GLP-1 Drugs Beat Insulin on Cancer Risk, but Only in Milder Diabetes

People who started GLP-1 receptor agonists had a lower risk of developing obesity-related cancers than those who started insulin or sulfonylureas, according to a study published in JAMA Network Open. The gap was 1.25 percentage points against insulin and 1.14 percentage points against sulfonylureas over three years of follow-up. Researchers tracked 359,595 adults treated at UT Southwestern Medical Center, pulling from electronic health records covering Jan. 1, 2010, through July 31, 2025.

The advantage didn't hold across the board. Head-to-head against metformin, SGLT2 inhibitors and DPP-4 inhibitors, GLP-1 drugs showed no statistically significant difference in cancer incidence at either three or five years. The research team, led by Jesús Gibran Hernández-Pérez, used a method called target trial emulation to mimic randomized trial conditions with real-world records, and required a 365-day washout period so they were measuring a fresh start on a drug rather than long-term use.

Diabetes severity split the results cleanly. Among patients with less severe disease and no major complications, the lower cancer risk tied to GLP-1s was strongest. In patients with severe diabetes, including macrovascular disease or advanced kidney disease, the difference against insulin and sulfonylureas lost statistical significance — and SGLT2 inhibitors were linked to a lower three-year cancer risk than GLP-1 drugs.

The authors say the pattern likely reflects two things: how doctors pick medications based on a patient's existing complications, and how sick those patients already are. One clear takeaway stands: GLP-1 receptor agonists did not raise obesity-related cancer risk. The team also cautions against reading the results as a green light for prescribing the drugs purely to prevent cancer.