Role of diet, alcohol and tobacco in oesophageal cancer, as illustrated by two contrasting high-incidence areas in the North of Iran and West of France

Risk factors for oesophageal, lung, oral and laryngeal cancers in black South Africans

The authors used data collected from 1995 to 1999, from an on-going cancer case-control study in greater Johannesburg, to estimate the importance of tobacco and alcohol consumption and other suspected risk factors with respect to cancer of the oesophagus (267 men and 138 women), lung (105 men and 41 women), oral cavity (87 men and 37 women), and larynx (51 men). Cancers not associated with tobacco or alcohol consumption were used as controls (804 men and 1370 women). Tobacco smoking was found to be the major risk factor for all of these cancers with odds ratios ranging from 2.6 (95% CI 1.5-4.5) for oesophageal cancer in female ex-smokers to 50.9 (95% CI 12.6-204.6) for lung cancer in women, and 23.9 (95% CI 9.5-60.3) for lung cancer and 23.6 (95% CI 4.6-121.2) for laryngeal cancer in men who smoked 15 or more grams of tobacco a day. This is the first time an association between smoking and oral and laryngeal cancers has been shown in sub-Saharan Africa. Long-term residence in the Transkei region in the southeast of the country continues to be a risk factor for oesophageal cancer, especially in women (odds ratio=14.7, 95% CI 4.7-46.0), possibly due to nutritional factors. There was a slight increase in lung cancer (odds ratio=2.9, 95% CI 1.1-7.5) in men working in 'potentially noxious' industries. 'Frequent' alcohol consumption, on its own, caused a marginally elevated risk for oesophageal cancer (odds ratio=1.7, 95% CI 1.0-2.9, for women and odds ratio=1.8, 95% CI 1.2-2.8, for men). The risks for oesophageal cancer in relation to alcohol consumption increased significantly in male and female smokers (odds ratio=4.7, 95% CI=2.8-7.9 in males and odds ratio=4.8, 95% CI 3.2-6.1 in females). The above results are broadly in line with international findings.

Dietary fat and salivary prostaglandin E2

A study of the relation between dietary fat intake and salivary prostaglandin E2 was undertaken in Transkei, South Africa. Samples of saliva were obtained from (1) Transkeians on a very low fat diet, (2) Transkeians on a low fat diet, (3) Transkeians on a medium fat diet, (4) British patients. Salivary PGE2 means for the groups were (1) 2357 pg/ml, (2) 2020 pg/ml, (3) 733 pg/ml, (4) 312.5 pg/ml. Differences between groups 1 and 3, 1 and 4, and 2 and 4 were significant. Rural Transkeians on a low-fat diet have an elevated level of PGE2 in saliva. As fat increases in the diet, PGE2 in saliva tends towards the level found in those who eat a western diet. An increase in the level of PGE2 production in the upper gastrointestinal tract and in the tissues of the body may be a factor in promoting cancer of the esophagus and diseases favored by Th1 immune dysfunction.

Alcohol and breast cancer. Where are we now and where do we go from here?

The alcohol-breast cancer hypothesis is important because (1) breast cancer is a major source of morbidity and mortality, (2) alcohol consumption is common, and (3) drinking is modifiable. Reports from more than 50 epidemiologic investigations of this hypothesis have now appeared. A recent metaanalysis of these studies indicates both a modest positive association between alcohol and breast cancer (an approximately 25% increase in risk with daily intake of the equivalent of two drinks) and a dose-response relation. Data suggest that risk increases with consumption of alcohol in general, regardless of beverage type. Several factors, including age, weight, and estrogen usage, have been shown to modify this relation in some studies. The authors discuss a series of methodologic issues in the study of alcohol and breast cancer. These include error in alcohol assessment, difficulties in evaluating small relative risks, and the potential for confounding. Several biologic mechanisms could account for an alcohol-breast cancer relation, with increasing attention being paid to a possible mediating effect of reproductive steroid hormones. Animal studies are a relatively recent development in this area; results have been mixed. Incorporation of more refined temporal, quantitative, and qualitative indicators of alcohol exposure in future epidemiologic studies would be valuable, as would further exploration of the endocrine and other metabolic effects of moderate alcohol consumption. The alcohol-breast cancer hypothesis remains intriguing, but causality has not been established.

A case-control study of diet and social factors in cancer of the esophagus in Transkei

A study of 100 patients with cancer of the esophagus and 100 controls matched for sex, age, and educational level was done in Transkei, with extensive inquiries into diet and social habits. The significant risk factors found were use of Solanum nigrum as a food (relative risk, 3.6), smoking (relative risk, 2.6), and use of traditional medicines (relative risk, 2.1). Consumption of traditional beer was not a risk factor.

Natural history and significance of esophageal squamous cell dysplasia

Balloon-mesh cytologic screening for esophageal cancer done in 255 asymptomatic high-risk United States veterans (age greater than 40 years, ethanol abuse for greater than 20 years, and cigarette smoking greater than 20 pack years) identified 37 patients with squamous cell dysplasia. Of the 37 patients with dysplasia, 28 were re-evaluated prospectively at 6-month intervals for up to 36 months by balloon-mesh cytology, esophagoscopy with vital staining and biopsies, chest radiographs, oropharyngeal examination, and indirect laryngoscopy. During prospective follow-up evaluation, cytology specimens were repetitively normal in 16 patients (57%), showed inflammatory changes in eight patients (29%), persisted as dysplasia in two patients (7%) (both had endoscopic and histologic evidence of esophagitis), and progressed to carcinoma in two patients (7%) (one esophageal, one laryngeal). Although histologic findings concurred with the resolution of dysplasia, biopsy specimens were characterized by a similar difficulty in distinguishing dysplasia from inflammation. Erroneous histologic diagnoses of carcinoma in situ were made in two patients with reflux esophagitis evident endoscopically and confirmed during the course of a 24-36 month follow-up period. The authors conclude that squamous cell dysplasia detected by balloon-mesh cytology is seldom a precursor of esophageal cancer in the high-risk U.S. population but, rather, is often related to esophagitis. Thus, balloon-mesh cytology has limited use as a screening method for the early detection of esophageal cancer in the United States.

Water contamination and esophageal cancer at Gassim Region, Saudi Arabia

Between January 1980 and December 1982, 183 patients with histologically confirmed carcinoma of the esophagus who were referred to a tertiary referral hospital were studied. Thirty-two (17%) patients were referred from Gassim Region at the north central part of Saudi Arabia. In contrast, only 5% of total cancer patient referrals were from this area. A case-control study showed a significant regional difference within Saudi Arabia and the most referrals from Gassim area. A prospective case-control study showed persistently high numbers of referrals from that region during 1983-1987. When patients from Gassim Region were compared with those referred from other locations, no statistical differences were noted between the two groups except for the source of drinking water. Water analysis from Gassim area showed a high solid content with elevated levels of calcium, magnesium, and to a lesser extent, chromium iron, cadmium, and cobalt. Traces of petroleum oil were found in five of six water samples from Gassim during 1983, compared with 3 of 49 samples from other areas. Mutagenicity tests on water specimens form Gassim Region indicated the presence of possible carcinogens. It is being suggested that the high prevalence of esophageal cancer in this region may be related to contamination of water by impurities such as petroleum oils. Malnutrition, particularly vitamin A deficiency, as well as other factors may have promoted such malignancies.

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.

Cancer of the esophagus: a model of causation

Cancer of the esophagus has shown peculiar worldwide geographic clustering; it has also occurred in excess among individuals in lower socioeconomic census tracts of certain cities. These facts have prompted inquiry into its etiology. Emphasis has been given to environmental effects, particularly mechanical and/or irritating processes, dietary deficiency, and a variety of carcinogens. Immunological susceptibility has been considered, although only infrequently. Overall, primary genetic factors have received short shrift in epidemiological investigations of this disease. An hypothesis of stress related cancer in concert with genotypic susceptibility is presented.

Increasing frequency of esophageal cancer among black male veterans

Between the years of 1975 and 1979, the frequency of diagnosis of esophageal cancer has doubled at the Baltimore VA Medical Center due to a rapid increase of esophageal cancer among black males. This increase was not related to increased yearly hospital admission rates, percentage of black patients admitted yearly, or increased use of the hospital for chronic disease processes. Detailed chart review and comparison with consecutive medical admissions as controls revealed heavy alcohol use and urbanization to be risk factors experienced more frequently by black than white male veterans. A serious question needs to be quickly answered: Does the rise of esophageal cancer at the Baltimore VAMC reflect a rise among black males only in Baltimore or does it reflect a rise nationwide among black males with a history of previous employment in the armed forces?

Nutritional status of African populations predisposed to esophageal cancer

Nutritional status indicators were assessed chemically in blood and urine taken from 625 Transkeians drawn from three age-groups in each of two regions: one with a moderate risk for esophageal cancer and one with a very high risk. Aggregate mean values for protein, albumin, vitamin A, and phosphorus were generally acceptable, but many subjects had inadequate (though not necessarily deficient) values for nicotinic acid (74% of subjects), magnesium (60%), vitamin C (55%), carotene (53%), riboflavin (41%), calcium (35%), and zinc (27%). Groups at highest risk for esophageal cancer had markedly lower serum magnesium and carotene concentrations and mildly depressed hemoglobin and hematocrit values, but such findings are not necessarily associated with esophageal cancer etiology. Possible intestinal malabsorption in the populations at highest risk may be associated with the unusually high fiber and phytate intake of the high-risk populations as well as with exposure to necrotizing mycotoxins. Thus, while protein and energy nutriture seem generally adequate, both the high- and moderate-risk populations had high incidences of multiple micronutrient malnutrition.