title: Risk factors for intrahepatic and extrahepatic cholangiocarcinoma in the United States: a population-based case-control study.
abstract: OBJECTIVE
  Intrahepatic and extrahepatic cholangiocarcinomas are rare and highly malignant cancers of the bile duct. Although the incidence of extrahepatic cholangiocarcinoma (ECC) has remained constant, the incidence of intrahepatic cholangiocarcinoma (ICC) has increased in the United States. Because the etiology of both tumors is poorly understood, a population-based case-control study was conducted to examine the association of ECC and ICC with preexisting medical conditions.
  
  
  METHODS
  Medical conditions among 535 ICC patients, 549 ECC patients (diagnosed 1993-1999), and 102,782 cancer-free controls were identified by using the Surveillance, Epidemiology and End Results-Medicare databases. Logistic regression analysis was used to calculate adjusted odds ratios.
  
  
  RESULTS
  In addition to established risk factors (choledochal cysts, cholangitis, inflammatory bowel disease), several other conditions were significantly associated with ECC and ICC: biliary cirrhosis (ECC, ICC: P < .001), cholelithiasis (ECC, ICC: P < .001), alcoholic liver disease (ECC, P < .001; ICC, P = .01), nonspecific cirrhosis (ECC, ICC: P < .001), diabetes (ECC, ICC: P < .001), thyrotoxicosis (ECC, P = .006; ICC, P = .04), and chronic pancreatitis (ECC, ICC: P < .001). Conditions only associated with ICC were obesity (ECC, P = .71; ICC, P = .01), chronic nonalcoholic liver disease (ECC, P = .08; ICC, P = .02), HCV infection (ECC, P = .67; ICC, P = .01), and smoking (ECC, P = .07; ICC, P = .04).
  
  
  CONCLUSIONS
  Several novel associations with ECC and ICC were identified. HCV infection, chronic nonalcoholic liver disease, and obesity, all of which are increasing in incidence, and smoking were associated only with ICC, suggesting that these conditions might explain the divergent incidence trends of the tumors.
authors: Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland, USA.
authors: Tania M
authors: TM
authors: Welzel
authors: Barry I
authors: BI
authors: Graubard
authors: Hashem B
authors: HB
authors: El-Serag
authors: Yasser H
authors: YH
authors: Shaib
authors: Ann W
authors: AW
authors: Hsing
authors: Jessica A
authors: JA
authors: Davila
authors: Katherine A
authors: KA
authors: McGlynn
mesh_terms: D000368:Aged; D001650:Bile Duct Neoplasms / Q000453:epidemiology*; D017734:Bile Ducts, Extrahepatic; D001653:Bile Ducts, Intrahepatic; D018281:Cholangiocarcinoma / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D011159:Population Surveillance; D012189:Retrospective Studies; D012307:Risk Factors; D018426:SEER Program / Q000706:statistics & numerical data*; D015996:Survival Rate; D014481:United States / Q000453:epidemiology
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