Diverging incidences of low-grade dysplasia and advanced neoplasia in inflammatory bowel disease: a nationwide Danish cohort study

BACKGROUND: In individuals with inflammatory bowel disease (IBD), low-grade dysplasia (LGD) is a risk factor for advanced neoplasia, that is, high-grade dysplasia and colorectal cancer. Over recent decades, advances in IBD management and endoscopic surveillance have been implemented; however, it remains unclear whether these developments have influenced the incidence of LGD and advanced neoplasia. OBJECTIVE: To describe contemporary trends in the population-level incidence of LGD and advanced neoplasia in IBD. DESIGN: We conducted a nationwide Danish cohort study (1990-2022) using national healthcare registers. IBD was defined at the second recorded healthcare contact with an IBD diagnosis. Annual age-standardised incidence rates (IRs) per 1,000 IBD patient-years were calculated for LGD and advanced neoplasia. Incidence rate ratios (IRRs) relative to 1990 were estimated using Poisson regression. RESULTS: Among 78,126 individuals with IBD, we identified 6,814 incident cases of LGD and 1,987 of advanced neoplasia. The IR of LGD increased from 0.68 per 1,000 IBD patient-years in 1990 to 4.41 in 2022 (IRR 6.47, 95% confidence interval (CI) 3.99-10.49), with a sustained increase after the introduction of the national general colorectal cancer screening programme in 2014. In contrast, the IR of advanced neoplasia remained stable (IRR 1.10, 95% CI 0.59-2.07). CONCLUSION: The incidence of IBD-related LGD increased markedly over the study period, particularly after the introduction of the national general colorectal cancer screening programme in 2014, whereas the incidence of advanced neoplasia remained stable. These findings highlight the need for robust risk stratification to identify individuals who may benefit from surveillance.