Clinical and radiological responses after infliximab treatment for perianal fistulizing Crohn's disease

OBJECTIVES: Infliximab is an effective therapy for fistulizing Crohn's disease of the perineum. We sought to determine whether the clinical improvement after infliximab is associated with radiological closure of fistula tracts. METHODS: Clinical responses and radiological imaging studies by transperineal ultrasound were evaluated in 35 patients with Crohn's disease perianal fistulas after treatment with infliximab 5 mg/kg up to 48 wk. Paired comparison of baseline and follow-up imaging studies at 8 wk and at 56 wk or discontinuation were assessed by an imaging score of perianal fistula severity, based on the Parks criteria. Complete clinical fistula closure and radiological healing were primary outcome measures. RESULTS: At 8 wk, after two infusions of infliximab at 0 and 2 wk, clinical fistula closure occurred in 49% of patients. The radiological score at 8 wk was higher for patients with clinical fistula closure than for patients with no clinical improvement (p= 0.023) and two patients showed complete radiological healing. At 56 wk, clinical fistula closure occurred in 46% patients. Clinical fistula scores correlated with radiological scores (R2= 0.52; p < 0.001) but were not associated with fistula complexity, number of fistulas, or number of collections at baseline imaging. The proportion of patients with marked radiological improvement increased from 14% at 8 wk to 43% at 56 wks (p= 0.015) and complete radiological healing occurred in 4 (11%) patients. CONCLUSIONS: For perianal fistulizing Crohn's disease, repeat dose infliximab improves clinical and radiological outcomes, although complete radiological healing occurs in a minority of patients.