The finding
Cancer was one of the most-discussed themes at this year's American Society of Clinical Oncology (ASCO) Annual Meeting, where several research teams reported that people taking GLP-1 receptor agonists — the drug class behind Ozempic, Wegovy, Mounjaro, and Zepbound — appear to have lower rates of cancer than people who don't take them. The signal showed up not just in obesity-linked cancers, but across a range of tumor types.
The most prominent of the studies tracked medical and prescription records of more than 10,000 patients with early-stage cancer and found GLP-1 users had reduced risk in six of seven cancers examined. Researchers are clear about what the data is and isn't: it is correlative, drawn from retrospective records, and far from proof that the drugs treat or prevent cancer.
What they found
Of the seven cancers the analysis looked at, four declined at statistically significant levels among GLP-1 users:
- Breast, liver, colorectal, and non-small cell lung cancer risks declined significantly.
- Kidney and prostate cancer risks declined somewhat.
- Pancreatic cancer rates were affected the least.
One figure researchers highlighted: for non-small cell lung cancer, progression to Stage IV disease was 22.3% among patients not taking a GLP-1, versus 10% among those who were.
The protective signal appeared across cancers, not only those with a well-established link to obesity. That pattern is part of why some researchers suspect GLP-1s may act through metabolic or anti-inflammatory pathways — not weight loss alone.
A separate breast-imaging analysis presented at the same meeting found women ages 45 to 80 on GLP-1 drugs were roughly 30% less likely to develop breast cancer. We covered that study in detail here. Its lead author, Penn radiologist Elizabeth McDonald, noted that "the weight loss alone just didn't account for the magnitude of the observed effect" — echoing the cross-cancer pattern in the larger analysis.
What the data cannot say
These are retrospective, observational analyses — they identify associations, not causes. Dr. Julie Gralow, chief medical officer of ASCO, cautioned that the underlying databases did not capture important details like patients' other health conditions, exercise, or eating habits, any of which could influence both who gets prescribed a GLP-1 and who develops cancer.
At the same time, Gralow said, the findings are consistent with a large existing body of knowledge: obesity is an established driver of about a dozen cancers, and healthy lifestyle changes are known to matter in both illness and recovery. "It ties into a body of knowledge about exercise and healthy lifestyles after a cancer diagnosis," she said. In other words, the result fits what's already understood — but fitting expectations is not the same as proving cause.
Why this matters for women
Several of the cancers where the signal was strongest — breast and colorectal in particular — are among the most commonly diagnosed in women. Colorectal cancer in particular has been rising in younger adults, and is often discussed less than breast cancer despite its prevalence. For the many women already taking GLP-1 drugs for weight or metabolic reasons, a possible reduction in risk across multiple cancers would be meaningful if a trial confirms it.
The key word remains if. None of this is a reason to start — or stay on — a GLP-1 for cancer prevention. It is a reason for researchers to run the controlled studies that can actually answer the question.
What's next
More trials are now beginning to test how GLP-1s might influence chronic inflammation and immune function, both of which can contribute to cancer growth. As one example, oncologist Coral Omene at Rutgers Cancer Institute plans to follow 40 breast cancer patients starting tirzepatide, regularly measuring blood samples, tracking cancer markers, and biopsying fat cells every six months to watch how hormones, inflammation, and immune cells respond. Prospective work like this — rather than another database review — is what would move the field from "appears to" toward something firmer.