Across 13 randomized controlled trials with 13,761 participants, tirzepatide showed no increased risk of overall or specific cancers compared to placebo or other diabetes drugs over 26-72 weeks.
No increased cancer risk (RR 0.78)Across 13 RCTs with 13,761 participants, tirzepatide showed cancer risk identical to controls, with no cases of thyroid cancer despite elevated calcitonin at higher doses
What the researchers found
Over 26-72 weeks across 13 RCTs with 13,761 participants, tirzepatide showed identical cancer risk to pooled controls (RR 0.78; 95% CI: 0.53-1.16; P=0.22). Risk was comparable in patients with and without diabetes. Subgroup analyses showed no difference versus placebo, insulin, or GLP-1 receptor agonists. Only the 10 mg dose showed a lower risk of any cancer versus placebo. Despite elevated serum calcitonin with 10 mg and 15 mg doses, no papillary thyroid carcinoma cases were reported in any trial. No specific cancer type showed increased risk with tirzepatide.
Why it matters
GLP-1 and GIP receptor agonists like tirzepatide stimulate pathways that theoretically could promote cell growth, raising questions about cancer safety — particularly thyroid cancer, given that rodent studies with GLP-1 drugs showed thyroid tumors. This comprehensive meta-analysis of all available RCT data provides the strongest evidence to date that tirzepatide does not increase cancer risk over the study periods evaluated, which is reassuring for the millions of patients taking this drug.
How the study worked
Systematic review and meta-analysis of 13 randomized controlled trials from electronic databases. The primary outcome was overall cancer risk; secondary outcomes were specific cancer types. Tirzepatide groups were compared against pooled controls (placebo, insulin, GLP-1 agonists) and against each comparator separately. Dose-stratified subgroup analyses were performed. Study duration ranged from 26 to 72 weeks.
What this study cannot tell us
The maximum follow-up was only 72 weeks, which is too short to detect cancers with long latency periods. Cancer was not the primary endpoint of the included trials, so detection may be incomplete. The total number of cancer events was small, limiting statistical power to detect modest risk increases or differences in rare cancer types. Post-marketing surveillance with longer follow-up is needed to confirm these findings.
How to read the evidence
This is a systematic review and meta-analysis of 13 randomized controlled trials — high-quality evidence for the timeframes studied. However, the relatively short trial durations and the fact that cancer was not a primary endpoint in the source trials limit the strength of long-term safety conclusions.
When this study was published
Published in 2025, this is the most comprehensive meta-analysis of tirzepatide and cancer risk to date, addressing a critical safety question as the drug's use continues to expand rapidly.
The bigger picture
As incretin-based peptide drugs become among the most prescribed medications worldwide, long-term safety data is critical. This meta-analysis addresses one of the most serious safety concerns — carcinogenicity — and provides evidence-based reassurance. However, the relatively short trial durations mean that cancer risks requiring years of exposure to manifest cannot be ruled out. The elevated calcitonin levels observed with higher doses warrant continued monitoring in post-marketing surveillance studies.
Questions still open
- Will longer-term observational studies (5+ years) confirm the cancer safety seen in these shorter trials?
- Does the elevated calcitonin seen with higher tirzepatide doses have any clinical significance over longer exposure periods?
- Is the non-significant trend toward lower cancer risk with tirzepatide (RR 0.78) a real protective effect or statistical noise?
Common questions
Does tirzepatide (Mounjaro/Zepbound) cause cancer?
Why were there concerns about thyroid cancer with GLP-1 drugs?
Read the original research
Tirzepatide and Cancer Risk in Individuals with and without Diabetes: A Systematic Review and Meta-Analysis.
Endocrinology and metabolism (Seoul, Korea), 40(1), 112-124
Citation
Kamrul-Hasan, A B M; Alam, Muhammad Shah; Dutta, Deep; Sasikanth, Thanikai; Aalpona, Fatema Tuz Zahura; Nagendra, Lakshmi. (2025). Tirzepatide and Cancer Risk in Individuals with and without Diabetes: A Systematic Review and Meta-Analysis.. Endocrinology and metabolism (Seoul, Korea), 40(1), 112-124. https://doi.org/10.3803/EnM.2024.2164