Jasmin Hundal, Chair of Hematology-Oncology Research Fellowship Working Group at Cleveland Clinic, and Daniel Flora, Medical Oncologist and Medical Director of Oncology Research at St. Elizabeth Healthcare, shared a post together on Substack:
“GLP-1 Medications and Cancer: Our Take From ASCO 2026.
A few years ago, GLP-1 medications were mainly discussed for diabetes, later for obesity, and then for heart disease. Now, we’re starting to see them enter the conversation around cancer.
At ASCO 2026, several studies explored how patients taking GLP-1 drugs like semaglutide and tirzepatide influenced cancer outcomes. The studies covered a range of cancers, including breast, colorectal, lung, endometrial, bladder, and hematologic cancers.
We’ve been paying close attention because metabolic health is increasingly intersecting with cancer care. We have a better understanding that improving weight, insulin resistance, inflammation, and cardiovascular health may influence how cancer develops, progresses, recurs, or responds to treatment. As more patients take these medications or ask whether they should, that question is coming up more and more.
Across several studies, GLP-1 use was associated with lower cancer risk, slower progression, improved survival, or fewer treatment complications in some settings. In breast cancer, GLP-1 use was linked with a lower chance of developing breast cancer, particularly hormone receptor–positive breast cancer, and better survival in some groups. [1-3]
One study looked at seven different early-stage cancers and asked whether patients who started GLP-1 medications after diagnosis were less likely to develop stage IV disease. The signal appeared favorable in several cancers, including breast, lung, colorectal, and liver cancer [4]. In breast cancer specifically, progression to metastatic disease occurred in 10.2% of GLP-1 users compared with 20.1% of matched controls.
Those numbers are definitely impressive, but we should still be careful with how we interpret them.
Most of these studies were with researchers reviewing real-world patient records to compare similar groups. This type of research can be useful because it reflects actual patients in real clinics, along with all the complexity of real life. However, matching patients in a database is still not the same as randomizing them in a clinical trial.
Patients on GLP-1 medications may differ from others in ways that are hard to fully capture, like access to care how often they follow up, lifestyle habits, diet, muscle mass, screening routines, and social support. Researchers can adjust for a lot of factors but those adjustments only work for things that are actually measured and recorded.
That’s why these findings should be considered alongside randomized trial data, where the evidence for cancer prevention has been much less clear so far. While randomized trials of GLP-1 medications have shown strong benefits for weight loss, diabetes management, and cardiovascular health, they haven’t yet demonstrated a convincing overall reduction in cancer.
There is also a timing question. Cancer usually develops over many years, so when a study suggests fewer cancer diagnoses over one or two years, we need to ask what is actually being measured. Did the medication prevent cancer from developing? Did it affect early growth? Did it change screening or detection? Or are we seeing residual differences between patients despite statistical adjustment?
That’s why we view these findings as preliminary rather than definitive. Even so, early results can be useful, especially when they help us to ask better questions.
We know GLP-1 medications can improve weight, blood sugar, insulin resistance, inflammation, and cardiovascular health. By improving the overall metabolic environment, they may help create a body that is less favorable for cancer development or progression. There may also be effects beyond weight loss, including effects on inflammation, immune function, or tumor biology itself, although that science is still developing.
For now, GLP-1 medications should be viewed as metabolic medications with possible cancer-related implications, rather than cancer treatments. Screening, surgery, chemotherapy, radiation, endocrine therapy, immunotherapy, and targeted therapy remain the proven foundations of cancer care. Decisions about starting, continuing, or stopping a GLP-1 medication should be made with the care team, especially during active cancer treatment.
There are also safety considerations to keep in mind. GLP1 medications can cause nausea, vomiting, diarrhea, constipation, reduced appetite, dehydration, and weight loss. While many people find these side effects manageable, others, especially those already facing appetite problems, weight loss, or treatment side effects, may have a harder time.
Many patients are working very hard to maintain strength, nutrition, and muscle through treatment. If GLP-1 medications eventually become part of cancer care in some settings, we will need to be intentional about protein intake, resistance training, hydration, nutrition support, and monitoring for unintended muscle loss.
We think the GLP-1 cancer data are promising, make biological sense, and deserve close attention. They’re solid enough to warrant better trials and more in-depth biological research, but also easy to misread, especially with all the recent media buzz around them.
For patients, the practical takeaway is simple. If you are already taking a GLP-1 medication, or wondering whether one might be appropriate for you, this is a good conversation to have with your care team. The answer should be individualized, taking into account your cancer type, treatment plan, weight history, diabetes or metabolic health, appetite, nutrition, muscle mass, side effects, and goals.”
Other articles about GLP-1 Drugs on OncoDaily.