Variations in National Patterns of Cancer Incidence and Mortality

Abstract

Geographic differences in the amount and site distribution of cancer were first reported about the turn of the century, and although some of these observations and impressions could not be supported later and others had to be reinterpreted, there is now considerable evidence that significant differences exist between various countries in both cancer incidence and cancer mortality. An important aspect of the study of national differences is the identification of unusual tumours found in various parts of the world. The first interpretation of these unusual tumours was that they were “racial” and dependent on a special susceptibility, probably hereditary. It has been reported, for example, that the Indian was susceptible to betel-nut carcinoma, the Chinese to nasopharyngeal carcinoma, the European to gastric cancer and, more recently, the African Bantu to hepatoma. It now appears that these deductions were premature, for the more “racial” cancers are studied, the more apparent it becomes that they are not actually “racial” in the exact sense of the word. What appears at first to be “racial” in the genetic sense tends upon further examination to be “racial” only in the cultural or special environmental sense. The resistance of the Jew to cancer of the penis represents not inherent immunity of the cells but the consequence of the cultural custom of early circumcision. Similarly, the Negro has a low frequency of cutaneous carcinoma not because his cells are non-susceptible but because they are shielded by melanin from the commonest carcinogen.