Efficacy of Dose Escalation of Oral 5-Aminosalicylic Acid for Ulcerative Colitis With a Mayo Endoscopic Subscore of 1: An Open Label Randomized Controlled Trial

Background: Endoscopic healing is generally defined as Mayo endoscopic subscore (MES) ≤1 in ulcerative colitis (UC). However, patients with an MES of 1 are at higher relapse risk than those with an MES of 0. This study evaluated the therapeutic efficacy of proactive dose escalation of oral 5-aminosalicylic acid (5-ASA) in UC patients with an MES of 1. Methods: An open-label, randomized controlled trial was conducted in 5 hospitals between 2018 and 2022. Ulcerative colitis patients in clinical remission under oral 5-ASA therapy and diagnosed as having an MES of 1 were enrolled. Patients receiving maintenance therapy other than 5-ASA and immunomodulator were excluded. Patients were randomly assigned in a 1:1 ratio to receive either a dose-escalated (intervention) or constant dose (control) of 5-ASA. Concomitant immunomodulator was used as the stratification factor in the randomization. The primary end point was relapse within 1 year. The subgroup analysis was stratified for the use of immunomodulators. Results: The full analysis set included 79 patients (39 intervention and 40 control). Immunomodulators were used in 20 (25.3%) patients. Relapse was less in the intervention group (15.4%) than the control group (37.5%; P = .026). In the subgroup with concomitant immunomodulators, relapse was also less in the intervention group (10.0%) than the control group (70.0%; P = .020). In patients without immunomodulators, the difference was not significant between 2 groups (intervention, 17.2%; control, 26.7%; P = .53). Conclusions: Dose escalation of 5-ASA reduced relapse within 1 year in UC patients in clinical remission with an MES of 1.