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P287. Short and long-term effectiveness of azathioprine and mercaptopurine in patients with inflammatory bowel disease (IBD)

C. Castaño-Milla, M. Chaparro, J. Maté-Jiménez, J.P. Gisbert

Gastroenterology Unit. La Princesa University Hospital., Madrid, Spain

Objective: To evaluate the short and long-term effectiveness of thiopurine drugs in the treatment of IBD. To identify predictors of initial effectiveness and maintenance of long-term remission. To evaluate the safety of treatment with thiopurine drugs.

Methods: A cohort of patients diagnosed with Crohn's Disease (CD) or Ulcerative Colitis (UC) who had ever been on thiopurine therapy due to the IBD were retrospectively analyzed. For UC patients, response was considered as a decrease of at least 3 points in the Partial Mayo Index; for CD patients, response was defined either as a decrease of at least 4 points in the Harvey-Bradshaw Index in patients with luminal CD or as a reduction of at least 50% in the number of fistulae with drainage openings in patients with fistulizing perianal CD. Short-term effectiveness was evaluated 12 months after starting thiopurine treatment. Long-term response maintenance was estimated using Kaplan–Meier analysis. Cox-regression analysis was performed to identify potential predictive factors for loss of response. Analysis was performed both by intention-to-treat (ITT) and per-protocol (PP) analysis. The ITT analysis considered all the patients for the short-term effectiveness and only those who continued treatment beyond 12 months for the long-term effectiveness. The PP analysis only included the patients who did not discontinue the treatment due to adverse effects and received the treatment for at least four months in the short-term effectiveness, and for at least 12 months in the long-term effectiveness.

Results: 309 patients who had ever been on thiopurine therapy were included. The mean age was 43 years, 51% were men, and 74% were diagnosed with CD. The overall short-term effectiveness was 81.9% (95% CI, 77–86%) in the ITT analysis, and 96.2% (93–98%) in the PP analysis. In the multivariate analysis there was not any predictive factor associated with a higher response to these drugs, including the type of IBD (UC vs. CD). 243 patients continued treatment beyond 12 months, and they were considered for the long-term effectiveness analysis. The probability of maintaining response was 95.9% (93–98%) at 24 months of starting treatment, 92.8% (89–96%) at 36 months, and 89.4% (85–93%) at 48 months in the ITT analysis. In the PP analysis, the probability of remaining free of disease relapse with immunosuppressive therapy was 95.9% (93–98%) at 24 months of starting treatment, 92.8% (89–96%) at 36 months and 89.4% (85–93%) at 48 months. Predictive factors associated with the maintenance of response in the long-term were not identified in the multivariate analysis. 17% of patients suffered adverse effects related to thiopurine treatment, and finally 9.7% discontinued treatment because of this. The most frequent adverse effect was the gastrointestinal intolerance (5.5%).

Conclusions: The effectiveness of thiopurines for the treatment of IBD is acceptable, in the short and in the long-term. Predictors of response to thiopurines were not found, with similar responses rates among CD and UC patients. Thiopurines are relatively safe, both in the short and in the long-term.