Objectives: Experimental data indicate a possible preventive effect for statins in colorectal cancer (CRC). However, the available epidemiological data are conflicting.
Methods: We conducted a nested case-control study of veterans with diabetes in national databases of the Department of Veterans Affairs (VA) and Medicare-linked files. Cases were defined as incident CRC during January 2001-December 2002, sampled on incidence density. VA pharmacy benefits management (PBM) files were used to identify filled prescriptions for statins. Multivariable conditional logistic regression models were used to estimate odds ratios (ORs) after adjusting for potential confounding variables. Stratified analyses were conducted for potential effect modifiers.
Results: A total of 6,080 cases and 24,320 controls were examined. The mean age was 74 years, and the majority of patients were Caucasian (88%) and male (99%). Filled prescriptions of statins were recorded less frequently in cases (49%) than in controls (52%; OR: 0.88; 95% confidence interval (95% CI): 0.83-0.93). This inverse association remained significant after adjusting for inflammatory bowel disease, diabetes severity, cholecystectomy, liver disease, filled prescriptions for sulfonylurea, aspirin or NSAID use, or colorectal evaluation. Simvastatin comprised the majority (87%) of statin-filled prescriptions, and the association with risk of CRC with simvastatin was very similar to that of any statin. No significant associations were observed between the risk of CRC and nonstatin cholesterol (OR: 1.02; 95% CI 0.88-1.18) or triglyceride-lowering medications (OR: 0.96; 95% CI: 0.87-1.05). The significant inverse association was limited to Caucasians, patients without history of polyps, patients aged 65 years and older, and patients with colon cancer (excluding rectum).
Conclusions: The use of statins was associated with a small reduction in the risk of colon cancer in patients with diabetes. However, the causal link is not clear.