PWE-359 Modifiable risk factors for serrated colorectal polyps: a systematic review and meta-analysis

Introduction Certain categories within the classification of serrated polyps (SP) of the colorectum are now understood to carry malignant potential. The serrated pathway accounts for at least 15% of all colorectal cancers. The aim of this systematic review was to investigate the association between modifiable lifestyle factors and risk of SP. Method A search was conducted systematically within three databases, Medline, Embase and Web of Science, for relevant literature published by October 2014. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were combined using random effects meta-analyses to assess the risk of SP, where possible. Results Thirty-six papers were identified for inclusion in the review, analysing SP risk and seven different lifestyle factors: smoking, alcohol, body fatness, diet, physical activity, non-steroidal anti-inflammatory drug (NSAID) use and/or infectious agents. When comparing the highest and lowest categories of exposure, significant elevated risks of SP were identified for tobacco smoking (OR 2.78, 95% CI 2.30-3.34); alcohol intake (OR 1.36, 95% CI 1.19-1.56), and body mass index (OR 1.46, 95% CI 1.19-1.79). Contrastingly, significant decreased SP risks were observed for NSAID (OR 0.77, 95% CI 0.63-0.94) and aspirin users (OR 0.77, 95% CI 0.65-0.92), compared with non-users. No significant associations were detected for SP risk and physical activity, while associations with dietary factors were mixed. Most studies had not separately identified sessile serrated adenomas/polyps from hyperplastic polyps in their analyses, as publication predated widespread recognition of this novel serrated polyp category. Conclusion This systematic review has identified novel associations for several lifestyle factors and risk of SP, subgroups of which have recently been implicated in carcinogenesis. These findings enhance our understanding of potential mechanisms involved, and suggest that SP (and ultimately colorectal cancer) risk could be reduced via changes in lifestyle. Further studies are needed to report on specific SP categories. Disclosure of interest None Declared.