Increased cancer incidence risk in type 2 diabetes mellitus: results from a cohort study in Tyrol/Austria

Background: Recent meta-analyses revealed an association between type 2 diabetes mellitus (T2DM) and cancer. The strongest relationship was demonstrated for liver and pancreatic cancer, followed by endometrial cancer. We aimed at assessing the association between T2DM and cancer specifically for Tyrolean patients. Methods: We investigated cancer incidence in Tyrolean subjects with T2DM by linking the data from the Diabetes and the Cancer Registries. 5709 T2DM patients were included and the sex-and age-adjusted standardized incidence ratio (SIR) was calculated, cancer incidence in the Tyrolean population serving as the standard. Endpoints were the time at which cancer was diagnosed, death or end of the observation period (31 December 2010). Results: Site-specific analyses revealed statistically significantly elevated SIRs for cancer of the pancreas (1.78, 95% CI 1.02, 2.89) and corpus (1.79, 95% CI 1.15, 2.66) for women, and cancer of the liver (2.71, 95% CI 1.65, 4.18) and pancreas (1.87, 95% 1.11, 2.96) for men. Sub-analyses performed according to the time of diabetes diagnosis revealed that SIR was highest in the first year after diabetes diagnosis, but SIR was demonstrated to be elevated in women for cancer of the liver (SIR 3.37, 95% CI 1.24, 7.34) and corpus (SIR 1.94, 95% CI 1.09, 3.20) and in men for liver (SIR 2.71, 95% CI 1.40, 4.74) in the period more than five years after diabetes diagnosis. In addition, increased risk at borderline statistical significance was observed in females for liver cancer (SIR 2.40, 95% CI 0.96, 4.94) and cervical cancer (SIR 1.81, 95% CI 0.87, 3.32) and in males for kidney cancer (SIR 1.65, 95% CI 0.99, 2.57). Conclusion: This study revealed a higher risk for cancer at certain sites in Tyrolean patients with T2DM. However, it is important to interpret the results with great caution due to inherent methodological problems. Optimized care programs for patients with T2DM should be integrated into the recommended procedures for cancer screening.