Abstract
Perianal fistulizing Crohn’s disease (pfCD) presents a complex challenge, requiring precise endpoints in clinical trials to assess the efficacy of medical and surgical therapies. Magnetic Resonance Imaging (MRI) is the gold standard for evaluating fistula healing; however, variability in radiological definitions of fistula improvement and healing has hampered clinical trial design and real-world therapy effectiveness analyses. This study aimed to establish an international consensus on the definition of radiological healing in pfCD.
The study was conducted in two phases through the Treatment Optimisation and CLASSification of perianal Crohn’s Disease (TOpCLASS) consortium (Figure 1). Phase 1 involved a systematic literature review to identify MRI-based variables and indices used to define radiological healing in pfCD. The protocol was prospectively registered on PROSPERO (CRD42024504334). The methodological quality of these indices was assessed using the COSMIN framework, following PRISMA-COSMIN guidelines. This phase generated a comprehensive long list of relevant variables, which international experts assessed and refined during the Delphi process. Phase 2 utilized an online modified Delphi consensus process with international experts in pfCD. Two rounds of surveys were conducted, followed by a final stakeholder meeting to achieve consensus. An agreement threshold of >80% was set for consensus items, and results were reported per Accurate Consensus Reporting Document (ACCORD) guidelines.
Eighty-four international experts from 16 countries participated in the modified Delphi process with key findings in Figure 2. A strong consensus (>95%) was reached, defining a radiologically healed fistula by the absence of T2-weighted hyperintensity and, when contrast is used, the absence of contrast enhancement on post-contrast T1-weighted images. Radiological improvement of a fistula was defined (80% consensus) by an unequivocal reduction in one or more of the following: T2-weighted hyperintensity, fistula diameter, length, abscess size; or a predominantly fibrous fistula tract. An unequivocal reduction in hyperintensity of the fistula tract on contrast-enhanced T1-weighted images also indicated improvement. Other key findings on the timing of MRIs with surgery and/or advanced therapy usage as well as MRI sequences, timing and need for central reading are shown in Figure 2.
This internationally modified Delphi consensus is a major step toward standardizing radiological endpoints in pfCD. Adoption of this consensus definition will enhance the consistency and reliability of pfCD assessments in both clinical care and research settings. Future studies are underway to validate this definition and assess how changes in variables predict long-term clinical outcomes and improvements in quality of life.
Figure 1. Study Flowchart
Figure 2. Key findings
