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Some studies have demonstrated that 5-aminosalicylic acid (5-ASA) is associated with a reduced risk of colorectal cancer (CRC) in inflammatory bowel disease (IBD). However, more recent population-based studies suggest no protective association. Dr Geoffrey Nguyen and colleagues from Canada conducted a systematic review that focused on non-referral studies to reassess the role of 5-ASA for this indication. The team searched MEDLINE, EMBASE, and the Cochrane databases for studies of non-referral populations that assessed the association between 5-ASA use for at least 1 year, and colorectal neoplasia between 1966 and 2011, and conducted a quantitative meta-analysis. The team identified 4 observational studies that fulfilled inclusion criteria.  | | The sensitivity analysis yielded a pooled adjusted odds ratio of 0.8 | | American Journal of Gastroenterology |
The pooled adjusted odds ratio was 0.95, but there was moderate heterogeneity. The research team performed a sensitivity analysis that included a fifth study in which 5-ASA use was only for a minimum of 3 months. The sensitivity analysis yielded a pooled adjusted odds ratio of 0.8. A series of sensitivity analyses in which each of the 4 studies was excluded one at a time did not show any significant change in the overall pooled odds ratio. The research team conducted a separate meta-analysis of 9 clinic-based studies, which, in contrast, yielded a pooled odds ratio of 0.6. Dr Nguyen's team concludes, "Our meta-analysis yielded inconsistent results that were dependent on the inclusion of either non-referral or clinic-based populations." "Based on non-referral studies, there does not seem to be a protective effect of 5-ASA on colorectal cancer in IBD." "However, heterogeneity among these studies limits their interpretation."
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