Introduction
Clinical and radiologic factors associated with perianal fistula (PAF) healing in Crohn’s disease (CD) are poorly understood. We aimed to create a risk assessment model (RAM) to predict anti-TNF treatment failure in patients with PAF.
Aims & Methods
We performed a multicenter retrospective cohort study between 2005 and 2021. We included biologic naïve adults (>17 years) with CD who initiated anti-TNF therapy for active PAF after undergoing an MRI pelvis. Our primary outcome was treatment failure at 6 months defined clinically as ongoing PAF drainage. Pre-treatment MRI studies were prospectively re-evaluated centrally by radiologists blinded to clinical outcomes. Variables with p-values <0.1 on univariable analysis were included in our overall RAM and a simplified version consisting of MRI variables alone. Model performance was determined by calculating the area under the receiver operating characteristics curve (AUC) and internally validated using bootstrap methods. Our RAMs were compared with MAGNIFI-CD and modified Van Assche MRI scores (mVAS) by the De Long test. Aggregate scores from weighted variables from our simplified model were divided into tertiles to predict low, moderate and high risk of anti-TNF treatment failure.
Results
Our analysis included 221 patients: 133 (60%) males; mean age 29 years (SD, 21-42); 158 (71%) treated with infliximab and 70 (32%) treated with adalimumab. Treatment failure occurred in 102 (46%) patients. Our overall RAM included 3 clinical characteristics (age at fistula diagnosis, time to initiate biologic therapy and current smoking) and 8 MRI characteristics (non-inter/transsphincteric fistula anatomy, fistula length >4.3cm, primary tracts >1, secondary tracts >1, number of external openings, tract hyperintensity on T1 weighted imaging, horseshoe anatomy, and collections >1.3 cm). Our adjusted overall RAM and simplified MRI version were accurate in predicting fistula healing (AUC (95% CI), 0.75 (0.69-0.82) and 0.73 (0.66-0.79) respectively) (Table 1). The overall and simplified MRI RAMs performed significantly better than MAGNIFI-CD (p = 0.0002 and 0.0005) and the mVAS (p <0.0001 and <0.0001) respectively at predicting anti-TNF treatment failure. Aggregate scores for the simplified MRI RAM ranged between 0-30. Scores of 0-10, 11-20 and 21-30 were associated with treatment failure in 19%, 45% and 71% of patients respectively.
Table 1: Discriminatory capacity of risk assessment models for predicting anti-TNF treatment failure of perianal fistulas
|
|---|
| Model | AUC (95% CI) | Bootstrap validation C-statistic (RMSE) |
| Overall model | 0.75 (0.69-0.82)
| 0.67 (0.07)
|
| MRI model | 0.73 (0.66-0.79)
| 0.65 (0.07)
|
| MAGNIFI-CD | 0.61 (0.53-0.68)
| NA |
| Modified Van Assche score | 0.58 (0.51-0.66)
| NA |
Conclusion
In our multicenter study, we developed RAMs consisting of clinical and/or radiologic variables that can accurately predict treatment failure in patients with PAF. These findings may have important implications in clinical study design to help balance cohorts, and in clinical practice to help set realistic expectations of PAF healing for patients and providers.
Disclosure
Jeffrey McCurdy has received consultancy fees and/or speaker honoraria from Janssen, Abbvie, BMS, Fresenius Kabi, Takeda, and Pfizer.