Weight-Loss Drugs Also Seem to Reduce the Risk of Some Cancers

The most

The drugs that transformed obesity care are now attracting attention in cancer research.

At the American Society of Clinical Oncology’s annual meeting in Chicago, researchers presented three large observational studies on GLP-1 drugs—such as Ozempic, Wegovy, Mounjaro and Zepbound. The studies linked the drugs to lower breast cancer incidence, longer survival in one group of breast cancer patients, and reduced progression to metastatic disease in several common cancers. So how are they doing this?

Lower Rate Signal

In one study, researchers at the University of Pennsylvania examined electronic health records from women who had undergone breast imaging between January 2022 and June 2025.

The team began with more than 217,000 patients, then focused on 94,827 women ages 45 to 80 who had a body mass index above 25.

the threshold for overweight—and a documented imaging result. Doctors had prescribed a GLP-1 drug to 15,107 of those women before their breast exam.

The difference was notable. Researchers diagnosed breast cancer in 1.65% of women who had taken GLP-1 drugs, compared with 2.6% of women who had not. After matching women by age, race, ethnicity, body mass index, breast density and type 2 diabetes status, GLP-1 use remained associated with lower breast cancer incidence.

“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,” Dr. Elizabeth McDonald, a professor of radiology at the University of Pennsylvania, told The Guardian.

“GLP-1 medications are intriguing from a cancer research perspective because they weren’t designed for cancer therapy, but they do affect many different targets and pathways associated with cancer development, so we’re eager to study them in this context.”

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Metastatic Survival Signal

A second study looked at a narrower and more serious setting: hormone receptor-positive, HER2-negative metastatic breast cancer.

Doctors often treat this form of breast cancer with endocrine therapy, which blocks hormones that can fuel tumor growth, and CDK4/6 inhibitors, which slow cancer-cell division. Researchers from IRCCS Istituto Romagnolo per lo Studio dei Tumori “Dino Amadori” in Italy asked whether patients did better when using GLP-1 drugs alongside that standard treatment.

Using the TriNetX Global Collaborative Network, the researchers identified 26,689 patients who received endocrine therapy plus a CDK4/6 inhibitor alone, and 604 patients who also received a GLP-1 drug within three months of starting the cancer drug. After matching the groups, they compared 604 patients in each arm.

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Median overall survival was 67.9 months in the GLP-1 group, compared with 49 months in the group that did not receive a GLP-1 drug. That translated to a 30% lower risk of death.

The study does not show that GLP-1 drugs caused the survival benefit. But it raises a clear question for future trials: could changing weight, insulin signals, inflammation, or estrogen levels make standard breast cancer treatment work better?

Less Progression Signal

The third study, led by Cleveland Clinic researchers, examined whether GLP-1 drugs lowered the risk of cancer spreading after diagnosis.

Researchers used the TriNetX Global Health Research Network to identify patients with stage I to III cancers who started GLP-1 therapy after diagnosis. They compared them with similar patients who took DPP-4 inhibitors, another class of diabetes drugs.

The final matched analysis included seven obesity-related cancers: breast, prostate, non-small cell lung, colorectal, liver, kidney, and pancreatic cancers.

GLP-1 users had lower rates of progression in six of the seven cancers studied. But four reached statistical significance, shown in the table below.

“Our study found that use of GLP-1 drugs, compared to DPP-4 inhibitors and other antidiabetic drugs, was associated with a meaningful reduction in cancer progression across four solid tumor types,” Dr. Mark David Orland of Cleveland Clinic said in a statement. “It provides early evidence that future studies are worth pursuing.”

Signals, Not Proof

The results are encouraging, but they come with a major limit: all three studies were observational. Maybe it’s not the GLP-1 that’s doing something, but rather the patients who receive GLP-1 drugs may differ from other patients in ways that affect cancer outcomes, including weight, diabetes control, access to care, screening, other medications, and overall health.

Researchers tried to account for many of those differences. Still, only randomized clinical trials can show whether GLP-1 drugs directly prevent cancer, slow its spread, or improve survival.

Dr. Marcin Chwistek of Fox Chase Cancer Center, who was not involved in the studies, told The Guardian: “GLP-1 receptor agonists have never been just glucose-lowering drugs. Their anti-inflammatory and immune-modulatory properties have long suggested broader effects.”

For now, the findings are a reason to test GLP-1 drugs in cancer trials, not as evidence that patients should start them to prevent or treat cancer.

The studies appear as 2026 ASCO Annual Meeting abstracts: Abstract 10506 on breast cancer incidence, Abstract 1070 on survival in metastatic breast cancer and Abstract 3143 on cancer progression across seven solid tumors.