Bernd Bokemeyer

Credit: Interdisciplinary Crohn Colitis Centre Minden

A revision of the Montreal classification for Crohn’s disease could better capture patient complications to better align with the current state of inflammatory bowel disease (IBD) treatments.¹

A team, led by Bernd Bokemeyer, Interdisciplinary Crohn Colitis Centre Minden, examined the use of a bidirectional Montreal classification system that can capture disease regression in patients with Crohn’s disease.

Classification Systems

The Montreal classification allows a unidirectional assessment of the complications and behavior of Crohn’s disease, but does not allow for downstaging.

“Historically, the development of complications was seen as a unidirectional event because certain complications (e.g., destruction of anatomical structures) were considered irreversible,” the authors wrote. “However, advanced therapies including modern biologics may provide curative approaches to some of these complications (e.g., the use of stem cell-based therapies to heal fistula tracts or future therapies that target the reversal of fibrosis).”

Developed in 1998, the Montreal classification is commonly used to categorize the course of Crohn’s disease and is a revision of the Vienna classification, which is based on a trio of phenotype characteristics—age at diagnosis, disease location, and disease behavior.

In 2005, the system was updated to better classify patients with Crohn’s disease at the time of diagnosis, to allow for the co-classification of location L4 with locations L1-L3, and to include a modifier of B1-B3 behavior for perianal disease.

“Similar to the Vienna classification, the Montreal classification is based on a unidirectional hierarchy of disease evolution (inflammatory (B1) < stricturing (B2) < penetrating (B3)),” the authors wrote. “Therefore, according to this classification, once a patient reaches a “B2” or “B3” classification, this stage will be maintained throughout the entire course of disease. This underlying concept was adequate at a time when therapies could not reverse any of the complications of CD affecting organ structures.”

The Study

In the study, the investigators used data from the BioCrohn Registry, an inception cohort of patients with Crohn’s disease for at least 12 months that were followed-up with for up to 5 years.

The team estimated cumulative probabilities for developing complications using the Kaplan-Meier method and estimated potential associations of explanatory variables with disease progression using Cox regression.

The study included 393 patients with Crohn’s disease, of which 255 individuals completed the follow-up.

The results show the 5 year cumulative probability of developing complications was 41.5%, 15.6% for stricturing and 25.9% for penetrating complications.

In addition, perianal disease (hazard ratio [HR], 8.45; 95% confidence interval [CI], 4.74-15.07) and surgical resection of the intestine (HR, 2.71; 95% CI, 1.50-4.92) in the very early phase of disease was linked to a higher risk of developing a penetrating complication within the 5 year follow-up.

Using the bidirectional Montreal classification system, which accounts for disease regression, showed that 90% of patients exhibited inflammatory disease behavior at 5 years, compared to 58% if the hierarchical, unidirectional Montreal classification system was implemented.

“An additional bidirectional disease behavior assessment capturing reversed or fully controlled complications may provide a more realistic appraisal of the complexity and unmet needs of patients treated with advanced therapies,” the authors wrote.

References:

Bokemeyer, B., Plachta‐Danielzik, S., di Giuseppe, R., Helwig, U., Teich, N., Schmidt, C., Hartmann, P., Sobotzki, C., & Schreiber, S. (2023). Evaluation of a downstaging, bidirectional version of the Montreal classification of crohn's disease: Analysis of 5‐year follow‐up data from the prospective BioCrohn study. Alimentary Pharmacology & Therapeutics. https://doi.org/10.1111/apt.17512