Early tumour necrosis factor antagonist treatment prevents perianal fistula development in children with Crohn's disease: post hoc analysis of the RISK study.

Background: One in three children with Crohn's disease develop perianal fistula complications (PFCs), among the most disturbing and difficult-to-treat disease-related complications. Retrospective evidence suggests PFCs may be preventable.

Objective: We aimed to determine if early antitumour necrosis factor-alpha (anti-TNF⍺) therapy prevents PFC development in a well-characterised prospective cohort of paediatric patients with Crohn's disease who were free from PFC at enrolment.

Design: RISK was a multicentre inception cohort of children newly diagnosed with Crohn's disease. We included all patients who had never experienced PFCs 30 days after study enrolment. We conducted nearest-neighbour propensity score-matched triad analyses. Matching was performed to balance patient characteristics across three mutually exclusive treatment groups based on therapy prior to either PFC development or the end of the observation period.

Results: Among 873 patients without perianal fistula, 447 matched patients were included (149 per treatment group). The presence of non-penetrating perianal lesions (large skin tags, ulcers and/or fissures) was significantly associated with PFC development, with 4-fold greater odds of PFC (OR 4.08, 95% CI (95% CI) 1.70 to 9.78; p=0.0016). Early anti-TNF⍺ therapy was associated with an 82% decrease in the odds of PFC (OR 0.18, 95% CI 0.05 to 0.66; p=0.01). Among those with perianal lesions, anti-TNF⍺ therapy was associated with 94% reduced odds of PFC development (OR 0.055, 95% CI 0.006 to 0.50; p=0.010). No other treatment group was associated with reduced risk of PFC.

Conclusion: Early anti-TNF therapy prevents perianal fistula development, especially among patients at increased risk.