GLP-1 and Cancer: What Did the New Studies Presented at ASCO 2026 Really Show?

GLP-1 receptor agonists, medications that have gained enormous prominence in the treatment of type 2 diabetes and, particularly, obesity, are now becoming part of a discussion that goes far beyond weight loss: what role might these medications play in people with cancer?

At ASCO 2026, the world’s leading oncology meeting, new studies reported highly interesting findings. In some analyses, patients with cancer who were taking GLP-1 receptor agonists had lower rates of progression to metastatic disease and better survival outcomes.

These findings are promising, but they must be interpreted with caution. At this point, we cannot say that medications such as semaglutide or tirzepatide prevent metastases or treat cancer.

What we do have are important scientific signals that warrant further investigation.

GLP-1: Much More Than Weight Loss

GLP-1 receptor agonists were initially developed for the treatment of type 2 diabetes. Subsequently, their powerful effects on appetite regulation and body weight transformed these medications into some of the most important therapeutic options currently available for obesity.

However, their metabolic effects extend beyond weight loss.

In addition to reducing body weight and improving glycemic control, GLP-1 receptor agonists may influence several factors, including insulin resistance, hyperinsulinemia, systemic inflammation, energy metabolism, cardiovascular risk, and certain immunometabolic pathways.

Many of these factors are also related to cancer biology.

This has inevitably raised an important question: could the metabolic benefits of GLP-1 receptor agonists also influence the course of certain cancers?

What Did ASCO 2026 Show?

One of the studies that attracted considerable attention at the meeting was Abstract 3143, presented by researchers from the Cleveland Clinic.

The study used data from the international TriNetX network and evaluated patients with stage I to III cancer who initiated treatment with GLP-1 receptor agonists after their cancer diagnosis.

Seven types of cancer were investigated: breast cancer, non–small cell lung cancer, colorectal cancer, hepatocellular carcinoma, prostate cancer, renal cell carcinoma, and pancreatic adenocarcinoma.

Patients taking GLP-1 receptor agonists were compared with similar patients receiving DPP-4 inhibitors, another class of medications used to treat diabetes. The analysis accounted for several clinical characteristics, including body mass index, glycemic factors, smoking, comorbidities, cancer treatments, and concomitant medications.

Lower Risk of Progression to Metastatic Disease

The results attracted considerable attention.

A statistically significant reduction in progression to metastatic disease was observed in four of the seven cancers evaluated.

For non–small cell lung cancer, the hazard ratio was approximately 0.50, corresponding to about a 50% lower relative risk of progression.

For breast cancer, the hazard ratio was 0.57, corresponding to approximately a 43% lower relative risk.

For colorectal cancer, the hazard ratio was 0.69, corresponding to approximately a 31% lower relative risk.

For hepatocellular carcinoma, the hazard ratio was 0.62, corresponding to approximately a 38% lower relative risk.

For prostate, kidney, and pancreatic cancers, fewer events were also observed numerically in some analyses, but the differences did not reach statistical significance.

In breast cancer, for example, progression to metastatic disease occurred in approximately 10.2% of patients receiving GLP-1 receptor agonists compared with 20.1% in the comparator group.

However, these findings do not demonstrate that GLP-1 receptor agonists prevented metastases.

They demonstrate an association between the use of these medications and a lower rate of disease progression.

That distinction is essential.

What About GLP-1 Receptor Expression Within the Tumor?

Another intriguing finding involved the expression of the GLP-1 receptor itself within tumors.

Using information from The Cancer Genome Atlas, researchers observed that higher tumor expression of the GLP-1 receptor was associated with better overall survival across the cancers evaluated.

When the seven cancer types were analyzed together, higher receptor expression was associated with a mortality hazard ratio of approximately 0.67.

In breast cancer, the association was even more pronounced, with a hazard ratio of approximately 0.55.

This finding is particularly interesting because it raises the possibility that the GLP-1 pathway may be related to tumor biology itself.

However, we still do not know whether this association represents a direct biological effect of GLP-1 signaling on the tumor or simply reflects other favorable tumor characteristics.

What Do We Already Know About GLP-1 and Breast Cancer?

This discussion is especially relevant for women with both breast cancer and obesity.

A study published in JAMA Network Open in 2026 evaluated survival and recurrence among patients with breast cancer who used GLP-1 receptor agonists.

The authors found promising associations between GLP-1 receptor agonist use after a breast cancer diagnosis and improved cancer-related outcomes. However, they clearly emphasized that the retrospective design of the study does not allow causality to be established.

The researchers concluded that prospective studies are needed to better define the potential risks and benefits, optimal timing, and patient profiles for GLP-1 receptor agonist treatment after breast cancer.

Therefore, the overall body of evidence is beginning to point in an intriguing direction, but we are still largely in the hypothesis-generating stage.

Why Could Treating Obesity Influence Cancer?

The relationship between obesity and cancer is complex.

Adipose tissue is not simply a site for energy storage. It is metabolically active and participates in the production of hormones, adipokines, and inflammatory mediators.

Several mechanisms associated with obesity may contribute to carcinogenesis and tumor progression.

Chronic inflammation: Obesity is associated with a persistent state of low-grade systemic inflammation.

Insulin resistance and hyperinsulinemia: Elevated insulin levels and activation of pathways such as IGF-1 may promote cellular proliferation in certain biological contexts.

Hormonal changes: These are particularly relevant in hormone-dependent tumors, including some types of breast cancer.

Adipose tissue dysfunction: Changes in adipokines and the metabolic microenvironment may influence pathways involved in tumor development and progression.

By improving body weight, insulin resistance, and several metabolic abnormalities, GLP-1 receptor agonists could theoretically contribute to a biological environment that is less favorable to tumor progression.

Potential direct effects on cancer cells, immune regulation, and the tumor microenvironment are also being investigated.

Does This Mean That GLP-1 Receptor Agonists Treat Cancer?

No.

This is probably the most important point in this entire discussion.

At present, GLP-1 receptor agonists are not anticancer drugs.

They do not replace surgery, chemotherapy, radiation therapy, endocrine therapy, immunotherapy, targeted therapies, or follow-up with an oncologist.

The findings presented at ASCO 2026 are largely based on real-world data and observational studies.

This type of research is extremely valuable, but it can be influenced by differences between the groups being compared, including factors that statistical analyses cannot completely eliminate.

The JAMA study on breast cancer itself highlights important limitations, including its retrospective design, reliance on electronic health records, lack of individual patient data on weight change, and the inability to determine whether the observed associations resulted directly from the medication.

Therefore, prospective randomized clinical trials are needed before these medications can be considered a strategy for directly modifying cancer outcomes.

Can People With Cancer Use Medications Such as Semaglutide or Tirzepatide?

There is no single answer that applies to every patient.

For some people with cancer and obesity, adequately treating obesity may provide important metabolic, cardiovascular, and functional benefits and could potentially influence certain cancer-related outcomes.

On the other hand, there are clinical situations in which weight loss may be undesirable or even harmful.

Particular caution is required in patients with unintentional weight loss, inadequate food intake, sarcopenia, frailty, cachexia, significant nausea or vomiting, or cancer treatments that already compromise nutritional intake.

Nutritional monitoring becomes particularly important because GLP-1 receptor agonists can substantially reduce food intake.

A 2026 review reported increases in several nutritional deficiencies during GLP-1 receptor agonist treatment, including vitamin D and iron deficiencies, as well as muscle loss, reinforcing the importance of nutritional assessment during therapy.

In patients with cancer, preserving muscle mass and adequate nutritional status is a fundamental part of treatment.

Are We Entering a New Field in Oncology?

Possibly.

For many years, the main question was:

“Are GLP-1 receptor agonists safe in relation to cancer?”

Now, a different question is emerging:

“Beyond treating obesity and diabetes, could these medications positively influence cancer outcomes?”

We do not yet have a definitive answer.

However, the findings presented at ASCO 2026 make this one of the most interesting emerging areas at the intersection of obesity, metabolism, and oncology.

The next essential step will be prospective clinical trials specifically designed to determine whether the associations observed in real-world studies represent a true causal effect.

Take-Home Message

The new studies do not demonstrate that medications such as semaglutide or tirzepatide treat cancer.

However, they provide an important and potentially reassuring signal: current evidence does not suggest worse cancer outcomes, while emerging data indicate an association between GLP-1 receptor agonist use and lower metastatic progression in certain cancers.

At ASCO 2026, the most consistent findings were observed in non–small cell lung cancer, breast cancer, colorectal cancer, and hepatocellular carcinoma.

This represents an important shift in how these medications are being discussed.

Obesity treatment should not be viewed merely as an aesthetic intervention or simply as a way to lower the number on the scale.

Obesity is a chronic disease, and its treatment may have implications for many other health conditions. Oncology now appears to be another field in which this relationship deserves careful and rigorous investigation.

Science has not yet provided the final answer.

But ASCO 2026 has left us with an important question for the years ahead:

Could adequately treating obesity also help change the course of certain cancers?

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