The epidemiology of cholangiocarcinoma.

The incidence rates of cholangiocarcinoma (CC) vary greatly among different areas of the world, and this variation is related to distribution of risk factors. Intrahepatic cholangiocarcinoma (ICC) and extrahepatic cholangiocarcinoma (ECC) have different epidemiological features. Recent data show that the incidence and mortality rates of ICC have been increasing in several areas around the world. On the other hand, the incidence and mortality rates of ECC have been decreasing. For example, in the United States, the age-adjusted incidence rates of ICC increased by 165% from 0.32 per 100,000 in 1975 to 1979 to 0.85 per 100,000 in 1995 to 1999, whereas ECC declined by 14%. In the meantime, there has been very little improvement in long-term survival, which remains dismal (3.5%). Men are affected 1.5 times more than women are, and Asians are affected almost 2 times more than whites and blacks. There are few well-established risk factors for CC, including primary sclerosing cholangitis, liver fluke infestations, hepatolithiasis, Thorotrast exposure, and choledochal cysts. None of these risk factors can explain the recent increasing trends of ICC in the United States. Some data, however, point to a potential role for chronic liver disease, hepatitis C, and probably hepatitis B infections in the development of ICC.