In the weeks surrounding the 2026 annual meeting of the American Society of Clinical Oncology, my phone buzzed with warnings about GLP-1 drugs and cancer. gave The headlines were everywhere. — from NPR and The Washington Post to substacks and heated exchanges on social media — all revolved around the identical claim: Ozempic can reduce cancer risk.
Behind these headlines is one. A real wave of studyWhich includes hundreds of thousands of patients. I’m one. Physician and medical epidemiologistand my team and I design and interpret the identical sorts of studies that test what widely used drugs actually do.
Excitement around the concept that GLP-1 drugs can prevent cancer is running out of evidence. Not mistaken, vital. Not yet earned.
Cancer is one of the vital difficult things to review, since it is just not one disease but greater than 100. Breast cancer, lung cancer and blood cancer usually are not variations of the identical disease. Each has its own unique biology and its own mixture of genetic, environmental and behavioral risks.
No single drug ever gets a definitive answer on the way it affects cancer. It falls asleep, increasing the chance for some, reducing it for others and leaving most untouched.
Early cancer concerns
Before the present buzz that GLP-1 drugs might reduce cancer risk, concern went in the other way: that they could increase cancer risk.
Researchers were originally concerned about thyroid cancer. Studies in mice have found that Ozympic causes thyroid C-cell tumors, which is why U.S. regulators have issued a Black box warning in June 2026 to the drug advising against its use in those with a private or family history of related conditions.
But mice usually are not people. There are human thyroid C cells. Less sensitive to GLP-1 drugs in comparison with rat C cells because they’ve fewer GLP-1 receptors. Long-term studies in monkeys didn’t show the abnormal thyroid cell growth seen in rats.
A 2025 evaluation of knowledge from 93 clinical trials was found No clear link Between taking certain GLP-1 drugs and thyroid cancer. European regulators reached out. Same result 2023 after reviewing the available research on GLP-1s.
Pancreatic cancer was one other concern. Here too, the researchers found An ever-increasing threat In a 2025 evaluation of knowledge from 62 studies taking GLP-1 drugs.
Assurance is real but temporary. These drugs are young, and Cancer can take decades to surface..
The cancer story is turned on its head.
GLP-1 drugs, once investigated for possibly causing cancer, at the moment are being debated as having the potential to stop and even treat cancer.
A 2024 study found greater than 1.6 million individuals with type 2 diabetes. Lower rates of 10 of 13 obesity-related cancers In people treated with a GLP-1 drug in comparison with insulin.
A 2025 study of nearly 87,000 adults found that overall cancer rates amongst those that began a GLP-1 drug About 17 percent lessEndometrial and ovarian cancers were also markedly reduced, in addition to a style of brain cancer called meningioma. Patients taking GLP-1 drugs had a 38% higher risk of kidney cancer, although larger studies are needed to verify this significance.
A study of greater than 110,000 women who underwent breast imaging in 2026 About 30% lower risk of breast cancer in those that use GLP-1 drugs in comparison with those that don’t.
Researchers are also studying how GLP-1 drugs affect a patient’s likelihood of surviving cancer. Among greater than 6,800 colon cancer patients in a 2024 study, 103 of 16 were on a GLP-1 drug. Died within five years in comparison with 37% of those that weren’t taking one. A study presented on the 2026 American Society of Clinical Oncology reported. The risk of death is 34% lower. in six forms of cancer for those taking GLP-1 drugs.
Why is it really easy to misread the evidence?
While these findings are interesting, studies of the results of GLP-1 drugs on cancer risk have three characteristics that make them particularly easy to misread.
The first is Healthy consumer bias. People who start a GLP-1 drug are healthier and wealthier than those that don’t. An obese one who has insurance, sees doctors recurrently and may afford Ozempic is way more prone to start the drug than someone of the identical height and weight who lacks these advantages.
The healthy consumer bias may be very difficult to beat. Observational studywhich compare people as they’re treated in real life somewhat than being randomly assigned to drugs. The very advantages that make it possible to get a GLP-1 prescription, not the drug itself, can reduce a patient’s risk of cancer.
Another comparison is drug selection. To understand the effect of a drug, it needs to be measured against something else. What it’s measured against will shape the consequence of the study. A 2024 study reported that patients taking GLP-1 drugs had a greater reduction in cancer risk than those taking insulin. But a comparison of patients taking GLP-1 drugs with patients taking the diabetes drug metformin showed. No clear reduction in cancer risk.
Insulin is reserved for patients. With more advanced diabetesA condition that itself a Cancer risk factor. In these studies, patients taking insulin started off with the next risk of cancer. Measured against a gaggle at high risk of developing cancer, almost anything can appear protective. The apparent profit got here from the comparator drug, not the GLP-1 drug.
It’s the third time. This is just not one other source of bias as a sign that other biases could also be at work. Cancer can take many years to develop, yet most GLP-1 studies follow people for less than a handful of years. In some studies, GLP-1 drug apparent cancer benefits Show up almost immediately. But prevention doesn’t work that quickly. A drug that really reduced the chance of developing cancer would show its effect regularly as tumor levels decreased over time, not in the primary few months of taking the drug.
While a patient’s risk of cancer begins to diminish almost as soon as they begin treatment, this speed is just not a magical victory for GLP-1 drugs. Rather, in my opinion, it’s telling: People who start these drugs were already at a lower risk of cancer, and the GLP-1 drugs are getting credit for the preexisting profit.
Moreover, just about all of this research comes from a handful of high-income countries, whilst using these drugs is increasing globally and the burden of cancer is increasing. disproportionately grown in low-income countries.. The concept that GLP-1s can reduce the chance of cancer in most parts of the world is being inferred almost entirely from data generated in the rich few.
What do randomized trials show?
The cleanest way around these study biases is randomized trials, which by design make the comparison groups similar from the beginning.
Available clinical trials tell a quieter story than the headlines. Two 2025 meta-analyses, which pooled data from multiple studies; One covers 50 trials. And Second Cover 48 – There is little evidence that GLP-1 drugs increase or decrease the chance of cancer.
Universal Images Group via Michael Silk/UCG/Getty Images
The results of those meta-analyses are generally more reliable than those of observational studies because their total amount of knowledge increases their statistical power. Despite their strengths, these analyzes inherit the restrictions of the trials they included. Most of the trials in these 2025 studies had a brief follow-up of 1 or two years and recorded too few cancer cases to handle the query.
Randomized clinical trials designed to reply the query of whether GLP-1 drugs affect cancer risk would wish to enroll tens of hundreds of individuals and follow them for a few years. Short of that, the following best evidence will come from observational studies designed to simulate randomized trials.
Until then, the concept that GLP-1 drugs reduce cancer risk is a hypothesis that could be tested but has no results to follow.
The bottom line
Based on the available evidence, the clearest conclusion is reassuring: GLP-1 drugs don’t appear to extend overall cancer risk. However, more ambitious claims that GLP-1s actively prevent cancer or improve survival after diagnosis remain unproven.
Assume that GLP-1s impact cancer risk. Researchers still do not know where this effect comes from: Weight loss itselfa broader improvement in, or a more direct effect on, metabolic function Inflammation, immune system or tumors.
The most certain thing I can say can also be the least satisfying: it’s still too early. These drugs are far less common than the cancers they’re credited with stopping.