Background: Immunomodulator monotherapy is an important component in the treatment of inflammatory bowel disease (IBD). However, there is conflicting literature about thiopurines maintaining long-term remission in patients with active IBD.
Aim: To determine the durable clinical remission rate in adults with Crohn's disease (CD) or ulcerative colitis (UC) on thiopurine monotherapy over 5 years.
Methods: We performed a retrospective analysis of adult patients identified at McGill University Health Centre from 2009 to 2012. We included IBD patients who initiated thiopurine monotherapy and were in remission for at least 3 months (Harvey-Bradshaw Index (HBI) < 5 points for CD and partial Mayo Score (pMS) < 2 points in UC). The primary endpoint was sustained clinical remission on thiopurines during a 5-year follow-up. This included patients who had not relapsed or discontinued the drug due to side effects. The secondary endpoint was clinical relapse over the follow-up period, which was defined as HBI > 5 in CD and pMS > 2 in UC.
Results: There were 148 patients included in the study (100 CD; 48 UC). At 5 years, 23% (34/148) patients remained in clinical remission on thiopurine monotherapy (25 CD and 9 UC patients). Thirty-three percent (33/100) of CD and 46% (22/48) of UC patients relapsed while on thiopurines. There was no difference in relapse rates between CD and UC patients. Eighty-four percent (42/50) of patients with CD with side effects and all UC (17/17) patients who experienced side effects discontinued the drug.
Conclusion: This analysis demonstrates that there is poor sustainability of clinical remission in IBD patients on thiopurine monotherapy given that a high proportion of patients discontinue thiopurines due to either relapse or side effects.
Keywords: Inflammatory bowel disease; Relapse rates; Side effects; Thiopurine monotherapy.