Ozempic and cancer risk: what ASCO data show

GLP-1 drugs – At the American Society of Clinical Oncology (ASCO) meeting, researchers described observational evidence suggesting that people taking GLP-1 receptor agonists like Ozempic may face lower risks of being diagnosed with certain cancers, spreading disease, or dyi

CHICAGO—For thousands of oncology specialists flowing through the American Society of Clinical Oncology meeting, the buzz wasn’t only about new chemotherapy schedules or targeted drug combinations. It was about a diabetes medicine that has become a cultural heavyweight: Ozempic.

At ASCO. GLP-1 receptor agonists—drugs originally designed to treat type 2 diabetes and now widely used for weight loss and metabolic conditions such as heart. liver and kidney disease—moved into the center of cancer conversation. Scientists presented findings that people taking GLP-1 drugs were less likely to be diagnosed with several types of cancer. have those cancers spread. or die from them compared with nonusers and those on other diabetes medications.

The evidence remains observational. Researchers can’t claim cause and effect. Still, the patterns they showed reinforced animal research suggesting GLP-1 drugs do more than shed pounds and improve metabolic health. One potential thread ran through multiple presentations: the drugs may dial down inflammation—an engine of cancer development—and might even act directly on tumors.

Obesity has long been identified as a risk factor for at least 13 types of cancer. Excess weight can promote chronic inflammation. raise insulin levels in the blood. and increase estrogen circulating in the body—each a plausible pathway toward cancer development. Whether GLP-1 treatments reduce cancer risk by reversing these pathways through weight loss. or through some other mechanism entirely. is still an open question.

Among the most striking details came from a team led by radiologist Elizabeth McDonald at the Hospital of the University of Pennsylvania. Her group reported that GLP-1 drugs were linked to a 30 percent lower likelihood of a breast cancer diagnosis in more than 111. 000 women who underwent breast imaging.

Other datasets echoed the direction of that signal. A large analysis from the Virginia Commonwealth University (VCU) Massey Comprehensive Cancer Center. published in JAMA Network Open before the conference. followed breast cancer patients for up to 10 years. It found that people who took GLP-1s had a lower risk of death from any cause and a reduced risk of cancer recurrence compared with patients who did not take them.

The conference also heard that colorectal cancer outcomes may track in the same direction. Another investigation co-led by Massey researchers found that GLP-1 drugs were associated with improved survival among people with colorectal cancer.

A study from the Cleveland Clinic tracked people across seven cancer types. and it added a sharper urgency to the discussion: those taking the drugs were significantly less likely to progress to stage four disease in lung. breast. colorectal and liver cancers. In breast cancer, the reported risk reduction was 43 percent, and in lung cancer it was 50 percent.

Taken together. the collection of studies offers what breast medical oncologist Jasmine Sukumar of the University of Texas MD Anderson Cancer Center called an “interesting signal.” She emphasized that the research teams still only have observational data. “The data are still observational, which means the research teams cannot prove cause and effect,” she said.

Scientists are trying to understand what might be driving the results. Bernard Fuemmeler. associate director of population science at the VCU Massey Comprehensive Cancer Center and a co-author of the breast cancer and colorectal cancer studies presented at ASCO. pointed to the simplest explanation: weight loss. Reducing weight also reduces pathways by which obesity fuels cancer, he explained.

Fuemmeler also said the drugs may reduce deaths through their effect on cardiovascular disease. There’s another hormonal logic too. Fat tissue is a source of estrogen, so shrinking fat tissue can reduce the hormones that promote certain types of breast cancer tumors.

But other evidence presented at ASCO suggests the story might extend beyond weight. GLP-1 drugs could also be working on inflammation, a known driver tied to tumor development. Chronic inflammation can create conditions that help cancers take root and spread. Because GLP-1 receptors are found throughout the body—not just in the gut and pancreas—activating them appears to dampen inflammation through multiple pathways. Researchers described mechanisms that could involve acting on immune cells and endothelial cells and other vascular cells. or influencing body-wide inflammatory cascades that affect multiple organs.

There was also discussion of direct tumor effects. In animal studies, tirzepatide—the dual-receptor drug sold as Zepbound—appears to target tumors in breast cancer and endometrial cancer, possibly by reversing the inflammatory effects of obesity and inhibiting tumor growth.

Not every cancer may respond the same way. One signal from the Cleveland Clinic team suggested that tumors rich in GLP-1 receptors might be more affected. Across seven tumor types, people whose tumors had high GLP-1 receptor content were 33 percent less likely to die during follow-up. People with breast cancer tumors showed the greatest improvements in survival.

Mark Orland of the Cleveland Clinic Taussig Cancer Institute. who led that analysis. said high receptor amounts in breast cancer tumors might explain the survival advantage. but it’s not fully understood. He also stressed the clinical reality that cancers won’t behave uniformly. “Each of these cancers has to be looked at fairly individually and very specifically. stage by stage and mutation by mutation. ” Orland said.

Orland and his Cleveland Clinic colleague Jaroslaw Maciejewski. a co-author on the research. also speculated that GLP-1 drugs might work through something more systemic. Early-stage cancers can only progress in the right environment, often shaped by aging-related chronic inflammation. They suggested this could mean the effect wouldn’t be tumor-specific. One possibility they raised is that GLP-1 drugs might narrow the gap between chronological age and biological age—the apparent age of various tissues—meaning they could affect biological aging more broadly.

Even with the growing list of mechanisms researchers are considering, Orland cautioned against getting ahead of the science. He said it would be “a little bit aggressive” to claim GLP-1 drugs will cure cancer or stop it.

Safety concerns also sit on the table. While there isn’t strong evidence suggesting GLP-1 drugs worsen cancer in humans. the Food and Drug Administration has warned against their use among people with a family history of certain thyroid cancers. citing rodent studies. Cancer patients and survivors would also need to monitor loss of muscle mass. a common side effect of the drugs. if GLP-1s were ever used as part of cancer therapy.

For now. clinicians are holding off on prescribing GLP-1 drugs to prevent or treat cancer until more research arrives—especially human clinical trials that some researchers are already designing. Fuemmeler said the key uncertainty is whether the initial observational results will hold up. “We don’t know for sure if these [initial] results will hold up in a randomized clinical trial,” he said. “All of these mechanisms are really ripe for future investigation.”.

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