Retrospective database analysis of cancer risk in patients with type 2 diabetes mellitus in China

Objective: To investigate the association between type 2 diabetes (T2D) and the risk of overall cancer and site-specific cancers in a Chinese population. Research design and methods: Tianjin Urban Employee Basic Medical Insurance database (2003-2014) was used to identify patients with newly onset T2D in 2009, patients with prevalent T2D prior to 2009, and general individuals without T2D, Overall and site-specific cancer incidence rates and incidence rate ratios relative to general population were calculated for both incident and prevalent T2D cohorts. Multivariate Cox proportional hazards models adjusting for baseline characteristics and potential bias were conducted. Subgroup analyses based on gender and age were further conducted. Results: For the year 2009, 21,208 patients with onset T2D (mean age 58.8 years; 48.1% female), 28,248 patients with prevalent T2D (mean age 63.7 years; 50.2% female) and 744,339 general individuals (mean age 43.2 years; 47.7% female) were identified. Controlling for confounders, diabetic patients had an overall 56%-59% higher risk of developing cancer, among which the highest risks by site were liver (adjusted hazard ratio [aHR] = 1.80-2.48), colorectal (aHR = 2.41-2.69) and stomach (aHR = 2.02-2.51) cancers (all p <.05). Patients with prevalent T2D had increased cancer risk in the pan-creas (aHR = 4.52, p <.001). Female diabetic patients had increased risk in the kidneys (aHR = 3.22-3.31, p <.01). Patients aged between 50 and 59 years had the highest relative risk (90% higher), while the relative risk was the lowest among patients >= 70 (45% higher). Conclusion: Type 2 diabetes was associated with increased overall cancer risk led by liver, colorectal and stomach cancers. Patients with longer diabetes duration were associated with higher pancreatic cancer risk and female diabetic patients had a higher risk of kidney cancer.