Effectiveness of Early Thiopurine Use in Korean Patients With Moderate-to-Severe Ulcerative Colitis: A Prospective Multicenter Cohort (MOSAIK) Study

Background: Thiopurines play an important role in the management of steroid-refractory and steroid-dependent ulcerative colitis. However, the effectiveness of the early use of thiopurines in ulcerative colitis remains controversial. Materials and Methods: In this multicenter prospective cohort (MOSAIK) study, we divided patients with ulcerative colitis into those who underwent early (within 6 mo of diagnosis) and late (6 mo after diagnosis) thiopurine therapy to determine the effectiveness of early thiopurine treatment. The primary outcome was the cumulative rate of clinical relapse (Mayo score >2 points). Multivariate Cox proportional hazards regression was used to identify independent clinical factors associated with the outcomes. Results: Overall, 333 patients with moderate-to-severe ulcerative colitis were included. Of the 118 patients treated with thiopurines, 65 (55.1%) and 53 (44.9%) received thiopurine therapy within and after 6 months of diagnosis. The cumulative use rate of thiopurines was 38.9% at 3 years after diagnosis. The median initial dose of thiopurines was 0.7 mg/kg (0.3 to 2.0); the median maintenance dose was 1.1 mg/kg (0.3 to 2.4). The cumulative rate of clinical relapse was not significantly different between patients who started thiopurine therapy within 6 months of diagnosis and those who started therapy 6 months after diagnosis (P=0.712). The presence of extraintestinal manifestations (hazard ratio: 4.674, 95% CI: 1.210-18.061, P=0.025) independently predicted an increased risk of clinical relapse. Conclusions: Patients with ulcerative colitis who received early thiopurine therapy did not differ significantly in terms of clinical relapse compared with those who received late therapy.