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

Table 1 Characteristics of the 12 studies that reported an association between smoking or alcohol consumption and the risk of extrahepatic cholangiocarcinoma

Author and year	Country	Design	Source	Number of cases	Number of controls	Risk factor assessment	ECC ascertainment	Smoking RR (95% CI)	Alcohol RR (95% CI)	Adjustments
Ghadirian et al[18] 1993	Canada	Case-control	Population	24	239	Questionnaire	NA	2.820 (1.010-7.860)	-	Age, sex, other smoking habits, alcohol consumption, schooling, respondent status
Chow et al[19] 1994	United States	Case-control	Population	64	255	Questionnaire	Pathological	1.630 (0.900-2.970)1	0.600 (0.290-1.220)1	Age, ethnic origin, smoking status (adjusted for alcohol consumption)
Khan et al[20] 1999	United States	Case-control	Hospital	31	138	Medical records	Pathological	0.630 (0.210-1.880)	-	Age, female gender, ethnicity, cholelithiasis, socioeconomic status
Zhang et al[21] 2004	China	Case-control	Population	99	373	Questionnaire	Cancer registry	1.490 (0.870-2.560)2	1.290 (0.780-2.170)2	Age, total energy, cholelithiasis, hypertension, history of salty food intake, smoking status (adjusted for alcohol consumption)
Welzel et al[11] 2007	United States	Case-control	Population	549	102782	Medical records	Cancer registry	1.700 (1.000-3.000)	-	Age, sex, race, geographic location, state buy-in status
Shaib et al[10] 2007	United States	Case-control	Hospital	163	236	Medical records	Pathological + imaging	1.300 (0.800-1.900)3	1.290 (0.190-8.910)1	Race, age, gender, HBV, HCV markers (adjusted for alcohol consumption)
El-Serag et al[22] 2009	United States	Cohort	-	-	-	Registry	Cancer registry	-	1.060 (0.600-1.870)	Age, sex, baseline visit date, type of visit, a preceding visit
Tao et al[23] 2010	China	Case-control	Hospital	129	380	Medical records	Pathological + imaging	0.900 (0.500-1.300)3	1.200 (0.800-1.900)3	-
Cai et al[24] 20114	China	Case-control	Hospital	313	608	Medical records	Pathological	0.900 (0.640-1.248)3	-	-
Onal et al[25] 2012	Turkey	Case-control	Hospital	89	48	Questionnaire	Pathological + imaging	1.900 (0.900-4.200)3	4.010 (0.480-33.62)3	-
Brandi et al[26] 2013	Italy	Case-control	Population	59	212	Questionnaire	Pathological	0.780 (0.400-1.500)	-	Age, sex, region of residence
Zhou et al[27] 2013	China	Case-control	Hospital	239	478	Medical records	Pathological + imaging	1.301 (0.863-1.962)	1.053 (0.670-1.655)	Age, sex, cirrhosis, cholelithiasis, cholecystectomy, DM, family history of other cancer

¹The summary RRs and 95%CI were derived by pooling the relative risks for each sex;

²Only males were included in the summary relative risks because of the rarity of smoking in females;

³Univariate OR was calculated because adjusted ORs were not available;

⁴Only hilar cholangiocarcinomas were included; ECC: Extrahepatic cholangiocarcinoma; HBV: Hepatitis B virus; HCV: Hepatitis C virus; DM: Diabetes mellitus; NA: Not available.