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

Abstract

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/m2) 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.