The association between diabetes mellitus and the risk of anal cancer: Results from a large nationwide cohort study in Taiwan

BACKGROUND: Few studies have investigated the association between diabetes mellitus and risk of anal cancer and the results to date have been inconsistent. We analysed the relation between a history of diabetes and diabetic retinopathy and risk of anal cancer in a nationwide cohort in Taiwan. METHODS: Data from a retrospective cohort study of 5.9 million Taiwanese men and women aged 18-90 years were used for the analysis. Multivariable proportional hazards regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between diabetes diagnosis and diabetic retinopathy and risk of anal cancer. RESULTS: During a mean of 7.8 years follow-up, 2315 anal cancer cases occurred. The HRs (95% CIs) of anal cancer among persons with compared to those without a history of diabetes mellitus was 1.04 (0.95-1.13), and for persons with diabetic retinopathy vs. no diabetic retinopathy was 1.52 (1.20-1.92) and proliferative diabetic retinopathy vs. no proliferative diabetic retinopathy was 1.78 (1.27-2.50), respectively. CONCLUSION: This large-scale cohort study provides evidence of no clear association between diabetes mellitus and anal cancer risk overall, however, there was indication of increased risk among persons with diabetic retinopathy and proliferative diabetic retinopathy. Additional large-scale cohort studies with more comprehensive risk factor data are needed to further clarify these findings.