Long‐term incidence of dysplasia and colorectal cancer in an ulcerative colitis population‐based cohort

Abstract Background Ulcerative colitis (UC) is a risk factor in developing colorectal cancer (CRC). Surveillance programmes aim to identify premalignant lesions to facilitate improved treatment outcomes. Recent studies have suggested that the risk of CRC in UC has decreased. This study aims to characterize the risk of CRC in UC in a population‐based New Zealand cohort. Methods All patients in the Canterbury Inflammatory Bowel Disease Study, a comprehensive population‐based cohort, were reviewed and cases of dysplasia and CRC identified. Demographic data and risk factors were assessed and standardized incidence ratios (SIRs) calculated comparing with the national population. Results A total of 518 UC cases were analysed (46.3% female). Median follow‐up was 17.5 years (interquartile range 12.2–25.1 years). Neoplasia developed in 42 (8.1%) patients, 14 (2.7%) of whom had CRC. The mean age at CRC diagnosis was 63.3 years, and mean duration with UC before CRC 18.4 years (0–36.8 years). The total incidence rate was 1.35/1000 person‐year duration (95% confidence interval 0.74–2.27). The age‐adjusted SIR was 1.74 (95% confidence interval 1.03–2.93) compared to the New Zealand population. Risk factors for any dysplasia included disease extent and male gender. Conclusion In this population‐based cohort with long‐term follow‐up, the SIR of CRC in UC patients was significantly lower than the initial epidemiological studies although similar to more recent studies. This increased risk still justifies ongoing screening in the UC population.