Nonalcoholic Fatty Liver Disease and Risk of Colorectal Tumours: A Meta-Analysis

Background and Aims: it remains currently uncertain if nonalcoholic fatty liver disease (NAFLD) is associated with an increased risk of colorectal tumours. We performed a meta-analysis of relevant studies to quantify the magnitude of the association between NAFLD and risk of colorectal tumours. Methods: we searched PubMed, Scopus and Web of Science (up to November 15, 2017) using pre-defined key-words to identify observational cohort studies of asymptomatic adult individuals undergoing screening colonoscopy, in which NAFLD was diagnosed by liver biopsy or imaging methods (mainly ultrasonography). Data from selected studies were extracted, and meta-analysed using random-effects modelling. Results: eleven observational cohort studies (8 cross-sectional and 3 longitudinal) with aggregate data on 91124 adult individuals of predominantly Asian descent (32.1% with NAFLD) and a total of 14641 colorectal adenomas and 1627 cancers were included in the final analysis. NAFLD was associated with an increased risk of both prevalent colorectal tumours (n=8 studies; random-effects odds ratio 1.40, 95%CI 1.2-1.6. I2=78.8%) and incident colorectal tumours (n=3 studies with a median follow-up of 5 years; random-effects hazard ratio 1.47, 95%CI 1.2-1.8. I2=11.5%). These risks were independent of multiple common risk factors, such as age, sex, BMI, smoking, diabetes or metabolic syndrome. The presence of more severe NAFLD (n=3 studies) was associated with a nearly two-fold increased risk of adenomas and with a nearly 2.5-fold increased risk of cancer. Sensitivity analyses did not alter these findings. Funnel plot and Egger’s test did not reveal significant publication bias. Conclusions: this largest and most updated meta-analysis to date shows that NAFLD is associated with a 40% increased risk of prevalent colorectal tumours and with a nearly 50% increased long-term risk of incident colorectal tumours in asymptomatic adult individuals undergoing screening colonoscopy. Future prospective studies of patients with biopsy-proven NAFLD are required to confirm whether the severity of NAFLD increases risk of incident colorectal tumours.