P353 Ulcerative Colitis in the IBSEN III study: Frequent use of biologics and low colectomy rates first year of disease

Abstract Background Biological therapy of ulcerative colitis (UC) has become more common in recent years, and colectomy rates have declined during the same period. The aim of this study was to describe the use of first-line biologic therapy and to estimate the colectomy rate in a population-based inception cohort during first year of disease. Methods Inflammatory Bowel Disease in South-Eastern Norway III (IBSEN III) is a population-based inception cohort with a prospective follow-up of newly diagnosed patients with inflammatory bowel disease from the South-Eastern Health Region of Norway, including from 2017 to 2019. In this project, we studied patients≥ 18 years with a verified UC diagnosis at baseline and at one-year follow-up. Baseline characteristics, use of biological therapy, and need for surgery during the first year after diagnosis were analysed. Kaplan-Meier plot was used to estimate the time to first-line biologic therapy. Results A total of 889 UC patients (45.9% female, median age 36 years (range 18-84), 6.2% smokers) were included in the study and met for one-year follow-up. Totally 129 (14.5%) patients started on biological therapy due to UC, during the first year of disease. Time from diagnosis to start of first-line biologic therapy is depicted in Figure 1 (Kaplan-Meier plot). In addition, four patients received biologics due to other indications than UC (not depicted in Figure 1). The colectomy rate at one-year follow-up was 0.9% (8/889). Figure 1: Cumulative incidence of biologic therapy. Conclusion In this population-based inception cohort, colectomy rates during first year of disease were low compared to a prior population-based study from the same geographic area in the pre-biologic era (the IBSEN study)1, while the proportion starting on biological therapy was higher than reported in comparable inception cohorts2. References 1. Moum B, Ekbom A, Vatn MH, et al. Clinical course during the 1st year after diagnosis in ulcerative colitis and Crohn's disease. Results of a large, prospective population-based study in southeastern Norway, 1990-93. Scand J Gastroenterol 1997; 32: 1005-1012. 2. Burisch J, Katsanos KH, Christodoulou DK, et al. Natural Disease Course of Ulcerative Colitis During the First Five Years of Follow-up in a European Population-based Inception Cohort-An Epi-IBD Study. Journal of Crohn's & colitis 2019; 13: 198-208. 2018/10/06. DOI: 10.1093/ecco-jcc/jjy154.