DOP11 Fibrosis and MAGNIFI-CD activity-index at MRI to predict treatment outcome in perianal fistulising Crohn’s Disease patients

Background and aims Characteristic MRI features associated with long-term perianal fistula closure are still being discussed. This study evaluated the predictive value of degree of fibrosis and disease activity (MAGNIFI-CD index) at MRI for long-term clinical closure of Crohn's perianal fistulas. Methods Crohn's disease (CD) patients treated with surgical closure following anti-TNF induction or anti-TNF alone for high perianal fistulas as part of a patient preference RCT (PISA-II) between 2013-2020 with a post-treatment MRI and long-term clinical follow-up data were retrospectively included. Two radiologists scored the degree of fibrosis and MAGNIFI-CD index at pre- and post-treatment MRI. The accuracy of post-treatment MRI findings in predicting long-term clinical closure (12 months after the MRI) was evaluated using receiver operating characteristics (ROC) analysis. Results Fifty patients were included; 31 female, median age 33 years (IQR 26-45). Fourteen patients showed a 100% fibrotic fistula at post-treatment MRI, all of which had long-term clinical closure. Median MAGNIFI-CD index at post-treatment MRI was 0 (IQR 0-5) in 25 patients with long-term clinical closure and 16 (IQR 10-20) in 25 patients without. ROC analysis showed an area under the curve of 0.90 (95%-CI 0.82-0.99) for degree of fibrosis and 0.95 (95%-CI 0.89-1.00) for the MAGNIFI-CD index, Youden cut-off point of six (91% specificity, 87% sensitivity). Conclusions Degree of fibrosis and MAGNIFI-CD index at post-treatment MRI are accurate in predicting long-term clinical closure and seem valuable in follow-up of perianal CD. A completely fibrotic tract at MRI is a robust indicator for long-term fistula closure.