5-ASA and colorectal cancer chemoprevention in inflammatory bowel disease: can we afford to wait for 'best evidence'?

Patients with inflammatory bowel disease have a higher risk of developing colorectal cancer. The main risk factors for colorectal cancer are not suitable targets for therapeutic intervention, and primary chemoprevention is an intriguing therapeutic option. The analogies between acetyl-salicylic acid and 5-amino-salicylic acid, and the results obtained by using acetyl-salicylic acid as a chemopreventive agent in patients with sporadic colorectal cancer have prompted the study of potential chemopreventive effects of 5-amino-salicylic acid in inflammatory bowel disease. The results of both epidemiological and experimental studies have shown that long-term 5-amino-salicylic acid treatments appear to have a chemopreventive effect. The evidence for this effect is provided by retrospective and case-control studies whose results, however, do not reach the highest grades for evidence-based recommendations. Nevertheless, these results are supported by a series of experimental studies demonstrating the multiplicity of actions of 5-amino-salicylic acid. Although data regarding the chemopreventive effect of 5-amino-salicylic acid may not be rigorous enough to meet the criteria for the highest evidence-based medicine recommendations, we feel that the argument to wait until we have Grade A evidence is not necessarily rational in this case, because discontinuation of 5-amino-salicylic acid treatment to perform a randomised controlled trial would be unethical secondary to their proven efficacy for maintenance treatment.