The Risk of Colorectal Cancer in Patients With Type 2 Diabetes: Associations With Treatment Stage and Obesity

OBJECTIVE: To assess the risk of colorectal cancer associated with type 2 diabetes, as compared with a nondiabetic reference population, and to study additional associations between treatment stage and duration of obesity and colorectal cancer risk. RESEARCH DESIGN AND METHODS: We conducted an observational population-based cohort study within the Clinical Practice Research Datalink (1987-2012). All patients (≥18 years) with at least one prescription for an antidiabetic drug (n = 300,039) were matched (1:1) by birth year, sex, and practice to a comparison cohort without diabetes. Cox proportional hazards models were used to derive adjusted hazard ratios (HRs) for colorectal cancer associated with type 2 diabetes. Within the diabetic cohort, associations of colorectal cancer with treatment stages and duration of obesity (BMI ≥30 kg/m(2)) were studied. RESULTS: After a median follow-up of 4.5 years, 2,759 cases of colorectal cancer were observed among the diabetic study population. Type 2 diabetes was associated with a 1.3-fold increased risk of colorectal cancer (HR 1.26 95% CI 1.18-1.33). Among diabetic patients, no association was found with treatment stages. A trend of increased colorectal cancer risk was observed with longer duration of obesity. Risk of colorectal cancer was significantly increased for patients with recorded duration of obesity of 4-8 years (HR 1.19 1.06-1.34) and >8 years (1.28 1.11-1.49). CONCLUSIONS: Type 2 diabetes is associated with a moderately increased risk of colorectal cancer. Among diabetic patients, an increased risk was observed for patients who suffered from obesity for a total duration of 4 years or more.