Introduction
Weight-dependent and weight-independent mechanisms
Why the evidence remains inconclusive
Important safety considerations
Future directions
References
Further reading
Can metabolic treatments change cancer risk? Studies of GLP-1 receptor agonists examine how weight loss, insulin regulation, and tumor biology may intersect.
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Introduction
Since their approval, glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) have improved management of metabolic conditions such as obesity and type 2 diabetes (T2D). Given the well-established association between weight loss and reduced cancer risk, researchers are investigating whether these drugs could also protect against cancer.
Obesity and T2D, both independently and together, are associated with increased risks of several cancers, with the magnitude varying by cancer type. These correlations have been attributed to a wide range of biological mechanisms, such as sustained hyperinsulinemia, or persistently elevated insulin levels, altered synthesis and activity of steroid hormones, as well as chronic, systemic inflammation.2,3
Being overweight or obese is also associated with conditions like gastroesophageal reflux and steatotic liver disease, both of which can increase the risk of cancer in their respective organs. As compared to metabolically healthy individuals, patients with obesity or T2D may also have worse outcomes, such as shorter progression-free and overall survival after cancer treatment.2,3
Large observational cohort studies suggest that GLP-1 RA treatment is associated with lower rates of some obesity-related cancers compared with other glucose-lowering medications, with these associations differing based on the cancer type and comparator. One large study reported lower risks of endometrial, ovarian, colorectal, gallbladder, liver, pancreatic, and esophageal cancers compared with insulin.
Compared with metformin, that study found no significant reductions and reported a higher kidney cancer risk. Evidence for breast cancer prevention remains unconfirmed.2 Overall, a general dose-dependent reduction in cancer risk has not been established.2,3
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Weight-dependent and weight-independent mechanisms
The review describes cancer risk reductions associated with GLP-1 RA use as comparable to reductions reported with lifestyle interventions (16%) and bariatric surgery (32%); however, these percentages do not measure GLP-1 RA benefits relative to those interventions.2 Possible effects beyond weight loss were suggested by one retrospective study where GLP-1 RA users were 40% less likely to be diagnosed with obesity-associated cancer compared with patients who had undergone bariatric surgery, even with greater weight loss in surgical patients. This comparison cannot establish a weight-independent effect because remaining differences between treatment groups may influence cancer diagnoses.2
GLP-1 RAs can improve insulin sensitivity and reduce hyperinsulinemia, potentially limiting the cancer-promoting effects of insulin and insulin-like growth factors. Preclinical studies also suggest effects on inflammation, oxidative stress, and antitumor immune responses. It remains uncertain whether these mechanisms prevent cancer in humans and whether they reflect direct receptor activation or improved systemic metabolism.2
Why the evidence remains inconclusive
Observational associations have not translated into consistent reductions in cancer in randomized trials. To date, most studies examining the effects of GLP-1 RA treatment have been performed among patients with metabolic dysfunction like obesity and T2D. Since most randomized trials were not originally designed to evaluate cancer outcomes, they are often underpowered to conclude whether GLP-1 RA treatment reduces cancer risk or improves cancer-related outcomes.1–3
A meta-analysis of 50 randomized trials by Silverii and colleagues found no significant difference in overall cancer incidence. Obesity trials showed a lower uterine cancer risk, but diabetes trials did not; this subgroup finding was based on few events and requires confirmation.
Higher thyroid and colorectal cancer risks were also reported. Collectively, the cancer evidence is inconclusive, with no convincing evidence of benefit or harm based on sensitivity and credibility assessments.1,3
Differences in baseline metabolic health, including obesity severity, diabetes duration, insulin resistance, and the use of other glucose-lowering therapies, may also affect cancer risk and outcomes. Residual confounding and screening differences complicate observational comparisons, while few cancer events and limited follow-up constrain trial findings.1–3
Lower cancer incidence also does not demonstrate improved treatment response, reduced recurrence, or longer survival after diagnosis. However, these outcomes require separate investigation.2
New study examines GLP-1 drugs and breast cancer risk
Important safety considerations
Current randomized controlled trials and meta-analyses have not shown an overall increase in cancer incidence. Furthermore, rare or late-occurring malignancies remain difficult to assess.
One study reported 55% higher odds of thyroid cancer and 27% higher odds of colorectal cancer. Importantly, these relative estimates describe differences between treatment groups, rather than the percentages of patients who developed cancer.
Thyroid cancer was uncommon, limiting the absolute increase associated with the reported signal. The colorectal signal was confined to shorter trials and may reflect additional diagnostic investigations prompted by gastrointestinal symptoms; this explanation remains unproven.3
The potential association between thyroid cancer and GLP-1 RA use remains unclear. Preclinical data from rodents suggest that GLP-1 RA treatment may stimulate thyroid C-cell proliferation and tumor formation.
Many GLP-1 RA products carry an FDA boxed warning about thyroid C-cell tumors. As a result, these agents are contraindicated in patients with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2. Importantly, these restrictions vary by product, and rodent findings do not establish the same risk in humans.2,3
An analysis of spontaneous reports in the FDA Adverse Event Reporting System identified a thyroid cancer reporting signal with GLP-1 RAs, while metformin showed no such signal. Voluntary reporting and the absence of appropriate control groups prevent this analysis from establishing incidence or causation.
Detection bias may also contribute to observational findings, as more frequent monitoring could increase cancer diagnoses. Other human studies have reported no significant increase, leaving the association unresolved.1,2
Future directions
Future studies are needed to determine whether GLP-1 RAs can directly prevent cancer development or improve survival in patients with established malignancies. Large prospective clinical trials should assess cancer incidence, disease progression, recurrence, and cancer mortality. These clinical trials could clarify whether the observed reductions in cancer risk are primarily attributable to weight loss and improved metabolic health or whether GLP-1 receptor agonists exert independent anticancer effects.1,2
Translational research should distinguish mechanisms that affect cancer initiation from those that influence established tumors, recurrence, and metastasis. Studies of immune regulation, tumor cell proliferation, apoptosis, or programmed cell death, and the tumor microenvironment may help explain preclinical findings, but clinical benefits remain to be demonstrated. As the availability and access to GLP-1 RAs continue to widen, researchers will have more opportunities to monitor cancer incidence and outcomes over longer periods. Long-term studies could define cancer-specific risks and identify which populations, if any, gain cancer-related benefits.1,2
References
- Yang, K., Liu, C., Guo, Q., & Li, Y. (2026). GLP-1 receptor agonists and noncardiometabolic outcomes: An umbrella review of meta-analyses. JAMA Network Open 9(3). DOI: 10.1001/jamanetworkopen.2026.4722. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2847134
- Valencia-Rincón, E., Rai, R., Chandra, V., & Wellberg, E. A. (2025). GLP-1 receptor agonists and cancer: Current clinical evidence and translational opportunities for preclinical research. Journal of Clinical Investigation 135(21). DOI: 10.1172/JCI194743. https://www.jci.org/articles/view/194743
- Silverii, G. A., Marinelli, C., Bettarini, C., et al. (2025). GLP-1 receptor agonists and the risk for cancer: A meta-analysis of randomized controlled trials. Diabetes, Obesity and Metabolism 27(8); 4454-4468. DOI: 10.1111/dom.16489. https://dom-pubs.pericles-prod.literatumonline.com/doi/10.1111/dom.16489
Further Reading
Last Updated: Oct 21, 2026
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