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Review
. 2013 Dec 14;19(46):8780-8.
doi: 10.3748/wjg.v19.i46.8780.

Smoking, alcohol consumption, and the risk of extrahepatic cholangiocarcinoma: a meta-analysis

Xiao-Hua Ye  1 , Jia-Ping Huai  1 , Jin Ding  1 , Yan-Ping Chen  1 , Xue-Cheng Sun  1
Affiliations
Review

Smoking, alcohol consumption, and the risk of extrahepatic cholangiocarcinoma: a meta-analysis

Xiao-Hua Ye et al. World J Gastroenterol. .

Abstract

Aim: To assess the association between smoking and alcohol consumption and extrahepatic cholangiocarcinoma (ECC) through a meta-analysis of clinical observational studies.

Methods: A literature search was conducted using Embase and MEDLINE databases from inception to 31 May 2013 without language limitations, and by manually searching the references of retrieved articles. Case-control and cohort studies that investigated the association between smoking or alcohol consumption and ECC were included. The quality of these studies was assessed using the Newcastle-Ottawa quality assessment scale. Summary relative risks and corresponding 95%CI were calculated using a random-effects model. Publication bias was assessed by Begg's funnel plot and Egger's test.

Results: A total of 12 eligible articles (11 case-control studies and one cohort study) were included in this meta-analysis. Eleven studies reported the association between smoking and ECC. Pooled analysis indicated that smokers had an increased risk of ECC development as compared with non-smokers (summary RR = 1.23; 95%CI: 1.01-1.50). This correlation was present in population-based studies (n = 5; summary RR = 1.47; 95%CI: 1.06-2.05) but not in hospital-based studies (n = 6; summary RR = 1.10; 95%CI: 0.88-1.37) and in non-Asian regions (n = 7; summary RR = 1.39; 95%CI: 1.03-1.87) but not in Asia (n = 4; summary RR = 1.08; 95%CI: 0.85-1.38). Seven studies reported an association between consuming alcohol and ECC. Pooled analysis indicated that alcohol drinkers had a similar risk of ECC development as did individuals who did not drink alcohol (summary RR = 1.09; 95%CI: 0.87-1.37). There was moderate heterogeneity among the studies and no evidence of publication bias.

Conclusion: Smoking is associated with an increased risk of ECC, but alcohol consumption is not. Further population-based studies, particularly cohort studies, are warranted to enable definitive conclusions.

Keywords: Alcohol consumption; Extrahepatic cholangiocarcinoma; Meta-analysis; Relative risk; Smoking.

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Figures

Figure 1
Figure 1
Flow chart of the study selection.
Figure 2
Figure 2
Relative risk of extrahepatic cholangiocarcinoma. A: Smokers as compared with non-smokers in population- and hospital-based case-control studies; B: Alcohol drinkers as compared with non-alcohol drinkers in case-control and cohort studies.
Figure 3
Figure 3
A Begg’s funnel plot with pseudo 95% confidence limits showing the symmetrical distribution of included studies. This indicates that there was no publication bias.
Figure 4
Figure 4
Influence of each individual study on the relative risks of extrahepatic cholangiocarcinoma in smokers as compared with non-smokers. Data show the RR (open circle) and 95%CI (dashed horizontal line) when the study named on the left was omitted. Random-effects estimates (exponential form) were used. RR: Relative risk.
Figure 5
Figure 5
Proposed mechanisms by which smoking may be associated with the formation of extrahepatic cholangiocarcinoma.
See this image and copyright information in PMC

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