Introduction Thiopurines are the mainstay of treatment for patients with inflammatory bowel disease (IBD). Thiopurine therapy increases the risk of non-melanoma skin cancers (NMSC) in solid organ transplant patients. The data on NMSC in patients taking thiopurines for IBD is conflicting.
Methods We searched electronic databases (PubMed, OVID, the Cochrane library, EMBASE and CINAHL) for full journal articles reporting on the risk of developing NMSC in patients taking thiopurines for IBD and hand searched the reference lists of all retrieved articles. Pooled adjusted hazard ratios and 95% confidence intervals were determined using a random effects model. Publication bias was assessed using Funnel plots or Egger’s test for regression asymmetry. Heterogeneity was assessed using Cochran’s Q and the I2 statistic.
Results A total of 8 studies involving 60,351 patients provided data on the risk of developing NMSC in patients with IBD on thiopurines. The pooled adjusted hazard ratio of developing NMSC after exposure to thiopurines in patients with IBD was 2.275 (95% CI 1.502 to 3.446). There was significant heterogeneity (I2 76%) between the studies, but no evidence of publication bias (P = 0.15, intercept = –6.7 and 95% CI: –17.2 to 3.7). Meta regression analysis suggested that the population studied (hospital based versus population based) and duration of follow up (> 3 years) were the major contributors to the heterogeneity. Grouping studies according to population studied and also duration suggests that the risk was much higher in hospital based and shorter duration studies (Table).
Conclusion The risk of developing NMSC in patients with IBD on thiopurines is only modestly elevated. This effect loses significance when studies with less than 3 years follow-up are excluded. The difference in pooled risk between population based and hospital based studies suggests the possibility that ascertainment bias could have contributed to this increased risk. Use of thiopurines to treat IBD should not be limited by this marginally increased risk of NMSC.
Disclosure of Interest None Declared.
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