Popular weight-loss drugs may play surprising role in cancer outcomes

As GLP-1 medications continue reshaping the treatment of obesity and diabetes, researchers are also investigating whether the drugs could influence cancer risk and outcomes.

The American Association for Cancer Research's 2026 Cancer Progress Report, released earlier this month, noted that obesity is a major risk factor for many cancers.

As glucagon-like peptide-1 medications – including semaglutides like Ozempic and Wegovy, and tirzepatides like Mounjaro and Zepbound – are known to cause substantial weight loss and improve metabolic health, they have attracted significant interest among cancer researchers.

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While the AACR report cited studies suggesting GLP-1 medications may reduce the risk of certain cancers, it emphasized that the overall evidence is mixed and more research is needed.

"Randomized clinical trials remain the gold standard ... however, such trials have not yet been conducted specifically to assess cancer outcomes associated with GLP-1 RA use," the report stated.

Sai Yendamuri, M.D., a thoracic surgeon at Roswell Park Comprehensive Cancer Center in Buffalo, New York, reiterated that obesity is a leading cause of cancer, second to smoking. Additional risk factors include alcohol and poor nutrition, he noted, "which are all layered into obesity."

"So if obesity is related to cancer – both in terms of causing it and increasing its progression – the logical question is, would a drug that decreases obesity have an impact?" the doctor, who was not associated with the AACR report, said in an interview with Fox News Digital.

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There are "many lines of evidence" that suggest this would be the case, Yendamuri suggested.

"For example, when people studied patients who were having metabolic surgery to decrease obesity, for example, the incidence of cancer decreased in those patients."

Researchers then started looking at patients who were on GLP-1 receptor agonists, such as Ozempic.

"And then they compared the incidence of cancer in those patients to patients who were not taking GLP-1 receptor agonists – and many of those studies found that the risk of cancer was lower and the survival was higher in the patients taking GLP-1s," the doctor said.

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Although the majority of studies showed this effect, Yendamuri noted that some did not identify a relationship – and a couple of studies even showed an increased risk of some specific cancers, such as thyroid cancer.

"The reason you find this disconnect … is because these are retrospective studies," he said. "That is, they look at existing data, and they're trying to derive associations from existing data … but there are many other variables that can impact the result."

Yendamuri and his team of researchers have conducted their own studies of the relationship between obesity and lung cancer.

"We have found in every investigation we've done that obesity does increase the risk of lung cancer," he shared.

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Obesity also depends on how it's defined and measured, Yendamuri noted. While body mass index (BMI) has traditionally been the standard measure, many obesity researchers are moving away from relying on BMI alone and instead using more precise assessments of body fat composition.

Yendamuri shared two key findings from his research.

"If someone's having a resection, a lung cancer surgery, for patients who are on GLP-1 receptor agonists, the recurrence rate seems to be lower."

Additionally, patients with advanced-stage cancers who are in immunotherapy and taking GLP-1s had lower recurrence rates, he noted.

Based on preclinical laboratory studies, Yendamuri said he believes GLP-1 medications have only a limited direct effect on cancer cells.

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"What we think is happening is that it changes the body’s immune response to cancer cells, and thereby improves its ability to fight cancer cells," he told Fox News Digital.

The effect may differ depending on the type of cancer, Yendamuri said, because the immune response is more important in some cancers than others.

"For example, in some cancers like melanoma, we know that the immune response is incredibly important," he said.

Yendamuri acknowledged that at least some of the cancer benefit likely stems from weight loss.

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"Not every patient who takes GLP-1 receptor agonists responds with a substantial weight loss, so in future trials, it would be interesting to see if the benefit for patients depends on the weight loss," he said.

"If those patients who have weight loss with GLP-1 receptor agonists have the same cancer benefit as patients who do not have weight loss, that will answer that question."

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Depending on the outcomes of future trials, the doctor said he is hopeful that GLP-1 drugs could one day be regarded as a preventive mechanism for cancer.

"More and more, we are realizing that apart from the treatment that you get for cancer, lifestyle modifications – exercise, decreasing weight and now GLP-1 receptor agonists – will all have a role in both enhancing the treatment of cancer as well as preventing second cancers," he said.

Yendamuri emphasized the importance of continued funding for the National Cancer Institute, noting that it supports researchers working to advance cancer research and develop new discoveries.