Incidence rates of intra- and extrahepatic cholangiocarcinomas in Denmark from 1978 through 2002.

Recent studies from several countries, including the United States, have indicated that the incidence rate of intrahepatic cholangiocarcinoma is increasing while that of extrahepatic cholangiocarcinoma is decreasing. We examined whether such opposing trends could be confirmed in Danish data. We computed the nationwide Danish incidence rates of intra- and extrahepatic cholangiocarcinomas from January 1, 1978, through December 31, 2002, with data from the high-quality Danish Cancer Registry. Incidence rates were standardized to the US population in 2000. The study included 1335 patients with intrahepatic cholangiocarcinoma and 1269 with extrahepatic cholangiocarcinoma. The Danish incidence rates of intra- and extrahepatic cholangiocarcinomas were nearly identical throughout the study period. From 1978 through 2002, the incidence rate of intrahepatic cholangiocarcinoma decreased from 1.27 (95% confidence interval [CI] = 0.96 to 1.58) to 0.46 (95% CI = 0.29 to 0.62) per 100,000 people, and the rate of extrahepatic cholangiocarcinoma decreased from 1.05 (95% CI = 0.77 to 1.34) to 0.74 (95% CI = 0.53 to 0.95). The median age at diagnosis decreased during the study period, and the proportion of localized cancers increased. The decrease in cholangiocarcinoma incidence rates cannot be explained by time trends in known risk factors (e.g., inflammatory bowel disease, diabetes, smoking, or thorotrast), but our findings are consistent with a common etiology for intra- and extrahepatic cholangiocarcinomas.