Prevalence, characteristics, management, and outcomes of difficult-to-treat inflammatory bowel disease

Background and aim: Criteria for "difficult-to-treat" Inflammatory Bowel Disease (IBD) (DTT-IBD) have recently been proposed to standardize terminology. We aimed to evaluate the prevalence, characteristics, management, and outcomes of DTT-IBD.

Methods: We conducted a retrospective study in two tertiary centers in Italy.

Results: Among 1736 IBD patients treated with biologics/advanced small molecules, 430 (24.8%) met at least one DTT-IBD criterion, of which 331 (77%) failed at least 2 mechanisms of action.In ulcerative colitis (UC), left-sided and extended colitis were risk factors for DTT compared to proctitis (OR 6.55, 1.93-40.98, p=0.011; and OR 10.12, 3.01-63.14, p=0.002, respectively). In Crohn's disease (CD), multiple localizations (L3+L4) (OR 3.04, 1.09-8.34, p=0.03), stricturing (OR 2.24, 1.52-3.34, p<0.001) and penetrating (OR 2.33, 1.55-3.53, p<0.001) behaviors, and perianal disease (OR 2.49, 1.75-3.53, p<0.001) were the main risk factors for DTT.Delay in advanced treatment initiation was positively associated with DTT-CD (OR 1.74, 1.27-2.41 p=0.001) but protective in UC (OR 0.65, 0.45-0.93 p=0.019).The rates of symptomatic, biochemical, and endoscopic remission were lower in DTT-IBD compared to non-DTT-IBD. The difference was most evident for endoscopic remission (25% vs 62%).Drug persistency in each following line of treatment progressively decreased in CD and UC. All advanced drugs used in DTT-IBD had similar persistence.

Conclusions: DTT-IBD was prevalent in approximately one-quarter of patients with IBD in a tertiary care setting. Certain IBD phenotypes and the delay in initiating treatment in CD were risk factors for DTT. Drug persistency decreased progressively with every subsequent line of therapy.