One-year clinical outcomes with biologics in Crohn's disease: transmural healing compared with mucosal or no healing.

Background: While mucosal healing has been proved to predict relevant clinical outcomes in Crohn's disease (CD), little is known about the long-term significance of transmural healing. Aims: To prospectively assess the 1-year clinical outcomes in CD patients achieving transmural healing following treatment with biologics, and to compare them with those in patients reaching only mucosal healing or no healing. Methods: Observational longitudinal study, evaluating 1-year outcomes in terms of steroid-free clinical remission, rate of hospitalisation and need for surgery in a group of CD patients treated with anti-tumour necrosis factor (TNF) alpha for 2 years. Bowel sonography was used in all patients to determine transmural healing. Results: Of 218 patients who completed a 2-year treatment course with anti-TNF alpha, 68 (31.2%) presented transmural (plus mucosal) healing (bowel wall thickness ≤3 mm at bowel sonography), 60 (27.5%) mucosal healing only, and 90 (41.3%) did not achieve any intestinal healing. Transmural healing was associated with a higher rate of steroid-free clinical remission (95.6%), lower rates of hospitalisation (8.8%) and need for surgery (0%) at 1 year compared to mucosal (75%, 28.3% and 10%, respectively) and no healing (41%, 66.6% and 35.5%, respectively) (P < 0.001). Furthermore, transmural healing was associated with longer intervals until clinical relapse (HR, hazard ratio 0.87, P = 0.01), hospitalisation (HR 0.88, P = 0.002) and surgery (HR 0.94, P = 0.008) than mucosal healing. Also among patients discontinuing treatment with biologics, transmural healing predicted better clinical outcomes at 1 year than mucosal healing (P = 0.01). Conclusions: Transmural healing is an ambitious and powerful treatment goal associated, to a greater extent than mucosal healing, with improvement of all clinical outcomes. Additionally, transmural healing is associated with better long-term clinical outcomes than mucosal healing also after discontinuation of biologics.