Phenotypic features of Crohn's disease associated with failure of medical treatment

BACKGROUND & AIMS

There is conflicting evidence on the effects of thiopurines (azathioprine or mercaptopurine) and anti-tumor necrosis factor (TNF) therapies on rates of surgery among patients with Crohn's disease (CD). We aimed to identify factors that identify patients who are unlikely to respond to medical therapy and will therefore require surgery.

METHODS

We performed a retrospective study using the Alberta Inflammatory Bowel Disease Consortium registry to identify 425 patients diagnosed with CD who received a prescription of a thiopurine and/or an anti-TNF agent from a referral center, from July 1, 1975, through September 13, 2012. We collected data on CD-related abdominal surgery after therapy and disease features when therapy was instituted. Cox proportional regression models were used to associate disease features with outcomes after adjusting for potential confounders. Risk estimates were presented as hazard rate ratios (HRRs) with 95% confidence intervals (CIs).

RESULTS

Among patients given thiopurines, stricturing disease (adjusted HR, 4.63; 95% CI, 2.00-10.71), ileal location (adjusted HR, 6.20; 95% CI, 1.64-23.42), and ileocolonic location (adjusted HR, 3.71; 95% CI, 1.08-12.74) at the time of prescription were associated significantly with the need for surgery. Prescription of an anti-TNF agent after prescription of a thiopurine reduced the risk for surgery, compared with patients prescribed only a thiopurine (adjusted HR, 0.41; 95% CI, 0.22-0.75). Among patients given anti-TNF agents, stricturing (adjusted HR, 6.17; 95% CI, 2.81-13.54) and penetrating disease (adjusted HR, 3.39; 95% CI, 1.45-7.92) at the time of prescription were associated significantly with surgery. Older age at diagnosis (17-40 y) reduced the risk for abdominal surgery (adjusted HR, 0.41; 95% CI, 0.21-0.80) compared with a younger age group (≤16 y). Surgery before drug prescription reduced the risk for further surgeries among patients who received thiopurines (adjusted HR, 0.33; 95% CI, 0.13-0.68) or anti-TNF agents (adjusted HR, 0.49; 95% CI, 0.25-0.96). Terminal ileal disease location was not associated with a stricturing phenotype.

CONCLUSIONS

Based on a retrospective database analysis, patients prescribed thiopurine or anti-TNF therapy when they have a complicated stage of CD are more likely to require surgery. Better patient outcomes are achieved by treating CD at early inflammation stages; delayed treatment increases rates of treatment failure.

Drug-induced inflammatory bowel disease and IBD-like conditions

The pathogenesis of inflammatory bowel disease (IBD) is multifactorial and results from an interaction between genetic, immunologic, microbial, and environmental factors. Certain drugs could act as a trigger for the disease and have been implicated in the development of new onset IBD in a number a studies. These relationships are based on case reports and cohort studies, as proving this in the context of randomized controlled trials would be difficult. Drugs that have been linked to causing or worsening IBD include isotretinoin, antibiotics, nonsteroidal antiinflammatory drugs, oral contraceptives, mycophenolate mofetil, etanercept, ipilimumab, and rituximab. Bowel preparation for colonoscopy has also been associated with aphthoid lesions that may be confused with IBD. However, given the source of these reports we have to be cautious in the interpretation of the data before concluding that these drugs trigger IBD and what is being observed is not related to other confounding factors. Different pathogenic mechanisms have been suggested for the different drugs listed above. In order to clarify the confusion a comprehensive literature review was performed with the goal of advancing the knowledge on this subject.

Clinical predictors of thiopurine-related adverse events in Crohn's disease

AIM: To determine the incidence and predictors of thiopurine-related adverse events.

METHODS: Subjects with Crohn’s disease who were followed in the Alberta Inflammatory Bowel Disease Consortium patient database registry were identified. Retrospective chart review was conducted between August 5^th, 2010 and June 1^st, 2012. We collected data on: age at diagnosis; sex; disease location and behaviour at time of prescribing thiopurine; perianal fistulising disease at or prior to thiopurine prescription; smoking status at time of thiopurine prescription, use of corticosteroid within 6 mo of diagnosis; dosage, age at onset, and cessation of 5-aminosalicyclic acid (5-ASA); anti-tumour necrosis factor medication exposure and intestinal resection before thiopurine prescription. The primary outcome of interest was the first adverse event that led to discontinuation of the first thiopurine medication used. Logistic regression models were used to associate clinical characteristics with outcomes after adjusting for potential confounders. Risk estimates were presented as odds ratios (OR) with 95% CI. Effect modification by age and sex were explored.

RESULTS: Our cohort had a median follow-up duration of 5.8 years [interquartile range (IQR 25^th-75^th) 2.7-9.1]. Thiopurine therapy was discontinued in 31.3% of patients because of: hypersensitivity reactions (7.1%), acute pancreatitis (6.2%), gastrointestinal intolerance (5.4%), leucopenia (3.7%), hepatotoxicity (3.4%), infection (1.1%) and other reasons (4.3%). A higher incidence of thiopurine withdrawal was observed in patients over the age of 40 (39.4%, P = 0.007). A sex-by-age interaction (P = 0.04) was observed. Females older than 40 years of age had an increased risk of thiopurine discontinuation due to an adverse event (age above 40 vs age below 40, adjusted OR = 2.8; 95%CI: 1.4-5.6). In contrast, age did not influence thiopurine withdrawal in males (age above 40 vs below 40, adjusted OR = 0.9; 95%CI: 0.4-2.1). Other clinical variables (disease location and phenotype, perianal disease, smoking history, history of intestinal resection and prior 5-ASA or corticosteroid use) were not associated with an increased risk an adverse event leading to therapy cessation.

CONCLUSION: Thiopurine withdrawal due to adverse events is commoner in women over the age of 40 at prescription. These findings need to be replicated in other cohorts.

Novel concepts in inflammatory bowel disease

INTRODUCTION

Clinical management in inflammatory bowel disease (IBD) is constantly changing. Although improvement in symptoms is of paramount importance, using this as the only surrogate marker of disease activity might underestimate disease burden.

SOURCES OF DATA

New data from randomized clinical trials are now available. Treatment paradigms are constantly changing leading to an evolution in the therapeutic approach in routine IBD practice.

AREAS OF AGREEMENT

Patients with an aggressive disease phenotype should be identified at the onset and treated more intensely in order to achieve long-lasting mucosal remission.

AREAS OF CONTROVERSY

Patients who have mild and indolent disease need to be identified and not over treated.

GROWING POINTS

The primary endpoint in IBD management should ideally be mucosal healing. Ample data are now available that correlates mucosal healing with surgical-free outcomes with minimal intestinal damage and patient disability. However, the exact degree of mucosal healing that will lead to improved long-term remission, decreased hospital and surgical rates remains unknown.

AREAS TIMELY FOR DEVELOPING RESEARCH

Clinical translational work is needed to identify novel pathways in IBD pathogenesis that sub-select patients who would benefit by specific-cytokine pathway modulation.