Meta-analysis of alcohol consumption and risk of extrahepatic bile system cancer

Aim: Alcohol consumption increases the risk of liver cancer. However, there is still controversy regarding alcohol consumption and the risk of extrahepatic bile system cancer (EBSC). We performed a meta-analysis to provide an overview of the relevant studies and gain more robust estimates of the relationship between alcohol consumption and risk of EBSC. Methods: Relevant studies published between January 1966 and October 2010 were identified by searching Medline, Embase and the Cochrane Library. Studies were selected using a priori defined criteria. The strength of the relationship between alcohol consumption and risk of EBSC was assessed by adjusted odds ratio (OR). Results: A total of 113767 participants from 10 studies (nine case-control studies and one cohort study) were identified in this meta-analysis. The studies provided adjusted overall OR estimates for drinkers versus non-/low drinkers, leading to a pooled adjusted OR of 0.82 (95% confidence interval [CI]=0.72-0.94, P for heterogeneity=0.194, I2=27.2%). The overall adjusted OR of hospital-based studies and population-based studies were 0.80 (95% CI=0.65-0.99, P=0.260) and 0.79 (95% CI=0.64-0.98, P=0.119), respectively. For the heavy drinkers, the adjusted OR significance increased to 1.58 (95% CI=0.97-2.57, P for heterogeneity=0.055, I2=65.4%), but it had no statistical significance. Conclusion: There is evidence that moderate alcohol consumption lowers the risk of EBSC compared with non-/low alcohol consumption, but not heavy alcohol consumption. Further multicenter and better controlled studies are required to confirm these findings.