GLP-1 drugs tied to lower breast cancer incidence in large study

GLP-1 medications for diabetes and weight loss may also provide protection against breast cancer according to an obervational study. (Image Credit Penn Medicine News)

CANCER DIGEST – June 6, 2026 – Women who used GLP-1 medications were about 30 percent less likely to develop breast cancer than similar women who did not use the drugs, according to a new retrospective study led by researchers at University of Pennsylvania.

The results were presented by Dr. Elizabeth McDonald, MD, PhD, a professor of radiology in Penn’s Perelman School of Medicine at the 2026 American Society of Clinical Oncology annual meeting held at McCormick Place in Chicago, May 29-June 2, and were published in JCO Oncology Practice.

Researchers say the findings are promising, but they caution that the study does not prove the medications prevent cancer.

“While our study was observational and does not definitively confirm an association between GLP-1 medications and reduced breast cancer incidence,” McDonald said in a press release, “it does add to the growing body of evidence suggesting that it’s worth investigating these weight-loss drugs as potential cancer prevention tools.”

The analysis drew on health records for 111,646 women ages 45 to 80 with a body mass index of 25 or higher who underwent breast imaging and had documented outcomes in the Penn Medicine electronic health record between January 2022 and June 2025.

Among them, 15,264 had documented GLP-1 prescriptions, while 96,382 had no recorded exposure. In the full cohort, GLP-1 use was associated with 35.1 percent lower odds of breast cancer, and in a matched cohort designed to reduce bias, the reduction was 30.5 percent.

GLP-1 medications mimic a hormone that helps regulate blood sugar and appetite. Originally developed for type 2 diabetes, they are now widely used for weight management. Researchers are increasingly studying them in cancer prevention because obesity, inflammation, and insulin resistance can all play roles in cancer risk, and the drugs may also affect biological pathways linked to tumor development.

Still, the researchers stressed that the study was observational, meaning it can identify an association but cannot show that GLP-1 drugs directly caused the lower cancer incidence.

To answer that question, the Penn team is planning a multisite clinical trial to test whether the medications could help prevent breast cancer in women at high risk, including some with a prior history of the disease.

“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.”

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.

Sources: Written by CoPilot AI based on Penn Today press release and Penn Medicine News edited by the Medical Digest Publications editor