Helicobacter pylori infection and the risk of colorectal cancer: A meta-analysis of epidemiologic evidence.

Abstract

408 Background: The association between Helicobacter pylori infection (HPI) and gastric cancer is well known, but it is unclear whether HPI is also a risk factor for colorectal cancer. Several epidemiological studies on the latter association have yielded conflicting results. The aim of this study is to summarize available evidence on the association between HPI and CRC, evaluating its magnitude and direction in a meta-analysis. Methods: Two reviewers independently conducted a systemic search on Medline, OvidSP and PubMed databases from January 1980 to July 2011 for studies on the association between HPI and CRC. The reference lists of eligible studies were next reviewed for additional studies on the subject. Firstly, a combined analysis including all studies was done. Next, subgroup analysis by study design and country of study (USA Vs Europe Vs Asia) were also performed. All analyses were done using the random effects model. Publication bias was assessed using the Begg’s and Egger’s tests and visual inspection of funnel plot. All analyses were performed using STATA 11. Results: Sixteen studies (14 retrospective and 2 prospective) including 12,892 participants were included in the analysis. Overall, HP was associated with a 49% significantly higher risk of CRC (OR 1.49, 95% CI: 1.22-1.82; P < 0.001). By study design, the association persisted only among the retrospective studies with a pooled OR of 1.43 (95% CI: 1.31-1.56, P = 0.004). The subgroup analysis by study region showed significant associations in Europe (OR 1.35, 95% CI 1.09-1.66) and Asia (RR 1.43, 95% CI 1.29-1.58). Though there was a 17% higher risk noted among studies done in the USA, this was not statistically significant. There was no evidence of publication bias in all the analyses. Conclusions: Current evidence on the association between H. pylori infection and CRC remains inconclusive. The absence of any association among the prospective studies (with less risk of bias) suggests that the association seen among the retrospective studies could be due to residual confounding. Better quality data is required before a conclusive statement on the association between HPI and CRC can be made.