Susceptibility to cancer: some examples from epidemiology.

No population in the world is known to be resistant to cancer development, but there seems to be differences between individuals in susceptibility to cancer development following exposure to environmental carcinogenic risk factors. The age dependency of cancer may be interpreted both with regard to carcinogenic exposure and resistance to tumour development. Studies of migrant populations have pointed both to the fact that apparent resistance to cancer in certain populations is spurious, and to characteristic susceptibility to certain tumour types as for instance nasalpharangyal cancer and skin cancer. "Host factors"--either genetically in origin or environmentally induced--may be responsible for differences in susceptibility. It is concluded that there is abundant epidemiological evidence of the role of environmental factors in cancer causation, and that possible interactions between tumour-producing and risk modifying factors should be further exploited.