Supplementary Material for: Long-term outcomes and clinical factors associated with conventional therapy failure in intestinal Behçet’s disease: A retrospective cohort study in Japan

Background: We aimed to identify the long-term outcomes and predictive factors for failure of conventional therapy (CT), including 5-aminosalicylic acid, azathioprine, and glucocorticoid, in patients with intestinal Behçet's disease (i-BD). Methods: This retrospective study included 63 patients with i-BD receiving CT at the University of Tokyo Hospital between April 2005 and July 2024. Patients requiring anti-tumor necrosis factor-alpha (TNF-α) agents due to CT failure were categorized into the advanced therapy (AT) group, whereas those controlled with CT were classified as the CT group. Risk factors for CT failure were analyzed using Cox proportional hazards regression, and cumulative failure rates were using the Kaplan–Meier method. Results: Twenty-eight patients (44.8%) required AT during a median follow-up of 93 months. The cumulative 1-, 3-, 5-, and 10-year failure rates of CT were 22.6%, 35.9%, 40.0%, and 50.8%, respectively. Multivariate analysis identified maximum ulcer size ≥3 cm (hazard ratio [HR]: 2.68, 95% confidence interval [CI]: 1.05–6.84, p=0.030), concomitant proton-pump inhibitor (PPI) use (HR: 2.65, 95%CI: 1.06–6.58, p=0.036), C-reactive protein (CRP) ≥4 mg/dL (HR: 2.56, 95%CI: 1.04–6.31, p=0.042), and hematochezia (HR: 2.40, 95%CI: 1.05–5.46, p=0.037) as independent predictors of CT failure. A predictive model using all four factors demonstrated good accuracy (AUC=0.877) for predicting AT requirement. Regarding AT efficacy, 22 patients (78.6%) in the AT group continued AT for at least 1 year, with most achieving clinical and endoscopic remission. Concomitant glucocorticoid use significantly decreased from 12.7±11.7 mg/day at baseline to 2.4±2.5 mg/day at 1 year (p<0.001). Conclusions: Large ulcer size, PPI use, high CRP, and hematochezia are risk factors for CT failure. Anti-TNF-α agents are effective in patients with CT failure, and risk-based treatment strategies may improve disease control in patients with i-BD.