OBJECTIVES: 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. We conducted a systematic review that focused on non-referral studies to reassess the role of 5-ASA for this indication.

METHODS: We 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.

RESULTS: Four observational studies fulfilled inclusion criteria. The pooled adjusted odds ratio (aOR) was 0.95 (95% confidence interval (CI): 0.66–1.38), but there was moderate heterogeneity (I²=58.2%;P=0.07). A sensitivity analysis that included a fifth study in which 5-ASA use was only for a minimum of 3 months yielded a pooled aOR of 0.82 (95% CI: 0.54–1.26). A series of sensitivity analyses in which each of the four studies was excluded one at a time did not show any significant change in the overall pooled OR. We conducted a separate meta-analysis of nine clinic-based studies, which, in contrast, yielded a pooled OR of 0.58 (95% CI: 0.45–0.75).

CONCLUSIONS: 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 CRC in IBD. However, heterogeneity among these studies limits their interpretation.