Lower Risk of B1-to-pB3-Stage Migration in Crohn's Disease Upon Immunosuppressive and Anti-TNF Treatment in the Swiss IBD Cohort Study.

While the long-term evolution of disease behavior in Crohn's disease has been well described in the pre-anti-TNF era, our knowledge thereon remains scarce after the introduction of anti-TNF. Our investigation examined the long-term evolution of disease concerning Montreal classification's B-stages over time in patients enrolled into the Swiss IBD Cohort Study between 2006 and 2017. We analyzed prospectively collected SIBDCS data using a Markov model and multivariate testing for effects of treatment and other confounders on B-stage migration over time. The primary outcome was a transition in disease behavior from B1 to either B2 or pB3, or from B2 to pB3, respectively. The 10- and 15-year probability of remaining in B1 was 0.61 and 0.48, as opposed to a probability to migrate to B2 or B3 of 0.25 or 0.14, and 0.32 or 0.2, after 10 and 15 years, respectively. In multivariate testing, the hazard ratio for migrating from B1 to pB3 (HR 0.27) and from B2 to pB3 (HR 0.12) was lower in patients > 40 years compared to patients < 17 years. We found that immunosuppression (HR 0.38) and treatment with anti-TNF for > 1 year (HR 0.30) were associated with a decreased likelihood of transitioning from stage B1 to pB3. While in the anti-TNF era most patients with Crohn's disease will eventually develop stricturing and/or penetrating complications, our data indicate that immunosuppressive and anti-TNF treatment for more than 1 year reduce the risk of transitioning from stage B1 to pB3 in the long-term run