Secular Trends in the Incidence of Cholangiocarcinoma in the USA and the Impact of Misclassification

Background and Aims It has been reported that the incidence of intrahepatic cholangiocarcinoma (ICC) has increased in the USA, while extrahepatic cholangiocarcinoma (ECC) has decreased or remained stable. However, neither the recent trends nor the effects of the misclassification of Klatskin tumors are known. Methods Using the Surveillance, Epidemiology, and End Results program databases, we calculated the average annual age-adjusted incidence rates (AA-IRs) of ICC and ECC in 4-year time periods (1992–1995, 1996–1999, 2000–2003, 2004–2007). These AA-IRs were calculated with misclassified as well as correctly classified Klatskin tumors. AA-IRs were also calculated based on age, sex, and race. Multivariable Poisson regression models were used to evaluate the secular trends of ICC and ECC. Results The AA-IR of ICC was 0.92 in 1992–1995 and 0.93 in 2004–2007, while the AA-IR of ECC increased from 0.70 in 1992–1995 to 0.95 in 2004–2007. There was no significant trend in AA-IR of ICC ( p = 0.07), while there was a significant increase in ECC across the 4-year time periods ( p