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.