P298 Wall thickness ratio, a new magnetic resonance parameter, predicts the outcome of biological therapy in patients with ileal and ileocolonic Crohn’s disease

Abstract

Magnetic resonance enterography (MRE) is a non-invasive useful tool for assessing the transmural and extraintestinal lesions in Crohn's disease (CD). The absolute measure of transmural healing (TH) has been recently associated to improved long-term outcome in CD. However, a not negligible proportion of patients responding to biological therapy does not achieve TH. The aim was to identify a new MRE parameter assessing clinical outcome of biological therapy in patients with active ileal or ileocolonic CD. Consecutive patients with ileal or ileocolonic involvement, attending our IBD unit and scheduled for anti-TNF (Infliximab, Adalimumab) or anti-integrin therapy (Vedolizumab), were enrolled. All patients underwent MRE at baseline (T0) and after 1 year (T1). CRP and Harvey–Bradshaw index (HBI) were measured at T0, T1, and after 2 years of treatment (T2). Non-response to therapy was defined at T2 as: <3-point change in HBI (T0-T2), need for steroids, optimisation/change of treatment or surgery. TH, defined as wall thickness ≤3 mm without ulcers, oedema, enhancement and complications, was evaluated by MRE at T1. Wall thickness ratio (WTR) was calculated as wall thickness (mm) at T1/wall thickness at T0. A total of 103 patients were enrolled: 56 were responders and 47 non-responders to biological therapy after 2 years of treatment. The median (±interquartile range) values of CRP and HBI were 15.0 mg/l [2–19] and 8.27 mg/l [6–10] at T0, 8.92 mg/l [1–4] and 4.95 [2–7.5] at T1 and 3.73 mg/l [1–4.5] and 4.54 mg/l [2–7.25] at T2. Overall, 16 out of 56 responders and 3 out of 47 non-responders achieved TH (28% and 6%, respectively, p < 0.01). Mean (±SD) WTR was 0.64 ± 0.23 in responders and 0.97 ± 0.26 in non-responders. According to the upper value of 95% confidence interval in non-responders, the WTR cut-off value of 0.87 was calculated. Therefore, 44 (78%) responders had a WTR < 0.87 and 20 (74%) non-responders had a WTR >0.87. In the group of responders, the proportion of patients with a WTR <0.87 was significantly higher than the proportion of patients achieving TH (78% vs. 28%, p < 0.01). The presence of a WTR <0.87 at T1 was significantly associated to a response to biological therapy at T2 (RR 3.6, 1.7–7.2) with a sensitivity of 74% and a specificity of 77%. Positive and negative predictive values were 71% and 80%, respectively. Wall thickness ratio appears to be a useful MRI variable as it discriminates responders to biological therapy, also in patients not achieving transmural healing. This novel variable accurately predicts a favourable response to biological therapy in CD patients and may be considered a useful parameter for monitoring patients during therapy.