The use of epidemiology, scientific data, and regulatory authority to determine risk factors in cancer of some organs of the digestive system. 2. Esophageal cancer.

The epidemiologic aspects of esophageal cancer are well known. The extreme geographical variations in incidence of the disease, the variability in the sex ratio, and the secular trends have been described frequently. The etiology of cancer of the esophagus is known to be complex and composed of multiple factors, those caused by the environment being of greatest importance. The disease preferentially attacks groups with a low socioeconomic status or those hindered by poverty. The esophageal cancer belt has been frequently studied to provide clues to the etiology of esophageal cancer but no definite culprit has yet been found. The majority of the factors so far implicated in cancer of the esophagus appear to act directly on the esophagus rather than systemically. This is an unusual situation in that it enables the disease to be prevented by primary means. There appears to be an enormous disparity in the etiology of the disease among various countries. This disparity may be more apparent than real if the epidemiologic data are interpreted to mean that there is a two-stage process involved, with multiple etiologies for each stage. If we assume that nutritional deficiencies, even subtle ones, predispose the esophagus to influence by carcinogenic substances, the geographic differences fade. Nutritional deficiencies can develop by chronic alcohol use as well as by poverty and lack of an adequate food supply, but diet does not explain the whole picture. External carcinogens are necessary to effect the end result. The culprit may be tobacco in one culture and fungal elements in another. The South African studies which showed an association with tobacco and not alcohol could be explained if we assume that the population's nutritional deficiencies already predisposed the esophagus for the effect of an external carcinogen, thereby making alcohol usage superfluous. It would be helpful if the relationship between esophagitis and nutritional status were elucidated and if it were determined that the condition could be improved or eliminated by dietary factors. The association between nutrition and esophagitis may suggest methods of primary prevention of esophageal cancer and provide a chance of lowering the incidence of this deadly disease.