Abstract

The risk of incident cancer seems increased in patients with type 2 diabetes (T2D) and therapeutic regimens (metformin; insulin, analogues) may be involved. We investigated in a cohort of 26 742 T2D patients from a statewide disease management program the risk of incident cancer over a median follow-up time of 3.5 years. Data from all T2D patients in the age 40–79 years residing in the Muenster District were linked to cancer cases in the population-based regional cancer registry. Invasive cancer cases were identified using probabilistic record linkage procedures and pseudonymised personal identifiers, including only first cancers but no DCO cases. Censuring date was 31 December 2008. We computed standardised incidence ratios (SIR) and employed Cox regression models. We identified 759 first cancers among male T2D patients (18.7 per 1000 py) and 605 among females (12.7 per 1000 py). Relative to the general population, the risk of any incident cancer was raised (SIR 1.14; 95% CI [1.10 to 1.21]), it was particularly high for cancer of the liver (SIR 1.95 [1.18 to −2.99]) and pancreas (SIR 1.45 [1.07 to 1.92]). In Cox models, adjusting for diabetes duration, body mass index and sex, insulin therapy was related to higher cancer risk (HR 1.69 [1.55 to 1.84]). No effect was seen for metformin. Limitations relate to lack of numbers for analysing specific cancer types and lack of detail on medication type, duration and dosage. Our results seem to confirm previous reports of increased cancer risk with insulin therapy.