Prospects for epidemiological studies on hepatocellular cancer as a model for assessing viral and chemical interactions.

Chronic infection with hepatitis B virus (HBV) accounts for 1-10% of hepatocellular carcinoma (HCC) in low-risk countries and for 56-94% in high-risk populations. However, although HBV is perhaps the second most important human carcinogen so far identified, chronic HBV infection is neither a sufficient nor a necessary cause of HCC. Other factors must be causally related to HCC, and some of them have been identified: aflatoxins, tobacco smoking, and use of alcohol and oral contraceptives. The evidence for an association between these factors and HCC is reviewed, as well as their joint effects. Finally, prospects for epidemiological research on HCC, and specifically the assessment of viral and chemical interactions, are discussed.