STUDY OF THE ADDED VALUE OF A TRANSMURAL EVALUATION IN PATIENTS WITH CROHN'S DISEASE UNDER BIOTHERAPY WITH CLOSE FECAL CALPROTECTIN FOLLOW-UP

This is a randomized, open-label controlled study comparing two therapeutic strategies in patients with CD (see inclusion criteria) starting biotherapy. Randomization, by minimization (Stata version 15), will be stratified by center, by biotherapy line and on the location of the disease: MC colic isolated (L2 according to the Montreal classification) vs. Ileal or ileocolic MC (L1 + L3), for a maximum of L1 + L3 patients of 70%. The reference arm will be based on that of the CALM study, i.e. regular follow-up (S0, S12, S24, S52, S76, S100, S124 and S152) with therapeutic intensification in the absence of at least one criterion among CDAI \<150, CRP \<5 or fecal calprotectin \<250. After checking the inclusion criteria, the patients will be included and randomized. The initial choice of biotherapy, therapeutic intensifications (dose increase, interval reduction, treatment change) and treatment sequences will be based on the French consensus of 2020. MRI will be performed in all patients at weeks 0, 76 and 152. In the MRI arm, an additional MRI will be performed at W24 and W52 with therapeutic intensification at W24, W52 and W76 in the presence of residual MRI activity. Patients will be followed for 152 weeks (≈ 3 years). In the event of a missing examination (calprotectin or MRI), the intensification will be carried out or not with the available data. Therefore, the analysis will be performed by intention to treat (ITT). Patients will be given a symptom calendar (abdominal pain score (between 0 = no pain and 3 = severe pain) and number of stools). Each month without data (lost to follow-up) will be considered as in the absence of clinical remission without corticosteroids (ITT). The fecal calprotectin dosage will be standardized and performed with the same test in all patients. Therapeutic intensification based on MRI will be carried out after a centralized review. The secondary endpoints (response and transmural healing, Lémann index) will be centrally blinded in the study arm to avoid any evaluation bias.