ADC Values for Detecting Bowel Inflammation and Biologic Therapy Response in Patients With Crohn Disease: A Post-Hoc Prospective Trial Analysis.

Background: New biologic agents for Crohn disease (CD) create a need for noninvasive disease markers. DWI may assess bowel inflammation without contrast agents. Objective: To evaluate ADC values for identifying bowel inflammation and therapeutic response in patients with CD treated with biologic therapy. Methods: This study entailed post-hoc analysis of prospective trial data. Analysis included 89 patients (median age, 37 years; 49 women, 40 men) with CD treated by biologic therapy who underwent MR enterography (MRE) at baseline and 46 weeks after therapy, from March 2013 to April 2021; 43 patients underwent ileocolonoscopy at both time points. Analysis was conducted at the level of small-bowel and colorectal segments (586 segments analyzed). Magnetic Resonance Index of Activity (MaRIA) score and presence of endoscopic ulcers were determined at both time points. One observer measured bowel-wall ADC. Diagnostic performance was evaluated. Dichotomous ADC assessments used threshold of 1301×10-6 mm2 /s based on initial ROC analysis; dichotomous MaRIA score assessments used threshold of 11 (moderate-to-severe inflammation). Second observer repeated ADC measurements in 15 patients. Results: At baseline, ADC had AUC of 0.92, sensitivity of 78.6%, specificity of 91.4%, and accuracy of 88.2% for detecting segments with MaRIA score ≥11. At baseline, AUC for detecting endoscopic ulcers was 0.96 for MaRIA score versus 0.87 for ADC (p<.001); sensitivity, specificity, and accuracy were 70.8%, 90.2%, and 85.1% for ADC, and 86.2%, 96.2%, and 93.6% for MaRIA score. At follow-up, ADC had AUC of 0.87, sensitivity of 75.4%, specificity of 83.6%, and accuracy of 80.0% for detecting improvement in MaRIA score to <11. At follow-up, AUC for detecting endoscopic ulcer healing was 0.94 for MaRIA score versus 0.84 for ADC (p<.001); sensitivity, specificity, and accuracy were 70.7%, 95.8%, and 84.4% for ADC, and 90.2%, 100.0%, and 95.6% for MaRIA score. Interobserver agreement for ADC, based on intraclass correlation coefficient, was 0.70 at baseline and 0.65 at follow-up. Conclusions: The findings do not support use of ADC rather than MaRIA scores for detecting biologic therapy response. Clinical Impact: ADC may have an adjunctive role in assessing bowel inflammation in CD, but showed limited performance for detecting biologic therapy response.