A new research letter published in JAMA Oncology reports that semaglutide and tirzepatide—two widely used glucagon-like peptide-1 receptor agonists (GLP-1 RAs) for obesity—are increasingly being prescribed to adults with pre-existing cancer, despite limited evidence on their safety and effectiveness in this population.
Researchers analysed data from the Epic Cosmos Dataset, identifying 569,850 adults diagnosed with one of 14 common cancers between January 2021 and May 2025. Eligible patients had obesity (BMI ≥30) plus at least one obesity-related comorbidity; individuals with type 2 diabetes were excluded. Only injectable formulations were assessed.
Overall, 23,557 patients (4.1%) received a prescription for semaglutide or tirzepatide during the study period. Patients who received GLP-1 RAs were younger (mean 58.7 vs 67.1 years), had higher BMI (mean 37.8 vs 33.3), and were more often female (70.6% vs 52.1%) compared with those who did not receive these medications.
Incident prescribing was low but rose over the study period (from 0.01% to 0.9%; P<.001). Prevalent prescription rates followed the same pattern, reaching 5.1% across all cancer types by May 2025.
Use varied considerably by cancer type. The highest prevalent prescription rates were observed in thyroid cancer (10.1%), breast cancer (7.2%), and endometrial cancer (7.1%), all of which have established links with obesity. The lowest rates occurred in pancreatic (1.3%), liver (2.4%), and lung (2.8%) cancers.
The authors noted that while papillary thyroid cancer is obesity-associated, GLP-1 RAs remain contraindicated for medullary thyroid cancer based on findings from preclinical studies.
Interpretation and Limitations
The study was descriptive in nature and did not analyse treatment outcomes, safety, or clinical effectiveness. The authors also cited limitations, including potential misclassification inherent to EHR data, lack of information on treatment phase (such as active therapy vs survivorship), and no adjustment for confounding variables.
Call for Guidance
There is an urgent need for evidence-based recommendations to optimize safety and outcomes
“Given the rapid and heterogeneous adoption of GLP-1 RAs in populations with preexisting cancer but without diabetes—and absence of cancer-specific prescribing guidelines—there is an urgent need for evidence-based recommendations to optimize safety and outcomes,” noted the authors.
With GLP-1 RA prescribing rising among people with cancer—even in the absence of diabetes—the findings highlight the need for cancer-specific evidence to guide safe and appropriate use. The authors call for research that can inform clinical recommendations, support risk–benefit assessments, and help clinicians navigate the integration of GLP-1 RAs into cancer care.
Paper: Kim CDinan MARobinson TJ, et al. Semaglutide and Tirzepatide Prescribing for Obesity in Patients With Preexisting Comorbid Cancers. JAMA Oncol. Published online November 06, 2025. doi:10.1001/jamaoncol.2025.4560 Access online here.
