Hepatitis B virus and the control of hepatocellular carcinoma.

There is now a substantial body of evidence that, in a very high percentage of cases, infection with hepatitis B virus (HBV) is required for the development of hepatocellular carcinoma (HCC), which is one of the most common cancers in the world. In vast areas of Asia, Africa and Oceania it is one of the commonest cancers in males, and it has been estimated that overall there are as many as 1 million deaths a year from this disease. HBV can be identified in over 90% of cases of HCC. In most or all of these the HBV DNA is integrated into the DNA of the host cell. Individuals who are HBV carriers for a long period, in certain regions, particularly if infected in their youth, have about a 200-fold greater risk of developing cancer than those who have not been chronically infected. This makes the HBV carrier group the highest known risk category for a common cancer. A vaccine to prevent infection with HBV has been introduced and is now available and in use in the United States, Europe, Asia and Africa. Public health programmes are currently being planned, or are in progress, for the vaccination of newborn children in areas where HBV infection is endemic. It is hoped that in a relatively short time this will considerably decrease the incidence of HBV carriers and, in due course, markedly decrease the incidence of HCC. The effectiveness of these programmes in reducing the carrier rate should be known in a few years. Extensive field trials with the vaccine have shown that it is highly effective and, based on these initial studies, extremely safe. A variety of steps are now being undertaken to markedly reduce its cost. This should make it possible to use it in the areas of Asia, Africa and Oceania where the greatest need exists. An internationally funded programme could be very effective in speeding the application of the vaccine. There are now several hundred million carriers of HBV in the world, many of whom are at high risk of developing HCC. Current research is directed towards understanding the pathogenesis of HCC in these individuals with the hope that the development of the cancer can be prevented or markedly delayed. This research could provide a form of secondary prevention for the high-risk population. If successful, it could have an immediate effect in decreasing the incidence of HCC mortality and morbidity.