Purpose: This study was designed to evaluate the predictive factors of response of perianal Crohn's disease to azathioprine or 6-mercaptopurine.
Methods: Ninety-four patients (65 females; mean age, 31 years) with active perianal Crohn's disease were treated with azathioprine or 6-mercaptopurine for more than 6 (median, 27) months (median azathioprine dose, 2 mg/kg/day). The evolution of perianal lesions during azathioprine or 6-mercaptopurine therapy was analyzed retrospectively. Patients who had a clear anatomic improvement (fistula closure, fissure healing, stricture dilatation) and who did not develop any perianal complications requiring an antibiotic course or surgical intervention were considered responders regarding their perianal disease.
Results: Three years after inclusion, the cumulative probabilities of remaining free of perianal complication and achieving a clear anatomic improvement were 0.47 (95 percent confidence interval, 0.36-0.58) and 0.4 (95 percent confidence interval, 0.29-0.53), respectively. On the whole, 27 patients (29 percent) were responders to azathioprine or 6-mercaptopurine therapy. The absence of fistula, duration of perianal disease shorter than 22 months, and aged 40 years or older at inclusion were three independent factors associated with response to azathioprine or 6-mercaptopurine therapy. There was no correlation between the response of perianal lesions and the achievement of intestinal remission with azathioprine or 6-mercaptopurine.
Conclusion: One-third of patients with perianal lesions of Crohn's disease demonstrated a clear improvement during azathioprine or 6-mercaptopurine therapy. Patients aged 40 years or older with a recent perianal disease and without fistula were the best responders.