Epidemiology of chronic hepatitis B virus infection, hepatocellular carcinoma, and hepatitis B virus-induced hepatocellular carcinoma.

Approximately 360 million people worldwide are chronically infected with hepatitis B virus (HBV) and are at high risk of developing hepatocellular carcinoma (HCC). Chronic HBV infection is the most prevalent cause of this tumour, accounting for 55% of global cases, and 89% of those in endemic regions for HBV infection. Relative risks for developing HCC in the presence of chronic HBV infection may be as high as 49 in case-control studies, and 98 in cohort studies. HCC is the sixth most common cancer in the world today, with approximately 630,000 new cases occurring each year. It ranks third in annual cancer mortality rates. Approximately 80% of HCCs occur in developing countries where HBV infection is endemic, with the highest incidences being in the Asia-Pacific region, and sub-Saharan Africa. In the chronic carriers of the virus who are at greatest risk of developing HCC, the infection is acquired at birth or in the early months or years of life, either perinatally or horizontally, and frequently becomes chronic. The risks are greater in males, and older individuals, and are increased by co-exposure to aflatoxin B(1), the presence of cirrhosis, obesity, or diabetes mellitus, and possibly co-infection with hepatitis C virus. Viral factors that influence the risk of HCC are high viral load, the presence of certain mutations, and genotypes. Although the incidence of chronic HBV infection is beginning to decrease as a result of the universal infant immunization programme, HBV-induced HCC incidence is projected to increase for at least another two decades.