type 2 diabetes. Patients who took GLP-1 had better survival rates and were less likely to have their tumors come back after 10 years than those who did not take GLP-1.
Previous studies have shown that breast cancer patients who lost weight through treatment or surgery had improved heart health and longevity. Therefore, it makes sense that weight loss through the use of GLP-1 could lead to better outcomes for breast cancer patients, the researchers said.
“If we can find ways to reduce the risk of cancer in people who have (greater) risk factors, that’s key to what we want to do in cancer prevention,” Fumeler said.
