Survey of Human Cancer Based upon Parental Age

Cancer incidence is associated with the "ageing process." It is frequently stated that cancer is a disease of old age. This idea is based primarily upon the fact that both skin carcinoma and carcinoma of the breast increase in frequency with advancing age. In this case the relative frequency remains about the same. It has been maintained that the great increase in cancer mortality at the present time is due in part to the increased average expectancy of life in man. The ageing of the individual may contribute toward the ageing of species to which the individual belongs. However, this theory is not supported by experimental evidence but it should not be dogmatically dismissed. It is not too much to keep in mind, therefore, that the ancestral descent, including parents and grandparents, may possibly contribute to cancer susceptibility in the individual. The increased expectancy of life or longevity has been due to several causes among which may be mentioned the improvement in the treatment of diseases of infancy, advancements in medical care, and the improvement of public health by sanitation, immunization, and other practices. The recent introduction of antibiotics has already influenced the average expectancy of life. It is probably true that the life expectancy at sixty is about the same now as it was fifty years ago. The nature of man has not changed, although Pearson has maintained that there has been a selective survival-time influence during the past three centuries, the greater proportion of the population belonging to large families derived from parents who lived beyond the average expectancy of life. The problem of longevity is a complex one. The forces at play are intrinsic or genetic and environmental. Again cancer susceptibility, in both experimental animals and in man, is a complex variable. It is probably unwise to draw final correlations between two complex systems. It becomes necessary, therefore, to resolve the problems of the expectancy of life and of cancer susceptibility into their component parts.