P078 Pediatric onset IBD has a more severe disease course compared to adulthood onset: A population-based study
Authors: Mikkel Malham , Christian Jakobsen , Ida Vind , Marianne Vester-Andersen , Vibeke Wewer 
Published: July 2019

BACKGROUND:
The existing population-based comparative studies between adult onset IBD (aIBD) and pediatric onset IBD (pIBD) consistently report, that pediatric onset of ulcerative colitis (pUC) present with more extensive disease. In this population-based study, we aim to further characterize the differences in the natural history between pIBD and aIBD.

METHODS:
AIBD patients included (>18 years of age) were diagnosed from January 2003 to December 2004. PIBD patients were diagnosed from January 1998 to December 2008 (<15 years of age). Both cohorts are population-based. All medical records were retrieved manually at time of last follow-up, and clinical data concerning IBD phenotype (Montreal classification1) and treatment were registered. Number of relapses were recorded as defined by Romberg-Camps et al2. Differences regarding medical treatment and surgery was calculated using Cox regression analysis. Comparison of risk of relapse (IRR) was calculated using Poisson regression. All other comparisons were calculated using Chi2.

RESULTS:
446 aIBD (CD/UC 183/263) and 333 pIBD (CD/UC/IBDU 166/145/22) patients were included. Median follow-up time was 7.6 years (aIBD) and 8.9 years (pIBD). In CD, 9% aCD and 24% pCD (P < 0.0001) patients had involvement of the upper GI tract (L4a or L4b either alone or in combination with L1-L3). At diagnosis, 22% and 12% of aCD and pCD, respectively, had non-inflammatory behavior and at end of follow-up this increased to 37% and 48%, respectively (P = 0.04). 24% and 66% of aUC and pUC, respectively, had extensive disease (E3) at diagnosis (P < 0.0001). A total of 14% and 42% of aIBD and pIBD patients, respectively, were treated with anti-TNF-alpha (HR: 3.2 (2.4–4.4), P < 0.0001) during follow-up. The increased risk was independent of IBD diagnosis and disease extent. In UC, 41% and 74% of aUC and pUC, respectively received either azathioprine or 6-mercatopurine (IM) during follow-up (HR 3.8 (2.8–5.2), P < 0.0001). This increased risk in pUC was independent of disease extent. Over the first 7 years after diagnosis pIBD patients had an increased risk of relapse compared to aIBD patients IRR 1.8 (CI 1.4–2.2), P < 0.0001. The increased risk of relapses persisted when adjusting for IBD diagnosis and extension. At end of follow-up bowel resection occurred in 18% and 29% of aIBD and pIBD, respectively, resulting in a hazard ratio of 1.4 (CI 0.97–2.0) and 0.9 (CI 0.5–1.7), P = 0.07 in CD and UC, respectively.

CONCLUSION(S):
PIBD patients had more extensive disease than aIBD patients, were more often treated with immunomodulators and biologic agents and had an increased risk of relapse. Moreover, pCD patients more often developed non-inflammatory behavior and a trend towards increased risk of surgery was noted. Compared to previous results this population-based cohort study demonstrated a clearly more severe disease course in pIBD than in aIBD. Consequently, pIBD patients must be monitored intensively and the top-down treatment protocol should be investigated for pIBD. As a future consequence of the severe disease course and frequent use of immunosuppressive medicine, attention should be paid towards the possible increased cancer risk in these patients.