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This is a brief summary of the considerable variation of malignant disease throughout the tropical world, which is not only of importance to the diagnostic radiologist, but may help in unraveling the etiology of many types of cancer. There are many difficulties; this chapter has been an oversimplification of immense variations. Sometimes the geographic difference in incidence is so marked that the possibility of error is slight. For example, the difference in frequency between carcinoma of the esophagus in West Africa and southern Africa is so great that it is beyond dispute: there is no way in which population distribution, age variations, medical care, or other factors could cause this disparity. In other instances, there is undoubtedly a bias due to the local interest of a particular reporting physician, the willingness or unwillingness of local people to come for treatment (Fig. 43.16) (especially women, whose religion and customs may forbid visits to male physicians), the sophistication of the available medical services (particularly the pathological interpretation), and the autopsy rate. Factors such as these account for some of the local variations within small distances, but not for all of them. Wherever there is a racial mixture (e. g., whites, Asians, and blacks in the same country) there is nearly always a similar unexpected variation in the incidence of many types of malignancy. To make interpretation more difficult, the published figures from various areas are not always comparable with regard to many of the histological types of cancer. The World Health Organization is establishing diagnostic criteria for specific malignancies and thus reducing the individual variation between pathologists. On the other hand, the spread of AIDS is changing almost all the statistics.

But, despite all the difficulties, the correctness of the overall thesis is indisputable. There is a considerable geographic and local variation of malignant disease which must have great significance, and the individual radiologist has an important, indeed essential, part to play in recording these differences in addition to using the information for the benefit of individual patients.

Fig. 43.16. Even when the patient can be persuaded to try Western medicine, and all the arrangements are made with the radiotherapy oncology center, it is still not certain that treatment will be given, as this telegram shows.

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Copyright: Palmer and Reeder