Modeling Endoscopic Improvement after Induction Treatment With Mesalamine in Patients With Mild-to-Moderate Ulcerative Colitis

Background & Aims: Endoscopic improvement is an important treatment target for mild-to-moderate ulcerative colitis (UC). However, early endoscopic evaluation is not always feasible. We aimed to develop a clinical decision support tool to discriminate patients who have achieved endoscopic improvement from those with more severe inflammation following mesalamine induction therapy. Methods: We performed a post-hoc analysis of data from a phase 3 non-inferiority trial of 726 adults with mild-to-moderate UC treated with mesalamine. Multivariable logistic regression modeling determined associations between candidate variables and endoscopic improvement (Mayo endoscopic subscore=0-1 according to blinded central reading) at Week 8. Internal model validation was performed using bootstrap resampling. A clinical decision support tool was developed to stratify patients into low, intermediate, and high probability groups for endoscopic improvement. Results: Variables associated with endoscopic improvement at Week 8 included 50% reduction in fecal calprotectin from baseline (odds ratio [OR] 2.64, 95% CI:, 1.81, 3.85), reduction in rectal bleeding (OR 1.79 per point reduction, 95% CI: 1.35, 2.39), and improvement in physician global assessment (OR 2.32 per point improvement, 95% CI: 1.88, 2.85). The baseline Geboes score (OR 0.74 per grade, 95% CI: 0.65, 0.85) and prolonged disease duration (OR 0.95 per year, 95% CI: 0.92, 0.98) were negatively associated with endoscopic improvement. This model strongly discriminated endoscopic improvement in the development dataset (area under the curve [AUC] 0.84, 95% CI: 0.81, 0.87) and during validation (AUC 0.83). Conclusions: We developed and validated a clinical decision support tool that has good discriminative performance for induction of endoscopic improvement in patients with mild-to-moderate UC treated with mesalamine. ClinicalTrials.gov Registration: NCT01903252.