An observational study published in JAMA Oncology looks at GLP-1 receptor agonists and cancer risk in adults with obesity.
Prof Paul Pharoah, Professor of Cancer Epidemiology, Cedars-Sinai Medical Center, said:
“GLP1 receptor agonists are a fairly new class of agents that can be used to treat type 2 diabetes and help in the management of obesity. Obesity is known to be associated with an increased risk of several different types of cancer, though whether these associations are causal for all cancers is not clear. So it is a reasonable hypothesis that drugs that help reduce weight might also reduce the risk of obesity related cancers. The authors of this study have used a large database of healthcare records of over 20 million individuals in the USA. They identified 44,000 individuals who had been prescribed a GLP1 receptor agonist. These individuals were ‘propensity score matched’ to the same number of individuals who had not been prescribed these drugs. Over an eight year follow-up the incidence of cancer in the individuals who had been prescribed these drugs was 17% lower than the incidence in individuals who had not been prescribed the drugs. This figure is a relative risk reduction – the absolute risk reduction was 2.8 per 1000 person per year. The biggest reduction was observed for ovarian cancer.
“While these results suggest that GLP1 receptor agonist have an effect on cancer risk the presence of an association does not mean that the association is a causal one. While propensity score matching does reduce the chance of bias affecting the results, the study design is still an observational one and there is still the potential for differences between the groups for factors that have not been included in the propensity score. An observational study, no matter how carefully conducted, cannot replicate a randomised controlled trial, which would be regarded as gold standard to evaluate the effects of a drug.
“There is one particular feature of the results that makes me particularly cautious in interpreting them. Figure 2 in the paper shows the cancer risk over time in the two groups. The difference in risk occurs within one year of the start of treatment with GLP1 receptor agonists – after the first year the two lines are completely parallel. This pattern is unlikely if GLP1 receptor agonists had a causal relationship with cancer risk. Such a pattern could easily be explained by increased health surveillance occurring in the months/years before individuals are prescribed these drugs.”
Dr Stephen Lawrence, Associate Clinical Professor, University of Warwick, said:
General Comment:
“The study suggests that using GLP-1 drugs is linked to a lower risk of obesity-related cancers, particularly benefiting certain women’s cancers. However, it did observe a slight increase in kidney cancer cases among GLP-1 users, which was not statistically significant. Further research is needed before drawing any firm conclusions. For most people, the benefits clearly outweigh these relatively minor concerns. The science is promising, but more research will be important to confirm these findings as more individuals begin these treatments.”
What Did the Study Do?
“Trial emulation: instead of a gold-standard randomised trial, clever researchers in Florida, Georgia and Alabama re-created one using real-life health records for over 86,000 adults living with obesity or excess weight.
“Groups compared: about half started on a GLP-1 medicine; the other half did not.”
The Headlines:
“General cancer risk: people taking GLP-1 medications saw slightly fewer cancer diagnoses than those who did not. To put numbers on it: 83 cases per 10,000 patients per year for users, versus 91 per 10,000 for non-users. In practical terms, for every 1,250 people on the medicine, there was one fewer new case of cancer each year.
“Women’s cancers: the study found fewer cases of womb (endometrial), ovarian and certain brain tumours (meningioma) among those taking GLP-1 medicines. Long story short, if you’re using these drugs, your odds dip further when it comes to these specific cancers.
“Other cancers: there were hints of an associated benefit for some other cancer types, like breast and bladder, but not enough to warrant a standing ovation.
“Kidney cancer: this result requires nuance. There was a slight uptick among users—two cases per 1,000 patients per year compared with 1.3 per 1,000 for non-users. That’s about six extra cases for every 10,000 patients treated over a year. Not ideal, but still a drop in the ocean against other health benefits.”
Why Take All This With A Pinch of Salt?
“This was an observational study, despite sophisticated matching and adjustment, it’s not quite as robust as a true randomised trial. Lifestyle factors, severity of obesity, and even how often a GP orders tests could tilt the results.
“Weight loss is a confounder. The drop in cancer might be simply thanks to weight loss itself, not the medicine doing anything fancy. The presence of obesity increases the risk of some cancers.
“There was a short follow-up for cancer. Cancer can brew quietly for years and the study may be too brief to capture very long-term effects.
“Some cancers (like ovarian) had very few cases, making the findings less certain.”
Implications for Patients and the Public:
“For patients: GLP-1 drugs not only help shed pounds and lower blood sugar, but might add a modest bonus by being slightly associated with reducing overall cancer risk, especially for specific women’s cancers. The small associated increase in kidney cancer cases is worth monitoring—not panicking.
“For clinicians: The overall health gains from GLP-1 medications remain far greater than these faint risks. Regular review, patient discussion and ongoing vigilance are key.
“For the wider public: With millions now eligible for GLP-1 therapy, even small shifts in risk matter at scale. Nonetheless, these medicines remain widely safe, with a reassuring cancer profile—and only a whisper of concern about an associated increase in kidney cancer.”
What Needs More Scrutiny?
“1. Longer follow-up: to properly track cancer trends, much longer studies are needed.
“2. Lab work: Is it the drug itself, or just the slimmer waistlines? Laboratory boffins have their work cut out.
“3. **International ** Do results hold beyond the US? British and European populations may differ.
“4. Cancer survivors: Are these drugs safe for those who’ve already had cancer?
“5. Proper randomised trials: this gold standard remains worth pursuing—one for the wish-list.”
‘GLP-1 Receptor Agonists and Cancer Risk in Adults With Obesity’ by Hao Dai et al. was published in JAMA Oncology at 16:00 UK time on Thursday 21 August 2025.
DOI: 10.1001/jamaoncol.2025.2681
Declared interests
Dr Stephen Lawrence: ‘I declare that I have no competing interests. I hold no financial, professional, or personal relationships that could inappropriately influence, or be perceived to influence, the comments I have provided in relation to this review. This declaration is made in the interests of transparency and in keeping with standard academic and professional best practice.’
Prof Paul Pharoah: No conflicts of interest.