The association between parity and hepatocellular carcinoma (HCC) was studied using a data-base generated by linking 2 Swedish nation-wide registries; the Cancer Registry and the Fertility Registry. Among women born between 1925 and 1960, 133 patients with HCC recorded in the Cancer Registry between 1958 and 1984 were compared with 665 age-matched controls. In this nested case-control study there was no positive association between parity, age at first birth or frequency of twinning on the one hand, and risk of HCC on the other. It appears that the positive association between parity and HCC previously reported is limited to cases of HCC caused by chronic infection with hepatitis B virus; these cases represent only a small fraction of HCC cases in Sweden.
The incidence of primary hepatocellular carcinoma (PHC) in Greenland between 1960 and 1981 was determined and compared with the rate of this disease in Denmark. The annual age and sex rate (per 100,000) was not significantly different (overall, 1.9 vs. 2.2) despite a large difference in the prevalence of hepatitis B surface antigen (HBsAg) and anti-HBs markers of hepatitis. On the basis of a recent report of a very strong risk of PHC among male HBsAg carriers, 4.0 cases of PHC per year were expected in male Eskimos, but only 0.2 cases per year were observed. The incidence rates of other cancers suggested to be virally associated, including nasopharyngeal carcinoma, salivary gland cancer, and carcinoma of the cervix, were all high in Greenland compared to rates for the Danish population, and these high incidence rates are in accord with the markedly higher prevalences in Greenland Eskimos of viruses with which these other cancers have been associated. Thus Greenland Eskimos do not have a high incidence of PHC despite a high prevalence of HBsAg carriers, which suggests that other carcinogenic factors in this environment may be absent or that protective factors are present.