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P512 Safety of reduced clinical monitoring in patients with stable Inflammatory Bowel Disease on maintenance thiopurine therapy

Jansen, F.M.(1);Smits, L.S.(1);Thomas, P.W.A.(1);den Broeder, N.(1);de Jong, D.J.(1);van Dop, W.A.(1);Hoentjen, F.(1);

(1)Radboud University Medical Centre, Gastroenterology and Hepatology, Nijmegen, The Netherlands

Background

Thiopurine-treated inflammatory bowel disease (IBD) patients are monitored every 3 to 4 months with outpatient visits and laboratory assessments to evaluate disease activity and safety of therapy. However, the risk of thiopurine-related adverse events decreases after the initiation phase. The aim of this study was to assess the safety of reduced clinical monitoring in steroid-free quiescent IBD patients on stable maintenance thiopurine monotherapy.

Methods

This single-centre prospective cohort study evaluated a reduced monitoring strategy that involved 6-monthly laboratory assessment combined with alternating outpatient and phone appointments, during 104 weeks. We enrolled IBD patients who were in steroid-free remission > 6 months on thiopurine monotherapy including azathioprine, 6-mercaptopurine or tioguanine. The primary outcome was thiopurine-related adverse events (AE) requiring change or discontinuation of thiopurine therapy after 104 weeks of follow-up. Secondary outcomes were assessed at week 52 and included other thiopurine-related AEs and laboratory abnormalities.

Results

We included 85 patients (42 years median age, 61.2% Crohn’s disease, 62% female) with a median disease duration of 12.5 years. At baseline, 47 patients were treated with azathioprine (55.3%), 25 with 6-mercaptopurine (29.4%) and 13 with tioguanine (15.3%) for a median duration of 6.7 years. During 104 weeks of follow-up, thiopurine therapy was ceased in two patients because of multiple infections (n=1) and gastrointestinal complaints (n=1). Other reasons for thiopurine cessation (n=37) were stable remission (n=26), patient preferences (n=9) and high 6-TGN levels (n=2). In total, 20 patients underwent thiopurine dose adjustments due to high metabolite levels (n=9), remission (n=3), disease flare (n=3), patient preferences (n=3), and low metabolite levels (n=2). At 52 weeks, 27 laboratory abnormalities were observed, yet none required therapy adjustments. In 13 patients (15.3%) myelotoxicity was detected, including mild leukopenia (n=11), mild and moderate thrombopenia (n=2). In 16.5%, hepatoxicity was observed (n=14) including mild (n=9) and moderate (n=1) elevated aspartate aminotransferase and mild elevated alkaline phosphatase (n=4).

Conclusion

A reduced monitoring strategy appeared relatively safe in a strictly selected cohort of stable thiopurine-treated IBD patients. Overall, two patients had to cease thiopurine therapy due to thiopurine-related AEs independent of monitoring frequency. No laboratory abnormalities required therapy adjustments and 57.1% of patients continued therapy throughout 104 weeks of follow-up. This strategy may contribute to safe reduction of time and health care costs for both IBD patients and physicians in daily IBD practice.

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