[Epidemiology of primary liver cancer in Japan].

In Japan, more than 90% of primary liver cancers consist of hepatocellular carcinoma (HCC), 80% of which is caused by chronic hepatitis C virus (HCV) infection, and the remaining 15% of which is caused by chronic hepatitis B virus (HBV) infection. The proportion of older patients among patients with HCC has been increasing in recent years because of the aging of the HCV-prevalent birth cohort born between 1925 and 1935. The cumulative risk of developing HCC among HCV carriers was estimated as 30% for males and 6% for females. Older age, being male, having a low platelet count, higher histological stage, genotype 1b, co-infection with HBV, heavy drinking and smoking increase the risk of developing HCC among patients with chronic HCV infection. Recent reports on the efficacy of interferon therapy on the incidence of HCC in Japanese patients with chronic hepatitis C demonstrate the importance of providing a screening system for chronic HCV infection and establishing a medical referral system so that patients undergo the appropriate therapy for the Japanese HCV carriers.