A case-control study on liver cancer with special emphasis on the possible aetiological role of schistosomiasis.

In order to elucidate the relationship between liver cancer and suspected aetiological factors, a case-control study was carried out at seven hospitals in Yamanashi prefecture, where the mortality rate of the disease was significantly higher than the corresponding national figure. This prefecture was also recognised as one of the endemic areas for Schistosoma japonicum in Japan. Sixty-two cases of liver cancer, and the same number of controls were selected during the two-year study period. A skin test for Schistosoma japonicum, serum tests for HB virus and a questionnaire study were carried out. The results of matched pair analysis revealed that liver cancer was significantly highly correlated with three factors, that is, HBs antigen (HBsAg), history of schistosomiasis, and daily intake of alcohol, and that their odds ratios were 10.0, 9.5 and 3.2 respectively. The values of percentage population attributable risk for these three factors were estimated to be 21.3%, 71.8% and 39.8% respectively. The above findings suggest that HBsAg and history of schistosomiasis are both important risk factors for liver cancer and that schistosomiasis may be much more important than HB virus in the area. The analysis of combinations of these three factors suggest that each factor might be related to liver cancer multiplicatively rather than additively.