Primary prevention of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is one of the major cancers in China. Accordingly, the mortality rates in 1990 (per 100,000) were 20.10 in certain cities and 24.32 in certain counties. More than 90% of HCC cases and 70% of controls were infected with the hepatitis B virus (HBV) (Odds Ratio (OR) = 10-50). In the same group of patients, 8-27% of those with HCC and 0-11% of the healthy controls were also infected with hepatitis C (HCV) (OR = 2.11-17.29). There appears to be some correlation between HBV markers and the OR. The government requires that 85% of infants be immunized with HBV vaccine. In 1992, there were 3 million infants inoculated with HB vaccines. Aflatoxins have been found as contaminants in food, particularly in corn, peanut oil, soya sauce and fermented soya beans. The intake of aflatoxin B1 (AFB1) by people of ten different villages correlated with HCC mortality rates (r = 0.55; P < 0.05). The concentration of AFB1-albumin adducts is an indicator of individual exposure to aflatoxins. These adducts are higher in hyperendemic HCC areas and cases. Most people have now changed their staple food and eat rice instead of corn. Six large epidemiological studies have confirmed that people who drink pond-ditch water experience higher HCC mortality rates than people who drink deep-well water. Recent research has found that the blue-green algal toxin microcystin (MCYST) was a contaminant of pond-ditch water. MCYST is a strong promoter of HCC and will induce severe intrahepatic haemorrhages and liver necrosis. More than 80% of people in Qidong County have already changed their sources of water from pond-ditches to deep wells. Therefore, a combined strategy of the prevention of hepatitis, control of crops and control of drinking water is advocated for the primary prevention of HCC in China.