In the weeks surrounding the 2026 annual meeting of the American Society of Clinical Oncology, my phone buzzed with alerts GLP-1 drugs And cancer. there were headlines everywhere — from NPR and The Washington Post to heated debates on Substack and social media — all making the same claim: Ozempic The risk of cancer may be reduced.
There’s one behind those headlines real wave of studiesWhich includes lakhs of patients. i am one physician and clinical epidemiologistAnd my team and I design and interpret similar studies that test what widely used drugs actually do.
Enthusiasm about the idea that GLP-1 drugs might prevent cancer is running far ahead of the evidence. Not wrong, necessary. No earning yet.
Cancer is one of the most difficult things to study, because it is not a single disease. more than a hundred. Breast cancer, lung cancer and blood cancer are not different forms of the same disease; Each has its own distinct biology and its own mix of genetic, environmental and behavioral risks.
There is never a single drug to make a definitive decision about how it affects cancer. It turns out a hundred, increasing the risk for some, reducing it for others and leaving most untouched.
early cancer concerns
before this current discussion While GLP-1 drugs might reduce cancer risk, concerns were in the opposite direction: that they might increase cancer risk.
Researchers were originally concerned about thyroid cancer. Studies on rodents showed that Ozempic caused thyroid C cell tumors, which is why US regulators added it black box warning in June 2026 for the drug that advises against its use in people with a personal or family history of related conditions.
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But rodents are not people. Human thyroid C cells are less sensitive to GLP-1 drugs compared to rodent C cells because they have far fewer GLP-1 receptors. Long-term studies in monkeys did not show the abnormal thyroid cell growth seen in rodents.
An analysis of data from 93 clinical trials found 2025 no clear link Between taking certain GLP-1 medications and thyroid cancer. European regulators arrived same conclusion in 2023 after reviewing the available research on GLP-1s.
Pancreatic cancer was another concern. Here too, researchers found No persistent increased risk Taking GLP-1 drugs in 2025 in an analysis of data from 62 studies.
The assurance is real but temporary. These drugs are young, and Cancer may take decades to appear.
The story of cancer is at its peak
GLP-1 drugs, once investigated for potentially causing cancer, are now being discussed as drugs that may prevent or even treat cancer.
A 2024 study of more than 1.6 million people with type 2 diabetes found Rates of 10 out of 13 obesity-related cancers reduced In people treated with GLP-1 drugs compared to insulin.
A 2025 study of nearly 87,000 adults found that those who started a GLP-1 drug had lower overall cancer rates. about 17% lessWith a marked reduction in endometrial and ovarian cancer, as well as a type of brain cancer called meningioma. Patients taking the GLP-1 drug had a 38% higher risk of kidney cancer, although larger studies are needed to confirm the significance of this.
A 2026 study of more than 110,000 women undergoing breast imaging found Risk of breast cancer reduced by approximately 30% Those who use GLP-1 medications compared with those who do not.
Researchers are also studying how GLP-1 drugs affect a patient’s chances of surviving cancer. In a 2024 study of more than 6,800 colon cancer patients, about 103% of 16% were on a GLP-1 drug died within five years Compared to 37% who weren’t taking one. A study presented at the 2026 American Society of Clinical Oncology reported 34% less risk of death Six types of cancer for those taking GLP-1 drugs.
Why is it so easy to misread the evidence?
Although these findings are exciting, studies on the effects of GLP-1 drugs on cancer risk have three characteristics that make them particularly easy to misread.
is the first healthy user bias. People who start a GLP-1 drug are healthier and wealthier than those who do not. A person with obesity who has insurance, sees doctors regularly and can afford Ozempic is more likely to start the medication than someone of similar height and weight who lacks those benefits.
Healthy user bias is very hard to get rid of observational studiesWhich compares how people are treated in real life, rather than randomly giving them a drug. The benefits that made it possible to obtain a GLP-1 prescription, not the drug itself, may have reduced patients’ cancer risk.
The second is the choice of a comparative drug. To understand the effect of a drug, it must be measured against something else. What it is measured against will shape the results of the study. A 2024 study reported that patients taking GLP-1 drugs had a greater reduction in cancer risk than patients taking insulin. But when comparing patients taking GLP-1 drug with patients taking diabetes drug metformin, it was found that No apparent reduction in cancer risk.
Insulin is reserved for patients with more advanced diabetesa situation that is itself a risk factors for cancer. In these studies, patients taking insulin had a higher risk of cancer. When measured against a group at higher risk of developing cancer, almost anything can appear protective. The apparent benefit came from the comparison drug, not the GLP-1 drug.
The third is timing. This is not so much a source of bias as a clue that other biases may be at work. Cancer can take decades to develop, yet most GLP-1 studies only follow people for a few years. In some studies, Clear cancer benefits of GLP-1 drugs Show up almost immediately. But prevention does not work that quickly. A drug that actually reduces the risk of developing cancer will show its effect gradually because fewer tumors will appear over time, not just within the first few months of taking the drug.
While a patient’s risk of cancer begins to decline almost as soon as they begin treatment, this pace is not a magical victory for GLP-1 drugs. Rather, in my view, it says: People who started these drugs already had a low risk of cancer, and the GLP-1 drugs are getting credit for that pre-existing benefit.
Furthermore, almost all of this research comes from a handful of high-income countries, even as the use of these drugs is increasing globally and the burden of cancer is increasing. increased disproportionately in low-income countries. The idea that GLP-1s might reduce cancer risk in most parts of the world is being speculated almost entirely from data generated by a wealthy few.
What do randomized trials show?
The clearest way to avoid these study biases is randomized trialWhich by design makes the comparison groups identical from the beginning.
Available clinical trials tell a calmer story than the headlines. Two 2025 meta-analyses, which pooled data from multiple studies – Covers one 50 tests And second to cover 48 – There is little evidence that GLP-1 drugs either increase or reduce cancer risk.
There are several GLP-1 brands available to consumers.
(Image credit: Yulia Burmistrova via Getty Images)
their conclusions Meta-analyses are generally more reliable Compared to observational studies because their total amount of data increases their statistical power. Despite their strengths, these analyzes inherit the limitations of the trials that include them. Most of these 2025 studies had a brief follow-up of one or two years and recorded too few cancer cases to resolve the question.
Randomized clinical trials designed to answer the question of whether GLP-1 drugs affect cancer risk would need to enroll thousands of people and follow them for many years. Furthermore, the next best evidence will come from observational studies designed to simulate randomized trials.
Until then, the idea that GLP-1 drugs reduce cancer risk is a hypothesis worth testing but not a conclusion worth acting on.
bottom line
Based on the available evidence, the clearest conclusion is reassuring: GLP-1 drugs do not appear to increase overall cancer risk. However, more ambitious claims that GLP-1s actively prevent cancer or improve survival after diagnosis remain unproven.
Suppose GLP-1s have an effect on cancer risk. Researchers still may not know where this effect comes from: just lose weightcomprehensive improvement in metabolismor more direct impact on inflammation, immune system Or tumor.
The most certain thing I can say is also the least satisfying: it’s still very early. These drugs are much younger than the cancers they are credited with preventing.
This edited article has been republished Conversation Under Creative Commons license. read the original article.