Comparison of Incidence of Intrahepatic and Extrahepatic Cholangiocarcinoma - Focus on East and South-eastern Asia

Background: The term “cholangiocarcinoma” was originally used only for intrahepatic bile duct (adeno)carcinomas, but is now regarded as inclusive of intrahepatic, perihilar, and distal extrahepatic tumors ofthe bile ducts. A rise in incidence of intrahepatic cholangiocarcinoma has been recently reported in Westerncountries but comparatively little is known about recent cholangiocarcinoma incidence trends in East andSouth-Eastern Asia.
Methods: We compared age-adjusted incidence rates of both intrahepatic and extrahepaticcholangiocarcinomas, as well as coding practices, using data from 18 cancer registries in Asia and 4 selectedregistries in Western countries. Intrahepatic cholangiocarcinoma incidence rates were calculated after reallocationof cases with unknown or unspecified histology among liver cancer cases.
Results: Age-adjusted incidencerates of intrahepatic cholangiocarcinoma varied by more than 60-fold by region. The highest rates were foundin Khon Kaen, Thailand, where 90% of liver tumors were cholangiocarcinomas. The next highest rates werefound in the People’s Republic of China, followed by the Republic of Korea. The highest age-adjusted incidencerate for extrahepatic cholangiocarcinoma was found in Korea. Coding practices for perihilar (Klatskin tumor)or unspecified sites of cholangiocarcinoma differed from one cancer registry to the other. The proportion ofKlatskin tumors among cholangiocarcinomas was less than the one reported in clinical settings.
Conclusion:Developing a consistent and uniform topographical classification for acceptable coding practice to all healthprofessionals is necessary. In addition, epidemiological research on risk factors according to anatomical location(intrahepatic versus extrahepatic) and the macroscopic appearance and/or new histological classification ofcholangiocarcinoma is also needed.