Withdrawal of long-term maintenance treatment with azathioprine tends to increase relapse risk in patients with Crohn's disease.

Background And Aim: Many patients with quiescent Crohn's disease are maintained on long-term treatment with azathioprine (AZA), but controlled data are limited. We aimed to evaluate the efficacy of AZA therapy for more than 4 years to maintain clinical remission.

Methods: We performed a randomized double-blind placebo-controlled AZA withdrawal trial with a follow-up period of 24 months. Patients had to have continuous AZA therapy ≥ 4 years without exacerbation of disease during the 12 months before enrollment, and a Crohn's disease activity index < 150 at baseline. Patients were randomized to continue on AZA or switch to placebo. The primary endpoint was time to clinical relapse during follow-up.

Results: After inclusion of 52 patients, the trial was stopped prematurely due to slow recruitment. During the 2-year follow-up, clinical relapse occurred in 4 of 26 (15 %) patients on continued AZA and in 8 of 26 (31 %) patients on placebo. Time to clinical relapse averaged 22.3 months (95 % CI 20.6-24.0) on AZA and 19.2 months (95 % CI 16.4-22.1) on placebo (p = 0.20). According to life-table analysis, the proportion of patients in remission after 12 and 24 months was 96 ± 4 and 86 ± 7 % in patients receiving AZA versus 76 ± 8 and 68 ± 9 % in patients receiving placebo (month 12, p = 0.035; month 24, p = 0.30). A higher AZA dose at enrollment was an independent predictor for relapse (p < 0.05).

Conclusions: AZA withdrawal resulted in a significantly increased relapse risk after 1 year and a nonstatistically significant trend for relapse after 2 years. Our results are in line with previous observations.