Background and AimsThe long-term risk of high-grade dysplasia [HGD] and colorectal cancer [CRC] following low-grade dysplasia [LGD] in inflammatory bowel disease [IBD] patients is relatively unknown. We aimed to determine the long-term cumulative incidence of advanced neoplasia [HGD and/or CRC], and to identify risk factors for advanced neoplasia in a nationwide IBD cohort with a history of LGD.MethodsThis is a nationwide cohort study using data from the Dutch National Pathology Registry [PALGA] to identify all IBD patients with LGD between 1991 and 2010 in the Netherlands. Follow-up data were collected until January 2016. We determined the cumulative incidence of advanced neoplasia and identified risk factors via multivariable Cox regression analysis.ResultsWe identified 4284 patients with colonic LGD with a median follow-up of 6.4 years after initial LGD diagnosis. The cumulative incidence of subsequent advanced neoplasia was 3.6, 8.5, 14.4 and 21.7%, after 1, 5, 10 and 15 years, respectively. The median time to develop advanced neoplasia after LGD was 3.6 years. Older age [≥ 55 years] at moment of LGD (hazard ratio [HR] 1.73, 95% confidence interval [CI] 1.44–2.06), male sex [HR 1.33, 95% CI 1.10–1.60], and follow-up at an academic [vs non-academic] medical centre [HR 1.37, 95% CI 1.07–1.76] were independent risk factors for advanced neoplasia following LGD.ConclusionsIn a large nationwide cohort with long-term follow-up of IBD patients with LGD, the cumulative incidence of advanced neoplasia was 21.7% after 15 years. Older age at LGD [≥55 years], male sex and follow-up by a tertiary IBD referral centre were independent risk factors for advanced neoplasia development after initial LGD.