GLP-1 drugs show no overall cancer risk increase but raise thyroid cancer signal in meta-analysis of 50 trials | Research

The takeaway

Meta-analysis of 50 RCTs found GLP-1 drugs do not increase overall cancer risk (OR 1.05, NS), but detected a significant thyroid cancer signal (OR 1.55) and colorectal cancer increase (OR 1.27), while uterine cancer was reduced in obesity trials (OR 0.24).

Thyroid cancer OR 1.55
GLP-1 drugs showed a significant 55% increase in thyroid cancer risk in meta-analysis of 50 trials, more evident with longer use

What the researchers found

Overall cancer: MH-OR 1.05 (NS). Thyroid cancer: OR 1.55 (1.05-2.27, significant, worse in longer trials). Colorectal cancer: OR 1.27 (1.03-1.57, significant in shorter trials only). Uterine cancer in obesity: OR 0.24 (0.06-0.94, significant). No other cancers affected.

Why it matters

With millions taking GLP-1 drugs, cancer safety is critical. This analysis reassures about overall cancer risk but identifies thyroid cancer as a genuine concern requiring ongoing monitoring and uterine cancer reduction as an important benefit.

How the study worked

Meta-analysis of 50 RCTs comparing GLP-1RAs to any comparators for diabetes/obesity, lasting ≥52 weeks. Endpoints: overall and site-specific cancer incidence.

What this study cannot tell us

Cancer as a secondary outcome in most trials (not powered for cancer detection). Short follow-up for cancer development. Thyroid cancer screening practices may vary. Colorectal increase may reflect diagnostic bias.

How to read the evidence

Large meta-analysis of 50 RCTs. Strong for overall cancer reassurance. Thyroid signal is significant but based on small event numbers. Needs prospective cancer-focused studies.

When this study was published

Published in 2025.

The bigger picture

The thyroid cancer signal with GLP-1 drugs has been a long-standing concern since animal studies showed thyroid C-cell hyperplasia. This meta-analysis provides the most robust human evidence yet that the risk may be real, though the absolute increase is small.

Questions still open

Should thyroid screening be recommended for long-term GLP-1 drug users?
Does the uterine cancer reduction persist with longer follow-up?
Is the colorectal cancer signal real or an artifact of increased diagnostic workup?

Common questions

Do GLP-1 drugs cause cancer?

This analysis of 50 clinical trials found no increase in overall cancer risk. However, thyroid cancer risk was 55% higher with GLP-1 drugs, especially with longer use. Colorectal cancer showed a small increase that may be due to more diagnostic testing rather than actual cancer. Importantly, uterine cancer risk was 76% lower in obese patients.

Should I be worried about thyroid cancer on semaglutide?

The absolute risk increase is small, and thyroid cancer is generally very treatable. However, the signal is statistically significant and more pronounced with longer-term use. If you have thyroid cancer risk factors or notice neck lumps, discuss monitoring with your doctor. The overall benefits of GLP-1 drugs (mortality reduction, cardiovascular protection) far outweigh this risk for most patients.

Read the original research

GLP-1 receptor agonists and the risk for cancer: A meta-analysis of randomized controlled trials.

Diabetes, obesity & metabolism, 27(8), 4454-4468

View on PubMed ↗Publisher’s paper ↗

Citation

Silverii, Giovanni Antonio; Marinelli, Christian; Bettarini, Costanza; Del Vescovo, Gloria Giovanna; Monami, Matteo; Mannucci, Edoardo. (2025). GLP-1 receptor agonists and the risk for cancer: A meta-analysis of randomized controlled trials.. Diabetes, obesity & metabolism, 27(8), 4454-4468. https://doi.org/10.1111/dom.16489