© The Author 2007. Published by Oxford University Press.
CORRESPONDENCE |
Re: Impact of Classification of Hilar Cholangiocarcinomas (Klatskin Tumors) on Incidence of Intra- and Extrahepatic Cholangiocarcinoma in the United States
Affiliations of authors: University College London Institute of Hepatology, Bloomsbury Campus, Royal Free & University College School of Medicine, London, UK (WRM, SPP); Liver Unit, St Mary's Hospital Campus, Imperial College London, London, UK (SAK)
Correspondence to: Wolf-Rudiger Matull, MD, MRCP, University College London Institute of Hepatology, Bloomsbury Campus, 69-75 Chenies Mews, London WC1E 6HX, UK (e-mail: w.matull{at}ucl.ac.uk).
Welzel et al. (1) highlight the inconsistencies in the coding of cholangiocarcinomas according to location in the International Classification of Diseases for Oncology, 2nd and 3rd editions (ICD-O-2 and ICD-O-3). ICD-O-2 automatically cross-referenced hilar cholangiocarcinomas "wrongly" to the intrahepatic topography code. This proved to have had an impact on the age-adjusted incidence rates for intra- and extrahepatic cholangiocarcinomas in the United States between 1992 and 2000, using data from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) cancer registry program. The 2000 World Health Organization's classification of tumors (2), which defines hilar cholangiocarcinomas as extrahepatic, was used by Welzel et al. as reference for the correct topography coding. A recent 2005 Lancet seminar on cholangiocarcinomas (3) still classified hilar cholangiocarcinomas as intrahepatic. It appears as if location inconsistencies occur not only with different versions of the ICD-O classifications but also between medical experts.
During the period when the ICD-O-2 was used, 91% of hilar cholangiocarcinomas from the SEER data were coded as intrahepatic. Interestingly, with ICD-O-3, in which either intra- or extrahepatic location could have been chosen, less than half of the hilar cholangiocarcinomas were coded "correctly" as extrahepatic. This difference suggests that coding of cholangiocarcinomas over the past 30 years into simple intra- or extrahepatic is unsatisfactory.
Approximately two-thirds of all cholangiocarcinomas are located at the liver hilum (4), i.e., at the bifurcation of the hepatic duct (Klatskin tumors). Patients are often diagnosed with hilar cholangiocarcinomas after the liver is invaded (i.e., Bismuth types 3 and 4) (5), and at this point, the disease appears similar to an intrahepatic tumor on diagnostic imaging. Thus, the accuracy of coding appears to be least clear for tumors that occur in the most common cholangiocarcinoma location.
Over the last 30 years, a steep increase in the incidence of intrahepatic cholangiocarcinoma has been documented in different parts of the world, with an associated (lesser) decline in extrahepatic cholangiocarcinoma (6,7). However, these studies used the same ICD-O codes and therefore will contain similar topography inconsistencies. Although the overall incidence of cholangiocarcinoma appears to be rising and is currently the subject of intense investigation, whether this is due to a rise in intra- and/or extrahepatic cholangiocarcinoma remains unclear.
We believe a consistent classification worldwide is required for evaluating epidemiologic data with regard to cholangiocarcinoma pathogenesis and location. Because the majority of hilar cholangiocarcinoma has invaded the liver by the time of diagnosis, we favor maintaining the ICD-O-2 cross-referencing of hilar cholangiocarcinoma to an intrahepatic topography. However, developing a consistent topography-coding practice that is acceptable to all health professionals will be a big task.
REFERENCES
(1) Welzel TM, McGlynn KA, Hsing AW, O’Brien TR, Pfeiffer RM. (2006) Impact of classification of hilar cholangiocarcinomas (Klatskin tumours) on the incidence of intra- and extrahepatic cholangiocarinoma in the United States. J Natl Cancer Inst 98:873–5.
(2) In Hamilton SR and Aaltonen HL (Eds.). World Health Organization's classification of tumors: pathology and genetics of tumors of the digestive system (2000) (IARC Press, Lyon (France)).
(3) Khan SA, Thomas HC, Davidson BR, Taylor-Robinson SD. (2005) Cholangiocarcinoma. Lancet 366:1303–14.[CrossRef][ISI][Medline]
(4) De Groen PC, Gores GJ, LaRusso NF, Gunderson LL, Nagorney DM. (1999) Biliary tract cancers. N Engl J Med 341:1368–78.
(5) Chahal P and Baron TH. (2006) Endoscopic palliation of cholangiocarcinoma. Curr Opin Gastroenterol 22:551–60.[ISI][Medline]
(6) West J, Wood H, Logan RFA, Quinn M, Aithal GP. (2006) Trends in the incidence of primary liver and biliary tract cancers in England and Wales 1971-2001. Br J Cancer 94:1751–8.[CrossRef][ISI][Medline]
(7) Shaib YH, Davila JA, McGlynn K, El-Serag HB. (1994) Rising incidence of intrahepatic cholangiocarcinoma in the United States: a true increase? J Hepatol 40:472–7.
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J Natl Cancer Inst 2007 99: 407-408.
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