Chemoprevention of oral and esophageal cancer in Uzbekistan, Union of Soviet Socialist Republics.

The results of a survey of a population with a high risk of oral and esophageal cancer and the outline of a chemoprevention scheme for persons found to have a precancerous condition of the mouth and esophagus are presented. Of a total of 1,569 men examined, 11% had preleukoplakia and leukoplakia of the mouth, and 60% of the 1,344 men in whom esophagogastroscopy was performed had chronic esophagitis. The relative risk of oral leukoplakia was highest (11.5) among men who smoke and use nass quid. The relative risk was also elevated for persons who only use nass quid (5.6) or who only smoke cigarettes (7.8). Nass use had no effect on the risk of esophagitis. A slight elevation of risk (1.9) of esophagitis was observed for current smokers and drinkers. Of the men from whom blood was drawn for analysis, 4%, 66%, and 86% had low levels of retinol, carotene, and riboflavin, respectively. The high prevalence of oral and esophageal precancerous conditions and low blood levels of riboflavin, carotene, and vitamin A observed in the surveyed population, as well as the existing evidence on the possible protective effect of these nutrients in carcinogenesis, provide an opportunity and a justification for the chemopreventive trial, with the regression of observed precancerous lesions as the end point of the study.