Nothing here says they do. Across six separate matched comparisons, the GLP-1 arm carried a lower hazard than four rival drug classes and no different a hazard from SGLT2 inhibitors. Every absolute difference sits between 0.04 and 0.15 percentage points [1]. One comparison in the paper is printed three times, in two directions, and that is the part worth your attention. It sits inside a design that was otherwise careful, and beside the larger matched-record study on cancer overall.
What was compared with what
Adults with type 2 diabetes who started a GLP-1 drug were matched one-to-one against adults who started insulin, metformin, a DPP-4 inhibitor, an SGLT2 inhibitor, a sulfonylurea or a thiazolidinedione. Matching used 39 baseline variables covering demographics, conditions, procedures and other prescriptions.
The outcome was a pancreatic cancer diagnosis recorded between 365 and 7,300 days after the first prescription. That first year is deliberately discarded, because pancreatic cancer often causes diabetes months before anyone finds the tumor. Without the gap, the drug someone was prescribed for their new diabetes would look like the cause of the cancer that produced it.
Four lower, one level
Against metformin the hazard ratio was 1.39, interval 1.16 to 1.66, in the comparator’s direction — so the metformin group carried the higher hazard. Sulfonylureas gave 1.37, DPP-4 inhibitors 1.31, thiazolidinediones 1.30 with an interval of 1.001 to 1.678. SGLT2 inhibitors gave 1.08, and that interval crosses one.
Read one at a time, each is a separate observational study with its own matched population. We have written about what that does to an answer and will not repeat it here. What is new is the sixth row.
How large are these differences
Small. The absolute risk differences run from 0.04 to 0.15 percentage points, on underlying risks of roughly one in a thousand.
A hazard ratio of 1.39 sounds like a third more cancer. In this data it is about four extra diagnoses per ten thousand people over a period that can run twenty years. Ratios and counts are two different sentences, and a large ratio on a small base is the easiest number on a page to misread.
What matching does not fix
Nobody here was randomized. People put on insulin have usually had diabetes longer and controlled it worse, and 39 covariates do not erase that. The comparison against insulin is the one most likely to be carrying it, which makes the contradiction in that row doubly awkward.
The record network also only knows what was coded. A diagnosis appears when somebody wrote it down, and so do the conditions used to match on — the same limitation behind the other large matched-record study on cancer.
What the wider cancer evidence adds
A separate matched cohort of 86,632 adults looked at cancer overall rather than one organ[2]. Incidence across fourteen cancers ran 13.6 per 1,000 person-years in GLP-1 users against 16.4 in non-users, a hazard ratio of 0.83 (95% CI 0.76 to 0.91). Pancreatic cancer is not reported separately there, so the two studies answer adjacent questions rather than the same one.
Both are record studies and both share the coding problem. Neither is a trial. What they agree on is a direction, and the direction is away from harm.
What to take from it
No signal that GLP-1 drugs cause pancreatic cancer. That is the useful finding, and it is a negative one.
Anything stronger runs into the comparator problem. “Lower risk” is not a property a drug has on its own, and a difference of a fraction of a percentage point is not something a person can feel either way.