title: Geographic variation of intrahepatic cholangiocarcinoma, extrahepatic cholangiocarcinoma, and hepatocellular carcinoma in the United States.
abstract: BACKGROUND
  Intrahepatic (ICC) and extrahepatic cholangiocarcinomas (ECC) are tumors that arise from cholangiocytes in the bile duct, but ICCs are coded as primary liver cancers while ECCs are coded as biliary tract cancers. The etiology of these tumors is not well understood. It has been suggested that the etiology of ICC is more similar to that of another type of liver cancer, hepatocellular carcinoma (HCC), than to the etiology of ECC. If this is true, geographic incidence patterns and trends in ICC incidence should be more similar to that of HCC than ECC.
  
  
  METHODS
  To examine this hypothesis, data from the North American Association of Central Cancer Registries Cancer in North America data file were analyzed. Incidence rates and joinpoint trends were calculated by demographic subgroup. County-level incidence rates were mapped.
  
  
  RESULTS
  Overall incidence rates, racial distribution, male:female ratio, and peak ages were more similar between ICC and ECC than with HCC. During 2000-2009, average annual incidence rates of ECC increased. During 2005-2009, average annual ICC incidence rates also increased. High rates for all three cancer sites were found in the Pacific region, particularly Hawaii and Alaska. Rates of ICC and ECC were also high in the Northeast and the upper Midwest, while rates of HCC were high in the South.
  
  
  CONCLUSIONS
  Demographic patterns and geographical variation were more closely related between ICC and ECC than HCC, suggesting that the etiology of ICC and ECC may be similar. Increasing rates of both tumors suggest that further etiology studies are warranted.
authors.affiliation: Division of Cancer Control and Population Sciences, National Cancer Institute, Rockville, Maryland, United States of America.
authors.forename: Sean F
authors.initials: SF
authors.lastname: Altekruse
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD, United States of America.
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Petrick
authors.affiliation: Division of Cancer Control and Population Sciences, National Cancer Institute, Rockville, Maryland, United States of America.
authors.forename: Alicia I
authors.initials: AI
authors.lastname: Rolin
authors.affiliation: Information Management Services, Inc., Calverton, MD, United States of America.
authors.forename: James E
authors.initials: JE
authors.lastname: Cuccinelli
authors.affiliation: Information Management Services, Inc., Calverton, MD, United States of America.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Zou
authors.affiliation: Division of Cancer Control and Population Sciences, National Cancer Institute, Rockville, Maryland, United States of America.
authors.forename: Zaria
authors.initials: Z
authors.lastname: Tatalovich
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD, United States of America.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: McGlynn
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001650:Bile Duct Neoplasms / Q000453:epidemiology*; D006528:Carcinoma, Hepatocellular / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D018281:Cholangiocarcinoma / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008113:Liver Neoplasms / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D012042:Registries; D062211:Spatio-Temporal Analysis; D014481:United States / Q000453:epidemiology; D055815:Young Adult
references.citation: Clin Gastroenterol Hepatol. 2007 Oct;5(10):1221-8
references.pmid: 17689296
references.citation: Am J Gastroenterol. 2007 May;102(5):1016-21
references.pmid: 17324130
references.citation: Cancer Epidemiol Biomarkers Prev. 2011 Apr;20(4):591-9
references.pmid: 21266522
references.citation: J Hepatol. 2012 Apr;56(4):848-54
references.pmid: 22173164
references.citation: Gastroenterology. 2012 May;142(6):1264-1273.e1
references.pmid: 22537432
references.citation: J Gastroenterol Hepatol. 2012 Oct;27(10):1561-8
references.pmid: 22694354
references.citation: Am J Gastroenterol. 2014 Apr;109(4):542-53
references.pmid: 24513805
references.citation: Cancer. 2000 Jun 1;88(11):2471-7
references.pmid: 10861422
references.citation: Cancer. 1993 Aug 1;72(3):683-8
references.pmid: 8192727
references.citation: Int J Epidemiol. 1996 Oct;25(5):933-40
references.pmid: 8921477
references.citation: Ann Oncol. 1999;10 Suppl 4:308-11
references.pmid: 10436847
references.citation: J Natl Cancer Inst. 2006 Jun 21;98(12):873-5
references.pmid: 16788161
references.citation: Liver Int. 2006 Nov;26(9):1047-53
references.pmid: 17032404
references.citation: CA Cancer J Clin. 2007 Jan-Feb;57(1):30-42
references.pmid: 17237034
references.citation: J Clin Oncol. 2009 Mar 20;27(9):1485-91
references.pmid: 19224838