Hepatitis B virus genotypes and hepatocellular carcinoma in Japan

Hepatitis B virus (HBV) is one of the major causative agents of hepatocellular carcinoma (HCC) in Southeast Asia where HBV genotype B (HBV/B) and genotype C (HBV/C) are prevalent. Clinical and virological differences were evaluated between HCC patients in Japan and Taiwan, all of whom were infected with HBV/B and HBV/C. In Japan, the prevalence rates of HBV/B and HBV/C were 12 and 85%, respectively, in patients with chronic HBV infection, which is similar to those of 13 and 86% in patients with HCC. In the HCC patients with HBV/B, the mean age was 70 years and higher than that of 55 years in those with HBV/C. In Taiwan, however, HBV/B was detected in 61% and HBV/C in 31% of patients with HCC. Furthermore, the mean age of HCC patients with HBV/B in Taiwan was 50 years and younger compared to the 59 years of those with HBV/C. These differences may be explained by a distinct distribution of subtypes of HBV/B between the two countries. In Taiwan as well as in most Asian countries only the subtype Ba of HBV/B is found, while the majority of Japanese patients with HBV/B have the subtype Bj. Although the risk factors associated with HCC should be investigated with respect to host and environmental factors, the differences in genotypes and subtypes of HBV would need to be taken into consideration in etiological and clinical studies on HCC.