Mucosal improvement in patients with moderate to severe postoperative endoscopic recurrence of Crohn's disease and azathioprine metabolite levels

Results of the Eighth Scientific Workshop of ECCO: Prevention and Treatment of Postoperative Recurrence in Patients With Crohn's Disease Undergoing an Ileocolonic Resection With Ileocolonic Anastomosis

Despite the introduction of biological therapies, an ileocolonic resection is often required in patients with Crohn's disease [CD]. Unfortunately, surgery is not curative, as many patients will develop postoperative recurrence [POR], eventually leading to further bowel damage and a decreased quality of life. The 8th Scientific Workshop of ECCO reviewed the available scientific data on both prevention and treatment of POR in patients with CD undergoing an ileocolonic resection, dealing with conventional and biological therapies, as well as non-medical interventions, including endoscopic and surgical approaches in case of POR. Based on the available data, an algorithm for the postoperative management in daily clinical practice was developed.

Normal Ranges of Thiopurine Methyltransferase Activity Do Not Affect Thioguanine Nucleotide Concentrations With Azathioprine Therapy in Inflammatory Bowel Disease

Background

Thiopurine methyltransferase (TPMT) activity influences azathioprine conversion into active metabolite 6-thioguanine nucleotide (6-TGN). Low TPMT activity correlates with high 6-TGN and risk for myelosuppression. Conversely, normal-to-high TPMT activity may be associated with low 6-TGN and drug resistance, the so-called hypermetabolizers. Our aim was to identify the effect of normal-to-high TPMT activity on 6-TGN concentrations in an inflammatory bowel disease population.

Methods

A retrospective chart review of patients aged ≥18 with inflammatory bowel disease, on azathioprine, with documented TPMT activity and 6-TGN concentration was performed. Correlations were evaluated via the Spearman rho correlation coefficient. Linear regression was used to determine the effect of TPMT activity on 6-TGN accounting for confounders. Relationships between TPMT activity, drug dose, and 6-TGN levels were defined via average causal mediation effects.

Results

One hundred patients were included. No correlation was observed between TPMT activity, azathioprine dosing, and metabolite concentrations. Overall, 39% of the cohort had a therapeutic 6-TGN level of >230 pmol/8 × 10⁸ red blood cells (RBCs). No patient under 1 mg/kg achieved a therapeutic 6-TGN level, whereas 42% of patients taking 2.5 mg/kg did. The median 6-TGN concentration was higher for those in remission (254 pmol/8 × 10⁸ RBCs, interquartile range: 174, 309) versus those not in remission (177 pmol/8 × 10⁸ RBCs, interquartile range: 94.3, 287.8), though not significantly (P = 0.08). Smoking was the only clinical factor associated with 6-TGN level. On multivariate linear regression, only age, azathioprine dose, and obese body mass index were predictive of metabolite concentration.

Conclusions

Variations within the normal range of TPMT activity do not affect 6-TGN concentration.

Interventions for maintenance of surgically induced remission in Crohn's disease: a network meta-analysis

BACKGROUND

Crohn's disease (CD) is a chronic disease of the gut. About 75% of people with CD undergo surgery at least once in their lifetime to induce remission. However, as there is no known cure for the disease, patients usually experience a recurrence even after surgery. Different interventions are routinely used in maintaining postsurgical remission. There is currently no consensus on which treatment is the most effective.

OBJECTIVES

To assess the effects and harms of interventions for the maintenance of surgically induced remission in Crohn's disease and rank the treatments in order of effectiveness.

SEARCH METHODS

We searched the Cochrane IBD Group Specialized Register, CENTRAL, MEDLINE, and Embase from inception to 15 January 2019. We also searched reference lists of relevant articles, abstracts from major gastroenterology meetings, ClinicalTrials.gov, and the WHO ICTRP. There was no restriction on language, date, or publication status.

SELECTION CRITERIA

We considered for inclusion randomised controlled trials (RCTs) that compared different interventions used for maintaining surgically induced remission in people with CD who were in postsurgical remission. Participants had to have received maintenance treatment for at least three months. We excluded studies assessing enteral diet, diet manipulation, herbal medicine, and nutritional supplementation.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected relevant studies, extracted data, and assessed the risk of bias. Any disagreements were resolved by discussion or by arbitration of a third review author when necessary. We conducted a network meta-analysis (NMA) using a Bayesian approach through Markov Chain Monte Carlo (MCMC) simulation. For the pairwise comparisons carried out in Review Manager 5, we calculated risk ratios (RR) with their corresponding 95% confidence intervals (95% CI). For the NMA, we presented hazard ratios (HR) with corresponding 95% credible intervals (95% CrI) and reported ranking probabilities for each intervention. For the NMA, we focused on three main outcomes: clinical relapse, endoscopic relapse, and withdrawals due to adverse events. Data were insufficient to assess time to relapse and histologic relapse. Adverse events and serious adverse events were not sufficiently or objectively reported to permit an NMA. We used CINeMA (Confidence in Network Meta-Analysis) methods to evaluate our confidence in the findings within networks, and GRADE for entire networks.

MAIN RESULTS

We included 35 RCTs (3249 participants) in the review. The average age of study participants ranged between 33.6 and 38.8 years. Risk of bias was high in 18 studies, low in four studies, and unclear in 13 studies. Of the 35 included RCTs, 26 studies (2581 participants; 9 interventions) were considered eligible for inclusion in the NMA. The interventions studied included 5-aminosalicylic acid (5-ASA), adalimumab, antibiotics, budesonide, infliximab, probiotics, purine analogues, sulfasalazine, and a combination of sulfasalazine and prednisolone. This resulted in 30 direct contrasts, which informed 102 mixed-treatment contrasts.The evidence for the clinical relapse network (21 studies; 2245 participants) and endoscopic relapse (12 studies; 1128 participants) were of low certainty while the evidence for withdrawal due to adverse events (15 studies; 1498 participants) was of very low certainty. This assessment was due to high risk of bias in most of the studies, inconsistency, and imprecision across networks. We mainly judged individual contrasts as of low or very low certainty, except 5-ASA versus placebo, the evidence for which was judged as of moderate certainty.We ranked the treatments based on effectiveness and the certainty of the evidence. For clinical relapse, the five most highly ranked treatments were adalimumab, infliximab, budesonide, 5-ASA, and purine analogues. We found some evidence that adalimumab (HR 0.11, 95% Crl 0.02 to 0.33; low-certainty evidence) and 5-ASA may reduce the probability of clinical relapse compared to placebo (HR 0.69, 95% Crl 0.53 to 0.87; moderate-certainty evidence). However, budesonide may not be effective in preventing clinical relapse (HR 0.66, 95% CrI 0.27 to 1.34; low-certainty evidence). We are less confident about the effectiveness of infliximab (HR 0.36, 95% CrI 0.02 to 1.74; very low-certainty evidence) and purine analogues (HR 0.75, 95% CrI 0.55 to 1.00; low-certainty evidence). It was unclear whether the other interventions reduced the probability of a clinical relapse, as the certainty of the evidence was very low.Due to high risk of bias and limited data across the network, we are uncertain about the effectiveness of interventions for preventing endoscopic relapse. Whilst there might be some evidence of prevention of endoscopic relapse with adalimumab (HR 0.10, 95% CrI 0.01 to 0.32; low-certainty evidence), no other intervention studied appeared to be effective.Due to high risk of bias and limited data across the network, we are uncertain about the effectiveness of interventions for preventing withdrawal due to adverse events. Withdrawal due to adverse events appeared to be least likely with sulfasalazine (HR 1.96, 95% Crl 0.00 to 8.90; very low-certainty evidence) and most likely with antibiotics (HR 53.92, 95% Crl 0.43 to 259.80; very low-certainty evidence). When considering the network as a whole, two adverse events leading to study withdrawal (i.e. pancreatitis and leukopenia) occurred in more than 1% of participants treated with an intervention. Pancreatitis occurred in 2.8% (11/399) of purine analogue participants compared to 0.17% (2/1210) of all other groups studied. Leukopenia occurred in 2.5% (10/399) of purine analogue participants compared to 0.08% (1/1210) of all other groups studied.

AUTHORS' CONCLUSIONS

Due to low-certainty evidence in the networks, we are unable to draw conclusions on which treatment is most effective for preventing clinical relapse and endoscopic relapse. Evidence on the safety of the interventions was inconclusive, however cases of pancreatitis and leukopenia from purine analogues were evident in the studies. Larger trials are needed to further understand the effect of the interventions on endoscopic relapse.

Azathioprine and 6-mercaptopurine for maintenance of surgically-induced remission in Crohn's disease

BACKGROUND

Crohn's disease (CD) is a chronic relapsing inflammatory condition and maintenance of remission is a major issue as many patients fail to achieve remission with medical management and require surgical interventions. Purine analogues such as azathioprine (AZA) and 6-mercaptopurine (6-MP) have been used to maintain surgically-induced remission in CD, but the effectiveness, tolerability and safety of these agents remains controversial.

OBJECTIVES

To assess the efficacy and safety of purine analogues (AZA and 6-MP) for maintenance of surgically-induced remission in CD.

SEARCH METHODS

We searched PubMed, MEDLINE, Embase, CENTRAL, and the Cochrane IBD Group Specialized Register from inception to 26 July 2018 (and from inception to 31 July 2019). In addition, we searched reference lists of all included studies and relevant reviews, conference proceedings and trials registers.

SELECTION CRITERIA

Randomised controlled trials (RCTs) with a duration of at least three months that enrolled adults and children with surgically-induced remission of CD and compared AZA or 6-MP to no treatment, placebo or any other active intervention were considered for inclusion.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial eligibility, extracted data, assessed the risk of bias and assessed the certainty of the evidence using GRADE. The primary outcome was clinical relapse. Secondary outcomes included endoscopic relapse, radiologic and surgical relapse, adverse events (AEs), serious adverse events (SAEs), withdrawal due to AEs and health-related quality of life.

MAIN RESULTS

Ten RCTs with a total of 928 participants were included. Study participants were adults recruited from university clinics and gastroenterology hospitals who received interventions post-surgery for a duration between 12 to 36 months. Most study participants were recruited less than three months after surgery in all except one study where participants were recruited between 6 to 24 months post-surgery. One study was rated as low risk of bias, six studies were rated high risk of bias and three were rated unclear risk of bias.There was moderate certainty evidence that purine analogues are more efficient for preventing clinical relapse than placebo. At 12 to 36 months, 51% (109/215) of AZA/6-MP participants relapsed compared to 64% (124/193) of placebo participants (RR 0.79; 95% CI 0.67 to 0.92; 408 participants; 3 studies; I² = 0%; moderate certainty evidence). The certainty of the evidence regarding the efficacy of AZA or 6-MP for maintaining postoperative clinical remission compared to 5-ASA compounds was low. At 12 to 24 months , 64% (113/177) of purine analogue participants relapsed compared to 59% (101/170) of 5-ASA participants (RR 1.05; 95% CI 0.89 to 1.24; 347 participants; 4 studies; I² = 8%; low certainty evidence). The certainty of evidence that purine analogues are inferior for preventing postsurgical clinical relapse compared to tumour necrosis factor alpha agents (anti-TNF-α) was very low. At 12 to 24 months, 43% (29/67) of AZA participants relapsed compared to 14% (10/72) of anti-TNF-α participants (RR 2.89; 95% CI 1.50 to 5.57; 139 participants; 3 studies; I² = 0%; very low certainty evidence).The effect of purine analogues compounds on AEs compared to placebo or any active treatment was uncertain, as the quality of evidence ranged from very low to low. After 12 to 24 months, 14% (12/87) of purine analogue participants experienced an AE compared to 10% (8/81) of placebo participants (RR 1.36; 95% CI 0.57 to 3.27; 168 participants; 2 studies; I² = 0%; low certainty evidence). The effect of purine analogues on AEs compared to 5-ASA agents was uncertain. After 12 to 24 months, 41% (73/176) of purine analogue participants had an AE compared to 47% (81/171) of 5-ASA participants (RR 0.89; 95% CI 0.74 to 1.07; 346 participants; 4 studies; I² = 15%; low certainty evidence). The effect of purine analogues on AEs in comparison to anti TNF-α agents was uncertain. At 12 to 24 months, 57% (32/56) of AZA participants had an AE compared to 51% (31/61) of anti-TNF-α participants (RR 1.13; 95% CI 0.83 to 1.53; 117 participants; 2 studies; I² = 0%; low certainty evidence). Purine analogue participants were more like than 5-ASA participants to have a SAE (RR 3.39, 95% CI 1.26 to 9.13, 311 participants; 3 studies; I² = 9%; very low certainty evidence), or to withdraw due to an AE (RR 2.21, 95% CI 1.28 to 3.81; 425 participants; 5 studies; I² = 0%; low certainty evidence). Commonly reported AEs across all studies included leucopenia, arthralgia, abdominal pain or severe epigastric intolerance, elevated liver enzymes, nausea and vomiting, pancreatitis, anaemia, nasopharyngitis and flatulence.

AUTHORS' CONCLUSIONS

Moderate certainty evidence suggests that AZA and 6-MP may be superior to placebo for maintenance of surgically-induced remission in participants with CD. There was no clear difference in the number of clinical relapses when purine analogues were compared with 5-ASA agents, however this is based on low certainty evidence. There was very low certainty evidence that AZA and 6-MP are more likely to result in more serious adverse events (SAEs) and withdrawals due to an AE (low certainty) when compared to 5-ASA agents. Very low certainty evidence suggests that purine analogues may be inferior to anti-TNF-α agents, however, no firm conclusions can be drawn. Further research investigating the efficacy and safety of AZA and 6-MP in comparison to other active medications in surgically-induced remission of CD is warranted.

Fecal calprotectin is significantly linked to azathioprine metabolite concentrations in Crohn's disease

BACKGROUND

The value of therapeutic drug monitoring during azathioprine (AZA) therapy with respect to clinical outcomes has been convincingly demonstrated in recent meta-analyses. However, the association between AZA metabolites and the mucosal state in inflammatory bowel disease is largely unclear.

AIMS

We investigated the association between AZA's active metabolite 6-thioguanine nucleotides (6-TGN) and fecal calprotectin (FC) as a well-validated surrogate marker of mucosal inflammation in patients with Crohn's disease (CD) on AZA monotherapy.

PATIENTS AND METHODS

Of 443 6-TGN measurements, 140 values from 88 patients with CD on AZA monotherapy visiting the inflammatory bowel disease outpatient clinic between 2009 and 2016 were retrospectively analyzed. In a subcohort with serial 6-TGN measurements, longitudinal FC measurements in patients with versus without intervention (dose increase, allopurinol, and education) were assessed.

RESULTS

In patients with 6-TGN concentrations within a predefined range (250-450 pmol/8×10 red blood cells), FC was significantly lower (median: 119.5 vs. 327.2 mg/kg, P=0.003), and hemoglobin as well as serum protein concentrations were significantly higher than in patients with 6-TGN outside of this range. C-reactive protein and transferrin saturation were not different. In the longitudinal cohort, 6-TGN increased in the intervention group, but only a minority reached the defined range; no significant change in FC was observed.

CONCLUSION

This study is the first to show that in patients with CD receiving AZA monotherapy, 6-TGN concentrations within a defined range (250-450 pmol/8×10 red blood cells) are associated with significantly lower FC. A treat-to-target concept directed by 6-TGN to reach mucosal healing may thus be a promising approach (DRKS00013246).

6-Thioguanine Nucleotide Levels Are Associated With Mucosal Healing in Patients With Crohn's Disease

BACKGROUND

Level of 6-thioguanine nucleotides (6-TGN) has been reported to be associated with clinical remission in patients with Crohn's disease (CD) receiving maintenance treatment with thiopurines. Whether 6-TGN levels are associated with mucosal healing (MH) has seldom been investigated. We aimed to assess the correlation between 6-TGN levels and MH in patients with CD.

METHODS

This was a retrospective, cross-sectional, observational, multicenter study of 119 patients with CD treated with thiopurines in 3 inflammatory bowel disease referral centers (France, Australia, and China) between June 2012 and April 2016. Established CD patients who underwent ileocolonoscopy during thiopurine treatment were included. MH was defined as simple endoscopic score-CD <3. Univariate and multivariable regression analyses were used to evaluate variables associated with MH.

RESULTS

The mean concentration of 6-TGN in the MH group was higher compared with that in the non-MH group (359.0 ± 226.7 pmol/8 × 108 red blood cell count [RBC] vs 277.1 ± 170.5 pmol/8 × 108 RBC; P = 0.017). The cutoff 6-TGN concentration of 397.3 pmol/8 × 108 RBC was 86.7% specific to MH, with a sensitivity of 35.3% and area under curve (AUC) of 0.631 (P = 0.010). On multivariable analysis, 6-TGN levels were associated with MH (odds ratio [OR], 3.287; 95% confidence interval [CI], 1.348-8.017; P = 0.009) whereas late initiation of AZA (longer duration from disease onset) was inversely associated with MH (OR, 0.972; 95% CI, 0.954-0.991; P = 0.004).

CONCLUSIONS

Higher 6-TGN levels are independently associated with a reduced rate of endoscopically active disease and a higher rate of mucosal healing in CD patients. Prospective studies of adequate sample size are required to confirm these findings.

NASPGHAN Clinical Report on Postoperative Recurrence in Pediatric Crohn Disease

Pediatric Crohn disease is characterized by clinical and endoscopic relapses. The inflammatory process is considered to be progressive and may lead to strictures, fistulas, and penetrating disease that may require surgery. In addition, medically refractory disease may be treated by surgical resection of inflamed bowel in an effort to reverse growth failure. The need for surgery in childhood suggests severe disease and these patients have an increased risk for recurrent disease and potentially more surgery. Data show that up to 55% of patients had clinical recurrence in the first 2 years after initial surgery. The current clinical report on postoperative recurrence in pediatric Crohn disease reviews the risk factors for early surgery and postoperative recurrence, operative risk factors for recurrence, and prevention and monitoring strategies for postoperative recurrence. We also propose an algorithm for postoperative management in pediatric Crohn disease.

Thiopurines and inflammatory bowel disease: Current evidence and a historical perspective

The use of thiopurines in inflammatory bowel disease (IBD) has been examined in numerous prospective, controlled trials, with a majority demonstrating a clinical benefit. We conducted this review to describe the historical and current evidence in the use of thiopurines in IBD. A systematic search was performed on MEDLINE between 1965 and 2016 to identify studies on thiopurines in IBD. The most robust evidence for thiopurines in IBD includes induction of remission in combination with anti-tumor necrosis factor (anti-TNF) agents, and maintenance of remission and post-operative maintenance in Crohn’s disease. Less evidence exists for thiopurine monotherapy in induction of remission, maintenance of ulcerative colitis, chemoprevention of colorectal cancer, and in preventing immunogenicity to anti-TNF. Evidence was often limited by trial design. Overall, thiopurines have demonstrated efficacy in a broad range of presentations of IBD. With more efficacious novel therapeutic agents, the positioning of thiopurines in the management of IBD will change and future studies will analyze the benefit of thiopurines alone and in conjunction with these new medications.

Monitoring thiopurine metabolites in inflammatory bowel disease

Thiopurines (azathioprine and mercaptopurine) are one of the immunosuppressive mainstays for the treatment of inflammatory bowel disease. In spite of its widespread use, thiopurine metabolism is still not fully understood, and a significant proportion of patients suffer toxicity or lack of efficacy. Different enzymatic pathways with individual variations constitute a pharmacogenetic model that seems to be suitable for monitoring and therapeutic intervention. This review is focused on current concepts and recent research that may help clinicians to rationally optimise thiopurine treatment in patients with inflammatory bowel disease.

Optimal delivery of follow-up care after surgery for Crohn's disease: current perspectives

Despite improvements in medical therapies for Crohn’s disease (CD), up to 70% of patients require surgery within 10 years of diagnosis. Surgery is not curative, and almost all patients will experience endoscopic recurrence, and many will go on to clinical recurrence. Identifying patients at high-risk of endoscopic recurrence and standardizing postoperative assessments are essential in preventing clinical recurrence of CD. In this review, we discuss the assessment, monitoring, and treatment of postoperative CD patients. We address the various individual risk factors as well as composite risk factors. Medications used for primary CD treatment can be used in the postoperative setting to prevent endoscopic or clinical recurrence with varying efficacy, although the cost-effectiveness of these approaches are not fully understood. Future directions for postoperative CD management include evaluation of newer biologic agents such as anti-integrin therapy and fecal microbiota transplant for prevention of recurrence. Development of a standard preoperative risk assessment tool to clearly stratify those at high-risk of recurrence is necessary to guide empiric therapy. Lastly, the incorporation of noninvasive testing into disease monitoring will likely lead to early detection of endoscopic recurrence that will allow for tailored treatment to prevent clinical recurrence.

Systematic review with meta-analysis: mucosal healing is associated with improved long-term outcomes in Crohn's disease

BACKGROUND

Clinical manifestations of Crohn's disease (CD) do not reliably correlate with endoscopic activity. While treating to achieve clinical remission (CR) has neither proven to improve CD outcomes nor alter the natural disease course, it is unclear whether targeting objective measures like mucosal healing (MH) is associated with improved long-term outcomes.

AIM

To perform a systematic review and meta-analysis comparing long-term outcomes in active CD patients who achieve MH compared to those who do not.

METHODS

We performed a systematic literature search to identify studies with prospective cohorts of active CD patients that included outcomes of patients who achieved MH at first endoscopic assessment (MH1) compared to those who did not. The primary outcome was long-term (≥50 weeks) CR. Secondary outcomes included CD-related surgery-free rate, hospitalisation-free rate and long-term MH rate. Pooled odds ratio (OR) and 95% confidence intervals (CI) were calculated.

RESULTS

Twelve studies with 673 patients met inclusion criteria. Patients achieving MH1 had a pooled OR of 2.80 (95%CI, 1.91-4.10) for achieving long-term CR, 2.22 (95%CI, 0.86-5.69) for CD-related surgery-free rate, and 14.30 (95%CI, 5.57-36.74) for long-term MH. Sensitivity analyses suggested no difference in outcomes if MH1 was achieved on biologics vs. non-biologics. No significant publication bias or heterogeneity was detected.

CONCLUSIONS

Achieving MH1 is associated with increased rates of long-term clinical remission, and maintenance of mucosal healing in active Crohn's disease and may therefore be a reasonable therapeutic target.

Azathioprine and 6-mercaptopurine for maintenance of surgically-induced remission in Crohn's disease

BACKGROUND

Crohn's disease (CD) is a chronic relapsing inflammatory condition. Many patients fail to achieve remission with medical management and require surgical interventions. Purine analogues have been used to maintain surgically-induced remission in CD, but the effectiveness of these agents is unclear.

OBJECTIVES

The objectives were to evaluate the efficacy and safety of purine analogues for maintenance of surgically-induced remission in CD.

SEARCH METHODS

We searched the following databases from inception to 30 April 2014: PubMed, MEDLINE, EMBASE, CENTRAL, and the Cochrane Inflammatory Bowel Disease and Functional Bowel Disorders Group Specialized Trials Register). We also searched the reference lists of all included studies, and contacted personal sources and drug companies to identify additional studies. The searches were not limited by language.

SELECTION CRITERIA

Randomised controlled trials (RCTs) that compared purine analogues to placebo or another intervention, with treatment durations of at least six months were considered for inclusion. Participants were patients of any age with CD in remission following surgery.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial eligibility and extracted data. Methodological quality was assessed using the Cochrane risk of bias tool. The primary outcome measures were clinical and endoscopic relapse as defined by the primary studies. Secondary outcomes included adverse events, withdrawal due to adverse events and serious adverse events. Data were analysed on an intention-to-treat basis where patients with missing final outcomes were assumed to have relapsed. We calculated the risk ratio (RR) and corresponding 95% confidence interval (95% CI) for dichotomous outcomes. The Chi(2) and I(2) statistics were used to assess heterogeneity. The overall quality of the evidence supporting the primary outcomes and selected secondary outcomes was assessed using the GRADE criteria.

MAIN RESULTS

Seven RCTs (n = 584 patients) were included in the review. Three studies compared azathioprine to 5-aminosalicylic acid (5-ASA). One small study compared azathioprine to both 5-ASA and adalimumab. One study compared azathioprine to placebo and another study compared 6-mercaptopurine to 5-ASA and placebo. One small study compared azathioprine to infliximab. Three studies were judged to be at low risk of bias. Four studies were judged to be at high risk of bias due to blinding. The study (n = 22) comparing azathioprine to infliximab found that the effects on the proportion of patients who had a clinical (RR 2.00, 95% CI 0.21 to 18.98) or endoscopic relapse (RR 4.40, 95% CI 0.59 to 3.07) were uncertain. One study (n = 33) found decreased clinical (RR 5.18, 95% CI 1.35 to 19.83) and endoscopic relapse (RR 10.35, 95% CI 1.50 to 71.32) rates favouring adalimumab over azathioprine. A pooled analysis of two studies (n = 168 patients) showed decreased clinical relapse rates at one or two years favouring purine analogues over placebo. Forty-eight per cent of patients in the purine analogue group experienced a clinical relapse compared to 63% of placebo patients (RR 0.74, 95% CI 0.58 to 0.94). A GRADE analysis indicated that the overall quality of the evidence supporting this outcome was low due to high risk of bias (one study was single-blind) and sparse data (93 events). One study (87 patients) found a reduction in endoscopic relapse rates favouring 6-mercaptopurine over placebo. Seventeen per cent of 6-mercaptopurine patients had an endoscopic relapse at two years compared to 42% of placebo patients (RR 0.40, 95% CI 0.19 to 0.83). A GRADE analysis indicated that the overall quality of the evidence for this outcome was low due to very sparse data (25 events). A pooled analysis of five studies (n = 425 patients) showed no difference in clinical relapse rates at one or two years between purine analogues and 5-ASA agents. Sixty-three per cent of patients in the purine analogues group experienced a clinical relapse compared to 54% of 5-ASA patients (RR 1.15, 95% CI 0.99 to 1.34). A GRADE analysis indicated that the overall quality of the evidence supporting this outcome was very low due to high risk of bias (two open-label studies), sparse data (249 events) and moderate heterogeneity (I(2) = 45%). There was no difference in endoscopic relapse at 12 months between azathioprine and 5-ASA (RR 0.78, 95% CI 0.52 to 1.17; 1 study, 35 patients). A GRADE analysis indicated that the overall quality of the evidence for this outcome was very low due to high risk of bias (open-label study) and very sparse data (26 events). There was a reduction in endoscopic relapse at 24 months favouring 6-mercaptopurine over 5-ASA patients. Seventeen per cent of 6-mercaptopurine patients had an endoscopic relapse compared to 48% of 5-ASA patients (RR 0.36, 95% CI 0.18 to 0.72; 1 study, 91 patients). A GRADE analysis indicated that the overall quality of the evidence for this outcome was low due to very sparse data (29 events). Adverse events that required withdrawal were more common in the purine analogue group compared to 5-ASA. Twenty per cent of patients in the purine analogue group withdrew due to adverse events compared to 10% of 5-ASA patients (RR 2.07, 95% CI 1.26 to 3.39; 5 studies, 423 patients).The results for withdrawal due to adverse events between purine analogues and placebo or for other comparisons were uncertain. Commonly reported adverse events across all studies included leucopenia, arthralgia, abdominal pain or severe epigastric intolerance, elevated liver enzymes, nausea and vomiting, pancreatitis, anaemia, exacerbation of Crohn's disease, nasopharyngitis, and flatulence.

AUTHORS' CONCLUSIONS

Purine analogues may be superior to placebo for maintenance of surgically-induced remission in patients with CD, although this is based on two small studies. The results for efficacy outcomes between purine analogues and 5-ASA agents were uncertain. However, patients taking purine analogues were more likely than 5-ASA patients to discontinue therapy due to adverse events. No firm conclusions can be drawn from the two small studies that compared azathioprine to infliximab or adalimumab. Adalimumab may be superior to azathioprine but further research is needed to confirm these results. Further research investigating the efficacy and safety of azathioprine and 6-mercaptopurine in comparison to other active medications in patients with surgically-induced remission of CD is warranted.

The role of thiopurine metabolite monitoring in inflammatory bowel disease

Thiopurines are the mainstay of medical management in inflammatory bowel disease (IBD), especially in the maintenance of disease remission. Given the limited IBD armamentarium it is important to optimize each therapy before switching to an alternative drug. Conventional weight based dosing of thiopurines in IBD leads to intolerance or inefficacy in many patients. More recently increased knowledge of their metabolism has allowed for dose optimization using thiopurine metabolite levels, namely 6-thioguanine nucleotides and 6-methylmercaptopurine, with the potential for improved outcomes in patients with IBD. This review will outline the current understanding of thiopurine metabolism and pharmacogenomics and will describe the clinical application of this knowledge in the optimization of thiopurines in individual patients.

Positioning therapy for Crohn's disease

The therapy of Crohn's disease is constantly evolving. It is widely recognized that clinical assessment does not stage disease activity accurately and that endoscopic healing is associated with improved long-term outcomes. Disease management is therefore transitioning to a new paradigm that includes direct assessment of disease severity (endoscopically in most patients), followed by assessment of mucosal healing. New approaches have helped optimize the use of the thiopurines, methotrexate and anti-TNF agents. Novel agents with different mechanisms of action are expanding our therapeutic armamentarium. The major challenge of the future will be to identify patient subgroups best suited to particular therapeutic approaches. In the meantime, studies of comparative effectiveness will be crucial in positioning therapies relative to each other.