Introduction Thiopurine therapy is effective in maintaining clinical remission in IBD. However, long-term therapy is associated with an increased risk of lymphoma; therefore in clinical practice we aim to withdraw therapy after 4–5 years. Nevertheless, many patients will experience disease relapse within 12 months of drug withdrawal.¹

Methods The aim of the present study was to retrospectively determine the relapse rate in ulcerative colitis (UC) and Crohn's disease (CD) following azathioprine (AZA) or mercaptopurine (MP) withdrawal and to determine factors predictive of relapse. Patients were identified by electronic case note review of an IBD research database in Edinburgh. Major inclusion criteria were AZA and/or MP therapy for a minimum of 3 years, AZA/MP withdrawn due to sustained clinical remission no steroid therapy for 6 months prior to drug withdrawal, and minimum 12 months follow-up. The primary outcome was disease relapse requiring AZA reinitiation, steroids or colectomy within 12 months of AZA/MP withdrawal, with secondary outcome assessed at 24 months. Clinical/laboratory predictors of relapse were sought. 1826 electronic records were reviewed (865 CD and 961 UC). 634 were treated with a thiopurine (348 CD and 286 UC). 74 met the strict study inclusion criteria (45 CD and 29 UC).

Results CD was associated with a significantly higher risk of relapse than UC on Kaplan–Meier analysis (Abstract OC-166 figure 1, p=0.026). The moderate-severe relapse rate for 12 months was 44% for CD and 14% for UC. For 24 months, relapse rates were 60% for CD and 48% for UC. Elevated platelet count (p=0.03) and elevated white cell count (p=0.03) were predictive of relapse for UC, while no predictive factors were identified for CD. Median (range) duration of thiopurine use was 6.2 (3.4–18.7) years for CD and 6.0 (3.1–18.0) years for UC. Median duration of follow-up was 32 months for CD and 45 months for UC. Retreatment with a thiopurine after relapse was successful in 7/7 cases for UC and 18/24 for CD.

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Abstract OC-166 Figure 1

Survival curves for moderate to severe relapse following thiopurine withdrawal in Crohn's disease and ulcerative colitis

Conclusion Relapse rates after withdrawal of a thiopurine are high, particularly for CD, and predicting this remains difficult. To help increase the power of this study, we are now expanding it across the UK.

Competing interests None declared.

Reference 1. Treton. Clin Gastroenterol Hepatol 2009;7:80.