Helicobacter bilis in human gallbladder cancer: results of a case-control study and a meta-analysis

Gallbladder cancer is an uncommon neoplasm of uncertain etiology and poor survival. Recently, interest has been generated in bacterial infections and cancers. Helicobacter is one such bacterium found to be associated with gastric MALToma, gastric adenocarcinoma and hepatobiliary neoplasms.Fifty four gallbladder cancer and 55 controls with cholelithiasis were studied. Helicobacter bilis was identified using 16S rRNA PCR. Relative risk and odds ratio with 95% CI were estimated. A detailed search of literature was carried out and selected relevant articles were extracted. A meta analysis was carried out using a random effect model.Helicobacter bilis was identified in 32/54 patients and 32/55 controls, The relative risk of gallbladder cancer in H. bilis positive cases was 1.05 (95% CI 0.49 to 2.24). Of the 10 identified case control studies on Helicobacter in the hepatobiliary tract 3 each were on gallbladder cancer and H. bilis. In meta analysis a pooled odds ratio of 4.13 (95% CI 2.68-6.36) favoring Helicobacter was observed. Pooled analysis of published studies on gallbladder cancer showed an odds ratio of 1.24 (95% CI 0.63-2.44).The present study failed to demonstrate any increase in risk of gallbladder cancer in presence of Helicobacter bilis. It may be hypothesized that increased risk observed in earlier studies may be indirectly due to increase in the risk of gallstones, although lack of any study specifically looking at this aspect and absence of normal controls in the present study makes this assumption superfluous.