Geographical variation in cancer incidence: A clue to causation

Conclusion

The observations on which our knowledge of the geographical variation in the incidence of cancer is based began to be made by surgeons in the last century who, working first in one country and then in another, realized that the pattern of disease with which they had to deal varied with the society in which they worked. Gross differences were readily accepted, like that reported less than 2 years after Grey Turner's birth between the vale of Kashmir, where Maxwell and Elmslie found that 42 out of 54 epitheliomas (78%) occurred on the skin of the abdomen or thigh, and European countries, where none were reported on these sites in a series of 220 cases [28]; however, smaller differences were not accepted.

The uneven availability of medical services and the disparity in birth and death rates, which produced major differences in the age distribution of different populations, made accurate comparisons impossible and the range of permissible opinion varied from the belief that cancer occurred equally everywhere at the same ages to the belief that the great majority of cases were produced by industrialization. Now, thanks to the development of cancer registries, it has been possible to put the matter beyond doubt and to demonstrate unequivocal differences, some of which are certainly attributable to industrialization, which has sometimes led to the development of the disease and sometimes to its elimination. We know, too, that careful observations, like those made by Denis Burkitt and the hundreds of surgeons and physicians who have collaborated with him throughout Africa, are capable of providing an indication of the relative frequency of different cancers that can provide valuable clues, even in the absence of precise figures for the size of the population served.

If this Congress is able to stimulate the collection of similar figures that will fill in the remaining gaps of the cancer map of the world, it may well make an important contribution to our knowledge of the causes of the disease and the way it can be prevented.