Azathioprine Withdrawal Is Cost-Effective in Patients with Crohn's Disease in Remission on Infliximab and Azathioprine.

Background: In Crohn's disease, combination therapy with infliximab and azathioprine is more effective than either drug alone but is associated with a higher risk of therapy-related complications. Though therapy de-escalation can reduce risks and save costs, it is associated with a risk of Crohn's disease relapse.

Aims: We aimed to study the cost-effectiveness of de-escalation strategies in Crohn's disease patients in remission on infliximab and azathioprine.

Methods: We constructed a decision tree with Markov models for continuation of infliximab and azathioprine, discontinuation of azathioprine followed by its re-introduction in case of relapse, discontinuation of azathioprine followed by infliximab dose intensification without azathioprine reintroduction in case of relapse and discontinuation of infliximab. Third-party payers' perspective with a willingness-to-pay threshold of $100,000/quality-adjusted life years was used. Markov cycle length was 3 months, and the study period was 5 years. A 35-year-old patient with Crohn's disease in clinical remission on azathioprine 150 mg daily and infliximab 5 mg/kg every 8 weeks was used for base-case analysis.

Results: Azathioprine withdrawal followed by its reintroduction upon relapse was the dominant strategy as it was the most effective and least expensive approach on base-case analysis. It was also cost-effective in 99.3% of Monte Carlo trial simulations. AZA withdrawal without IFX dose intensification upon relapse was the least effective and the most expensive strategy.

Conclusion: Azathioprine withdrawal is the most effective and least costly de-escalation strategy in CD patients in remission on combination therapy if AZA re-introduction is performed upon CD relapse.