[MOL] Risk Factors for Esophagus Cancer [01930] Medicine On Line


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[MOL] Risk Factors for Esophagus Cancer



Esophagus


Linda Morris Brown, M.P.H.*

Esophageal cancer is a malignancy that is well known for its marked variation by geographic area, ethnic group, and sex (Day and Munoz, 1982). In the United States, esophageal cancer accounts for only 1 percent of all cancers. However, this figure rises to almost 3 percent in black males (Ries et al., 1994). Annual U.S. incidence rates among blacks (17.1 per 100,000 males, 4.7 per 100,000 females) are more than three times those of whites (5.5 per 100,000 males, 1.7 per 100,000 females), and rates among males are more than three times those of females. The 5-year relative survival is poor--10 percent for whites and 6 percent for blacks (Ries et al., 1994). While the majority of esophageal cancers in the United States are squamous cell carcinomas, the incidence of adenocarcinomas appears to be rising, especially among white men (Blot et al., 1991). In 1987, adenocarcinomas accounted for 34 percent of all esophageal cancers in white men, 12 percent in white women, but only 3 percent and 1 percent, respectively, in black men and women (Blot et al., 1991). Many of the adenocarcinomas tend to arise from a medical condition known as Barrett's esophagus (Williamson et al., 1991).

International differences in esophageal cancer incidence as published in Volume VI of Cancer Incidence in Five Continents (Parkin et al., 1992) are striking. World standardized rates among males are highest in Calvados, France (26.5 per 100,000), and lowest in Israeli Jews (0.6 per 100,000). Rates among females range from 0.1 per 100,000 among Los Angeles Japanese to 8.8 per 100,000 in Bangalore, India. Rates for U.S. blacks rank among the highest in the world, while those for U.S. whites rank among the lowest. Internationally, the male/female rate ratio varies from less than two to more than 20.

In Western countries, 80 to 90 percent of the risk of squamous cell carcinoma of the esophagus can be attributed to consumption of alcohol and tobacco (Day and Munoz, 1982; Schottenfeld, 1984). Alcohol and tobacco appear to act independently, with the importance of each factor depending on the population under study (Tuyns, 1983). In a population of heavy drinkers, the major factor appears to be alcohol (Tuyns, 1983; Pottern et al., 1981), whereas tobacco is likely to be the most important factor in a population of heavy smokers (Wynder and Bross, 1961). Although little is known about the epidemiology of adenocarcinoma of the esophagus, the roles of tobacco and alcohol appear to be less important than for squamous cell carcinoma and do not explain the rapid rise in incidence of this tumor. Increases in the prevalence of obesity, however, may explain at least a portion of the recent increase (Brown et al., 1995; Vaughan et al., 1995).

The type of alcoholic beverage associated with the greatest risk of esophageal cancer in the majority of the American studies was hard liquor (Pottern et al., 1981; Wynder and Bross, 1961; Brown et al., 1988; Yu et al., 1988); however, in a couple of studies beer consumption was found to be the major determinant of risk (Kaul et al., 1986; Graham et al., 1990). Consumption of moonshine or other home-brewed alcoholic beverages has also been associated with excess risk of esophageal cancer in populations where these beverages are commonly used (Brown et al., 1988; Tuyns et al., 1979; Martinez, 1969).

In most studies, the risk of developing cancer of the esophagus was significantly increased among tobacco users, regardless of whether cigarettes, cigars, or pipes were smoked (Brown et al., 1994b; Yu et al., 1988; Tuyns and Esteve, 1983). Subjects who had quit smoking for 10 or more years appeared to have significantly reduced risks compared to current smokers (Brown et al., 1988; Yu et al., 1988).

A number of studies have shown an association between esophageal cancer and low socioeconomic status, independent of smoking and drinking, which may be associated with an inadequate diet (Day and Munoz, 1982; Schottenfeld, 1984). Poor nutrition in general has been suspected to be a cause of esophageal cancer. In Iran (Cook-Mozaffari et al., 1979), the Soviet Union (Kolicheva, 1980), and China (Yang et al., 1984), esophageal cancer is endemic in regions with limited diets and impoverished agriculture. Consumption of very hot beverages and the attendant possible thermal injury to the esophagus have also been considered a potential risk factor for esophageal cancer in less developed countries (DeJong et al., 1974; Victora et al., 1987; Ghadirian, 1987).

Data based on experimental animal diet studies (Gabrial et al., 1982), correlation studies involving areas of high and low esophageal cancer incidence (Van Rensburg, 1981) and on environmental studies conducted in high-risk areas of China (Yang et al., 1984) have suggested that decreased levels of specific nutrients (carotene, ascorbic acid, riboflavin, niacin, thiamin, zinc, magnesium, and selenium) may play a role in the etiology of esophageal cancer. Case-control studies in the United States (Brown et al., 1988; Yu et al., 1988; Graham et al., 1990; Ziegler et al., 1981), Puerto Rico (Martinez, 1969), Iran (Cook-Mozaffari et al., 1979), France (Tuyns 1983; Tuyns et al., 1987) and Italy (Decarli et al., 1987) have demonstrated an association between reduced consumption of certain basic food groups, notably fruits and vegetables, and esophageal cancer. Many of these studies have also reported a protective effect of vitamin C.

Until recently, esophageal cancer was unusually common in women from the rural, northern areas of Sweden, many of whom also had the Plummer-Vinson syndrome, which is associated with vitamin and iron deficiencies (Larsson et al., 1975). Chronic use of alcohol has been associated with deficiencies in vitamins A, C, D, the B vitamins, zinc, and protein (Broitman, 1983). Smoking may also contribute to vitamin C deficiencies (Kallner, 1981).

In the United States, use of tobacco and alcohol accounts for the majority of esophageal cancers, with nutritional factors also playing a role. Racial differences in susceptibility to the carcinogenic effects of alcohol and tobacco may explain, in part, the excess of squamous cell esophageal cancer in blacks compared to whites (Brown et al., 1994b).

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