Systematic review with meta‐analysis: thiopurines decrease the risk of colorectal neoplasia in patients with inflammatory bowel disease

Summary Background Patients with inflammatory bowel disease ( IBD ) have a high risk of developing colorectal neoplasia. Aim To investigate whether thiopurines can decrease the risk of developing colorectal neoplasia in patients with ulcerative colitis ( UC ) or Crohn's disease ( CD ). Methods We conducted a meta‐analysis of 24 observational studies involving 76,999 participants to evaluate the risks of developing colorectal neoplasia in IBD patients receiving thiopurine treatment. Pooled odds ratios ( OR s) and 95% confidence intervals ( CI s) for the risks of colorectal neoplasia were calculated using a random‐effects model. Results The overall pooled estimate revealed a protective effect of thiopurine use on colorectal neoplasia in patients with IBD ( OR  = 0.63, 95% CI 0.46‐0.86). The effect was significant in UC patients ( OR  = 0.67, 95% CI 0.45‐0.98), but was not significant in CD patients ( OR  = 1.06, 95% CI 0.54‐2.09). Thiopurines exposure significantly decreased the risk of colorectal cancer ( CRC ) ( OR  = 0.65, 95% CI 0.45‐0.96) and advanced colorectal neoplasia ( CRC and/or high‐grade dysplasia) ( OR  = 0.62, 95% CI 0.44‐0.89), but did not decrease the risk of dysplasia alone ( OR  = 0.90, 95% CI 0.37‐2.21). Tendencies towards the protective effect of thiopurines were distinct in clinic‐based studies ( OR  = 0.59, 95% CI 0.42‐0.82) and case‐control studies ( OR  = 0.40, 95% CI 0.26‐0.62), but not in population‐based studies ( OR  = 0.95, 95% CI 0.55‐1.62) and cohort studies ( OR  = 0.98, 95% CI 0.81‐1.18). Interestingly, studies conducted in Europe ( OR  = 0.48, 95% CI 0.31‐0.77), rather than in North America ( OR  = 0.91, 95% CI 0.67‐1.24), showed the protective effect of thiopurines. Conclusions This meta‐analysis revealed an antineoplastic effect of thiopurines on colorectal neoplasia in patients with IBD , particularly amongst patients with UC .