P695 The risk of proximal disease extension in patients with limited ulcerative colitis in a prospective European population-based inception cohort – the ECCO-EpiCom cohort

Background: Ulcerative colitis (UC) is a progressive and dynamic disease and many patients will experience an extension of inflammation from their initial disease location. Disease extent is the most important factor determining disease prognosis over the long-term. As only few population-based studies have investigated the disease extension and subsequent risk of surgery in UC, we sought to investigate this in the European population-based EpiCom-cohort. Methods: The EpiCom-cohort is a population-based cohort of unselected patients with inflammatory bowel disease diagnosed in 2010 in Eastern and Western European centres. Patients were followed prospectively for five years and clinical data were captured throughout the follow-up period and entered in a validated web-based database. Disease extension was defined in patients with limited UC at diagnosis (proctitis, E1 or left-sided, E2) as a progression from the initial extent defined by endoscopy or surgery. The risk of colectomy was assessed in all incident patients. Associations between progression or colectomy and multiple covariates (age, gender, initial disease extent, diagnostic delay, smoking status, increase in extent, geographic region) were analysed by Cox regression analyses using the proportional hazard assumption. Results: A total of 614 incident UC patients were included in the study, of which 390 (64%) had E1 or E2 at diagnosis. Extent at diagnosis and during follow-up is shown in Table 1. During the follow-up period, 68 (18%) patients with E1/E2 progressed to E3, and 20 (5%) patients with E1 progressed to E2. No clinical predictors of extension to either E2 or E3 were identified. During follow-up, a total of 35 (6%) patients had a colectomy. Of patients with E1/E2 as initial extent a total of 18 (5%) patients had a colectomy. Progression from E1/E2 to E3 or from E1 to E2 was a significant risk factor for colectomy (HR 7.4 CI95%: 2.7–20.2). No difference in the results was found between Eastern and Western European patients. Table 1. Disease extent in ulcerative colitis patients at diagnosis and follow-up Conclusions: In this European population-based inception cohort of unselected UC patients one out of four patients with proctitis or left-sided colitis at diagnosis experienced a progression in disease extent after five years of follow-up. The risk of colectomy was increased in patients who progressed to either left-sided or extensive colitis. No clinical predictors for disease extension could be identified, thus highlighting the need for new histological or serological markers in order to identify patients at risk for disease progression.