Risk factors for lung cancer in Singapore Chinese, a population with high female incidence rates

Dietary vitamins A and C and lung cancer risk in Louisiana

The authors describe the results of a hospital-based incident case-control study of lung cancer conducted in a high-risk region of southern Louisiana from January 1979 through April 1982. Dietary intake of carotene, retinol, and vitamin C was estimated from food frequency questionnaires administered to 1253 cases and 1274 controls. An inverse association was found between level of carotene intake and lung cancer risk, and this protective effect was specific for squamous and small cell carcinoma (odds ratio [OR] = 0.84, 95% confidence interval: 0.64-1.09, high intake). A stronger protective effect for these tumors was associated with dietary vitamin C intake (OR = 0.65, 0.50-0.87, high intake). A significant inverse gradient in risk with retinol intake was limited to adenocarcinoma (OR = 0.64, 0.44-0.94, high intake) and more pronounced among blacks.

Recent trends in cancer incidence among Singapore Chinese

Since the inception of cancer registration in Singapore in 1968, the incidence rates of malignancies have been monitored among the 3 major ethnic groups--Chinese (77% of population), Malays (15%) and Indians (6%). Substantial changes in incidence at various sites were observed in the period 1968-1982, which seem to represent a shift from the pattern of cancer incidence in China towards that prevailing in the West. We now report on the Singapore Chinese experience, in which the following changes were notable: decreases in rates of cancers of the stomach and oesophagus and increases in rates of cancers of the lung, colon, rectum, skin (excluding melanoma), breast and ovary. For several sites, the secular changes differed among age groups; among women under 50 years of age breast cancer increased particularly sharply and lung cancer decreased. Environmental and personal factors, potentially responsible for the change, are discussed.

Comparative histopathology of resected bronchial cancers of women in Hong Kong and Japan

Pathological findings relating to lung cancers removed surgically from women at the Kowloon Hospital (KH), Hong Kong, and the Cancer Institute Hospital (CIH), Japan (77 and 54 cases respectively), were examined in order to clarify possible differences between Hong Kong Chinese and Tokyo Japanese women. Adenocarcinoma was the most frequent subtype encountered in both hospitals, but the rate was higher in CIH (90.9% in CIH and 68.8% in KH); that of large-cell carcinoma was second in KH where the rate was higher (14.3% in KH and 0%, in CIH). A remarkable difference was observed in the location of adenocarcinomas; the percentages of central and peripheral types were 60.4% and 24.5% respectively in KH, but 4% and 96% respectively in CIH. The proportion of the central type (45.5%) was higher than that of the peripheral type (27.3%) in large-cell carcinomas of KH. The number of adenocarcinomas having a bronchiolo-alveolar pattern (which is observed more frequently in peripheral-type adenocarcinomas) was higher in CIH (50%) than in KH (17%). Tall columnar cells were observed more often in KH (43.1% in KH and 20.8% in CIH), and hobnail and cuboidal cells more often in CIH (31.4 and 80.4% respectively in KH, and 54.2 and 95.8% respectively in CIH). The difference may be explained by the frequent presence of tall columnar cells in the glands of central carcinomas, and hobnail and cuboidal cells in peripheral adenocarcinomas. The frequent occurrence of the central type of adenocarcinoma and large-cell carcinoma appears characteristic of the lung carcinomas removed from women in Hong Kong. This suggests the existence of exogenous causative agents for lung cancer in Hong Kong females.

Serum beta-carotene and subsequent risk of cancer: results from the BUPA Study

In the BUPA Study, a prospective study of 22,000 men attending a screening centre in London, serum samples were collected and stored. The concentration of beta-carotene was measured in the stored serum samples from 271 men who were subsequently notified as having cancer and from 533 unaffected controls, matched for age, smoking history and duration of storage of the serum samples. The mean beta-carotene level of the cancer subjects was significantly lower than that of their matched controls (198 and 221 micrograms l-1 respectively, P = 0.007). The difference was apparent in subjects from whom blood was collected several years before the diagnosis of the cancer, indicating that the low beta-carotene levels in the cancer subjects were unlikely to have been simply a consequence of pre-clinical disease. Men in the top two quintiles of serum beta-carotene had only about 60% of the risk of developing cancer compared with men in the bottom quintile. The study was not large enough to be able to indicate with confidence the sites of cancer for which the inverse association between serum beta-carotene and risk of cancer applied, though the association was strongest for lung cancer. The association may be due to beta-carotene affecting the risk directly or it may reflect an indirect association of cancer risk with some other component of vegetables or with a nonvegetable component of diet that is itself related to vegetable consumption.

Mortality among German vegetarians: first results after five years of follow-up

A prospective study of vegetarians recruited from all regions of the Federal Republic of Germany, including West Berlin, was started in 1978 after a preparatory phase of two years in which the cohort was established. The mortality of the 1,904 study participants was evaluated after a follow-up of five years, comparing observed deaths with expected rates based on the national mortality statistics. Of the 858 men and 1,046 women, 89% had followed their diet for at least five years at study entry, the majority of them as strict vegetarians (1,163). By the end of 1983, only 82 persons had died, whereas 219 deaths were expected. In both sexes, the mortality was lowest from cardiovascular diseases [standardized mortality ratio (SMR) for ischemic heart disease about 20] and from cancer (SMR 58 for men, 54 for women). Deaths from diseases of the respiratory and digestive system were also reduced. For individual cancer sites the observed numbers were extremely small, but the risk of dying from lung cancer was significantly reduced; however, deaths from cancers of the colon and rectum, prostate, and breast were rare or even absent. More deaths than expected were observed from stomach, pancreatic, testicular, and brain cancers. An internal comparison of mortality between strict and moderate vegetarians (741) suggests a higher mortality from all causes and malignant neoplasms among strict vegetarians in both sexes, although not statistically significant, and a lower mortality from circulatory system diseases for males. The possible influence of selection factors (e.g., "healthy participant effect," socioeconomic level, and body weight) on the findings of a decreased mortality is discussed together with the role of diet.

Dietary habits and lung cancer risk among Chinese females in Hong Kong who never smoked

This describes a retrospective study in which 88 lung cancer patients and 137 district-matched controls were interviewed concerning the effects of diet on lung cancer risk among Hong Kong Chinese women who never smoked tobacco. Those in the lowest tertile of consuming fresh fruit or fresh fish had statistically significant adjusted relative risks (RRs) of 2.4 and 2.8, respectively. The protective effects of diet, i.e., higher consumption of leafy green vegetables, carrots, tofu, fresh fruit, and fresh fish, were confined mostly to those with adenocarcinoma or large cell tumors. Only fresh fruit was found to positively, and smoked meats to negatively, affect the risk of squamous or small cell tumors. Foods high in vitamin C, retinol, and calcium seemed to exert larger effects. Subjects from larger households were shown to be more frequent consumers of fresh vegetables, fruit, and fish. Because the lifetime weighted household size could be used as a surrogate index of past dietary quality, when it was combined with current dietary intakes of fresh fruit, the RR increased as either factor decreased in a dose-response manner. The adjusted RR was 5.8 at the lowest level. Further testing of the validity of the lifetime weighted household size as an index of past dietary quality is needed.

Lung cancer among Chinese women

A case-control study involving interviews with 672 female lung cancer patients and 735 population-based controls was conducted to investigate the high rates of lung cancer, notably adenocarcinoma, among women in Shanghai. Cigarette smoking was a strong risk factor, but accounted for only about one-fourth of all newly diagnosed cases of lung cancer. Most patients, particularly with adenocarcinoma, were life-long non-smokers. The risks of lung cancer were higher among women reporting tuberculosis and other pre-existing lung diseases. Hormonal factors were suggested by an increased risk associated with late menopause and by a gradient in the risk of adenocarcinoma with decreasing menstrual cycle length, with a 3-fold excess among women who had shorter cycles. Perhaps most intriguing were associations found between lung cancer and measures of exposure to cooking oil vapors. Risks increased with the numbers of meals cooked by either stir frying, deep frying or boiling; with the frequency of smokiness during cooking; and with the frequency of eye irritation during cooking. Use of rapeseed oil, whose volatiles following high-temperature cooking may be mutagenic, was also reported more often by the cancer patients. The findings thus confirm that factors other than smoking are responsible for the high risk of lung cancer among Chinese women and provide clues for further research, including the assessment of cooking practices.

Concordance of histological classification of lung cancer with special reference to adenocarcinoma in Osaka, Japan, and the North-West Region of England

In routinely collected data adenocarcinoma of the lung appeared to be 3 times more frequent in Osaka, Japan, than in the North-Western (NW) Region of England (Manchester). Before embarking on comparative epidemiological studies, it was decided to investigate the comparability of histological diagnosis. Specimens from 60 NW Region lung cancer patients and 52 Osaka patients were exchanged and reviewed. The entire material was then independently assessed by the WHO Collaborating Centre for Histological Classification of Tumours. The interpretation of the WHO Classification (WHO, 1981) by the NW Region and by Osaka was upheld by the WHO Collaborating Centre in 89% and 93% of all cases and in 97% and 100% of adenocarcinoma cases respectively. Agreement between the 2 centres was 88% for the main cell types. Differences in the frequency of adenocarcinoma of lung between the NW Region and Osaka are thus not due to diagnostic artefact and require further exploration. The aetiological implications of the finding that many Chinese and Japanese women with lung adenocarcinoma do not smoke (77% in Osaka) are discussed.

Legume carotenoids

In recent years, the results of research studies have suggested a positive beneficial relationship between a vegetarian-based diet and low incidence of diseases, including coronary heart disease, cancer, obesity, dental caries, and osteoporosis. beta-Carotene has specifically been suggested as a nutrient with antitumorigenic properties. In this regard there is a need to evaluate the carotenoid content of foods. Legumes are one of the staple components of a vegetarian diet. This review specifically surveys the prevalence of carotenoids in food and forage legumes. In addition, the methods available for carotenoid analysis are discussed; factors affecting the determination of carotenoid content during maturation, germination, processing and storage are identified; research areas which have been inadequately explored are identified; and suggestions are made for future lines of investigation.

Vitamin A and female lung cancer: a case-control study on plasma and diet

Plasma and dietary levels of retinol and beta-carotene were evaluated in a consecutive series of 47 females with histologically proven primary lung cancer and 159 nonneoplastic hospital controls. The dietary questionnaire included 69 different items: special care was given to foods rich in vitamin A and seasonal foods (e.g., vegetables and fruits), whereas serum analysis was focused on retinol and beta-carotene. Age-adjusted mean values for cases and controls were, respectively, 458.3 vs. 551.3 mg for plasma retinol, 276.1 vs. 390.1 mg for plasma carotene; 598.1 vs 820.6 mg for daily retinol, and 628.0 vs. 882.5 mg for dietary carotene. The odds ratios for low vs. high tertile, adjusted for age, smoking, retinol or carotene, cholesterol, and triglycerides by multivariate analysis were, respectively, 1.13 for plasma retinol, 5.04 for plasma carotene, 3.27 for dietary retinol, and 2.93 for dietary carotene. For all the examined items, there was a trend of increased risk for the second and third tertile, and statistical significance was reached for plasma beta-carotene (p less than 0.05). The hypothesis that a higher risk of lung cancer is related to a low vitamin A consumption is supported by these data.

Dietary vitamin A and lung cancer: results of a case-control study among chemical workers

A nested case-control study conducted among a cohort of chemical manufacturing employees provided an opportunity to test the hypothesis that lung cancer risk is inversely related to dietary intake of vitamin A. Eligible for study were 308 former male employees who had died of lung cancer between 1940 and 1980. Two control groups, one a decedent and the other a "living" series, were individually matched to the cases one-for-one. Interviews were completed with 734 subjects or their next-of-kin and included a food frequency list. A vitamin A index was developed for each subject based on the frequency of consumption of 29 food items. After adjustment for a number of potentially confounding variables (e.g., smoking, educational level, and use of vitamin supplements), there was evidence that vitamin A intake was inversely associated with lung cancer risk. The effect was most pronounced in the comparisons with the "living" controls and appeared strongest among cigarette smokers. Subjects in the lowest tertile of vitamin A intake had approximately twice the risk of lung cancer as those in the highest. Analyses of an index of carotenoids and of individual food items suggested that plant sources of vitamin A may play a more important role in producing the effect than do animal sources.

Interaction of drugs and retinol

In liver microsomes of ethanol-fed rats, retinol competitively inhibited the hydroxylation of aniline, the demethylation of dimethylnitrosamine, and the oxidation of ethanol to acetaldehyde, whereas the inhibition of benzphetamine demethylation was of the mixed type in microsomes of phenobarbital-treated, ethanol-treated or control rats. Conversely, benzphetamine exerted a striking inhibition of the 4-hydroxylation of retinol in microsomes of phenobarbital-treated rats. At the concentration used, ethanol (100 mM) and dimethylnitrosamine (10 mM) had no such effect. In vivo administration of phenobarbital resulted in a 9-fold increase in the Vmax of the microsomal retinol 4-hydroxylase activity, with a 3-fold increase of the Km, whereas ethanol feeding resulted in a doubling of the Vmax with no significant change in the Km. The induction of this microsomal retinol-metabolizing system may contribute to the hepatic vitamin A depletion that has been reported previously after either ethanol or drug administration. Conversely, the observed inhibition, by retinol, of microsomal drug metabolism, including the demethylation of dimethylnitrosamine, may be of significance with regards to the interaction of retinol with carcinogenesis.

Vitamin A, carotenoids, and retinoids

One promising area of current research in chemoprevention is the possibility that micronutrients, including vitamin A analogues, may decrease cancer incidence. The term "vitamin A" refers either to retinol (preformed vitamin A) and its synthetic analogues, or to certain carotenoids (provitamin A), which are converted to retinol in the body, as needed. Retinol and the other retinoids are integrally involved in cell growth and differentiation, which may affect carcinogenesis. Such a role has been supported by a large number of in vitro and animal experiments. Data from studies among humans are sparse, in part because most dietary studies have been conducted in populations in which the vast majority of vitamin A intake is actually beta-carotene and other carotenoids, found in carrots and other vegetables and fruits. Although the carotenoids do not have the hormone-like properties of retinol, they do have a potent antioxidant effect and could thus reduce cancer risk by preventing tissue damage due to oxidation. This possibility is supported by data from a large number of observational epidemiologic studies, most of which have consistently found an inverse relation between consumption of carotene-rich vegetables and cancer risk. However, the only direct way to determine whether carotenoids have a beneficial effect is through large, carefully conducted randomized trials. Several such studies are currently underway and should provide sound evidence on which future medical policy and practice can be based.

No association between HLA antigens and adenocarcinoma of the lung in non-smoking Chinese women in Hong Kong

A high incidence rate of lung cancer with preponderance of adenocarcinoma in non-smokers has been reported in women of southern Chinese ethnic origin. Thirty-three southern Chinese female patients with primary adenocarcinoma of the lung, all lifelong non-smokers, were typed for HLA-A and B antigens to study the possibility of genetically determined susceptibility factors. The antigen frequencies were compared with those of 110 healthy controls. No significant difference in antigen frequencies was found in the patients compared with controls. Studies on other possible factors determining susceptibility to lung cancer in Chinese women are necessary.

Beta-carotene therapy for erythropoietic protoporphyria and other photosensitivity diseases

This paper describes the development of the use of carotenoid pigments in the treatment of light-sensitive skin diseases. It also discusses the animal and human studies involved in determining whether carotenoids have any anti-cancer activity. The possible mechanisms of carotenoid photoprotective and anti-cancer actions are briefly discussed.

Epidemiologic studies of vitamins and cancer of the lung, esophagus, and cervix

Epidemiologic studies of the relationships between vitamins and 3 types of cancer are reviewed. First, the widely reported association between vitamin A and beta-carotene and risk of lung cancer is considered. In a large population-based case-control study of lung cancer among white males in New Jersey, increased intake of vegetables, dark green vegetables, dark yellow-orange vegetables, and carotenoids were each associated with reduced risk, but intake of retinol or total vitamin A was not related. The protective effect of vegetables was limited to current and recent cigarette smokers, which suggests that vegetable intake prevents a late-stage event in carcinogenesis. Consumption of dark yellow-orange vegetables was consistently more predictive of reduced risk than either the total carotenoid index or consumption of any other food group, possible because of the high content of beta-carotene in this food group. The results and limitations of other epidemiologic studies of diet and lung cancer are reviewed. Second, the evolving relationship between multiple micronutrient deficiencies and esophageal cancer is discussed. In a death certificate-based case-control study of esophageal cancer in black males in Washington, D.C., several indicators of general nutritional status, including consumption of fresh or frozen meat and fish, dairy products and eggs, and fruit and vegetables, and the number of meals eaten per day, were inversely and independently correlated with the risk of esophageal cancer. Estimates of intake of micronutrients, such as carotenoids, vitamin C, thiamin, and riboflavin, were less strongly associated with reduced risk than were the broad food groups that provide most of each micronutrient. Thus no single micronutrient deficiency was identified. Other studies suggest that generally poor nutrition may partially explain the susceptibility of urban black men to esophageal cancer. Finally, the postulated association between low folacin levels and risk of cervical cancer is examined. Among women who use oral contraceptives, serum and red blood cell folacin levels were reported to be lower among those with cervical dysplasia. In a clinical trial involving oral contraceptive users, cervical dysplasia gradually decreased in the group supplemented with oral folate but remained unchanged in the group given the placebo. Other epidemiologic studies of diet and cervical cancer are discussed.

An analysis of some risk factors for lung cancer in Hong Kong

Lung cancer has been the major cause of cancer death in Hong Kong for more than a decade. Although it is known that some 95% of male cases can be attributed to smoking, the etiological factors in women remain elusive. Among "never-smoked" female cases, increases in attributable risk from passive smoking were limited to only some of the histological types of lung carcinomas, and an overall analysis of all types did not reveal any significant increase in relative risk from this source. Other environmental factors which encourage bronchial irritation are suspected. Methodological differences may explain the differences in proportional distributions of histological lung tumor types noted between previous reports, and the risk values attributed therein to active and passive smoking.

Vitamin A and lung cancer: a perspective

Sixteen studies of the relationship between lung cancer and vitamin A in humans are critically reviewed: eight dietary studies and eight serum studies. Of the eight dietary studies, only five had case samples large enough to warrant meaningful statistical analysis. Three dietary studies reported a negative association between vitamin A intake and lung cancer after proper adjustment for cigarette smoking and socioeconomic effects; the results suggested that daily consumption of green-yellow vegetables reduces the risk of lung cancer in all categories of smokers. The reduction in risk was found to be greatest in persons in the higher socioeconomic strata. Four dietary studies suggested that high intake of dietary vitamin A has a protective effect against the development of squamous and small cell carcinoma of the lung in smokers. Three studies revealed a lower risk of lung cancer among persons who consume carrots and milk daily. None of the eight serum studies reviewed had large enough samples of lung cancer cases to allow for meaningful statistical analysis. However, four of the serum studies reported significantly lower serum vitamin A levels in lung cancer cases than in controls. Analysis of the above studies demonstrated shortcomings in each. Future studies should include all of the following factors: more complete vitamin A indices, examination of the histological type of lung cancer, a large enough pool of both male and female patients for statistical analysis, and proper adjustment for the effects of age, sex, smoking, and socioeconomic status.

Nutrition and prostate cancer: a case-control study

This one-to-one, age- and race-matched case-control study involved 181 histologically confirmed black prostate cancer patients and 181 controls seen at three major hospitals in Washington, DC, during the period 1979-1982. Personal interviews were conducted to obtain the number of times food items of specified serving size were consumed per week by cases and controls during the age periods 30-49 and 50 years and older. Then the average daily consumption of each of 18 nutrients per 1,000 calories was calculated. There was risk enhancement associated with increased intake of proteins, total fat, saturated fat, oleic acid, and vitamin A during the age period 30-49 years. The association was highly significant for vitamin A and approached statistical significance for the other four nutrients. A hypothesis based on disturbance of the zinc-retinol binding protein-vitamin A axis was put forward to explain the relative risk enhancement effect of vitamin A on prostate cancer.

Lung cancer in Hong Kong Chinese: mortality and histological types, 1973-1982

The histological types of lung cancer in Hong Kong Chinese in both sexes are presented. When the 1981 WHO Classification is used instead of the 1967 WHO Classification, more than half of the large cell carcinoma is retyped into the adenocarcinoma group. The proportion of large cell carcinoma thus decreases from 14.7% to 6.9% in the male and from 10.0% to 4.4% in the female. Compared to the 1948-1962 report from the same Department, there is a shift of the peak age distribution from the 6th decade to the 7th decade. Compared to the 1960-1972 report from the same Department, there is a significant increase in the relative frequency of adenocarcinoma in both sexes, from 15.6% to 25.8% in the male and 34.3% to 49.6% in the female. Adenocarcinoma continues to be the most common histological type in females and it is becoming the commonest type in males. It is also found in the present series that in the male, the proportion of adenocarcinoma decreases with increasing age, from 60% in the third decade to 26.6% in the eighth decade. In spite of the high female lung cancer mortality rate and therefore low male:female ratio of about 2:1, there is a tendency for this ratio to increase over the years. It is speculated that factors other than active cigarette smoking may be responsible for the peculiar and changing histological pattern and the female predominance in lung cancer in Hong Kong Chinese.

Relation of serum vitamins A and E and carotenoids to the risk of cancer

Epidemiologic studies suggest that low carotene intake and low levels of serum retinol may be associated with an increased risk of cancer. Likewise, in some animal studies vitamin E has been associated with a reduced rate of induced cancers. Therefore, we measured retinol, retinol-binding protein, vitamin E (alpha-tocopherol), and total carotenoids in serum collected in 1973 from 111 participants in the Hypertension Detection and Follow-up Program who were free of cancer at the time but were diagnosed as having cancer during the subsequent five years. These measurements were compared with those in 210 controls who were matched for age, sex, race, and time of blood collection, and who remained free of cancer. Mean values for retinol were similar for cases and controls (67.3 and 68.7 micrograms per deciliter, respectively [95 per cent confidence limits for case-control difference, -6.7 to 3.5]). Values were also similar for retinol-binding protein (6.01 and 5.94 mg per deciliter [-0.42 to 0.56]), and carotenoids (114.5 and 111.6 micrograms per deciliter [-9.1 to 15.9]). The mean base-line retinol level in the 18 subjects with subsequent lung cancer was higher than that in their matched controls (79.0 vs. 71.4 micrograms per deciliter, -4.9 to 19.7). Serum vitamin E levels were somewhat lower in subjects who later had cancer than in controls (1.16 and 1.26 mg per deciliter, -0.22 to 0.02), in part because of the confounding effect of serum cholesterol levels (when adjusted for lipid levels, the case-control difference was -0.05 mg per deciliter; -0.17 to 0.07). These data do not support hypotheses relating intake or serum levels of antioxidant vitamins to a reduced cancer risk.

Vitamin therapy in the absence of obvious deficiency. What is the evidence?

Vitamins are a group of organic compounds occurring naturally in food and are necessary for good health. Lack of a vitamin may lead to a specific deficiency syndrome, which may be primary (due to inadequate diet) or secondary (due to malabsorption or to increased metabolic need), and it is rational to use high-dose vitamin supplementation in situations where these clinical conditions exist. However, pharmacological doses of vitamins are claimed to be of value in a wide variety of conditions which have no, or only a superficial, resemblance to the classic vitamin deficiency syndromes. The enormous literature on which these claims are based consists mainly of uncontrolled clinical trials or anecdotal reports. Only a few studies have made use of the techniques of randomisation and double-blinding. Evidence from such studies reveals a beneficial therapeutic effect of vitamin E in intermittent claudication and fibrocystic breast disease and of vitamin C in pressure sores, but the use of vitamin A in acne vulgaris, vitamin E in angina pectoris, hyperlipidaemia and enhancement of athletic capacity, of vitamin C in advanced cancer, and niacin in schizophrenia has been rejected. Evidence is conflicting or inconclusive as to the use of vitamin C in the common cold, asthma and enhancement of athletic capacity, of pantothenic acid in osteoarthritis, and folic acid (folacin) in neural tube defects. Most of the vitamins have been reported to cause adverse effects when ingested in excessive doses. It is therefore worthwhile to consider the risk-benefit ratio before embarking upon the use of high-dose vitamin supplementation for disorders were proof of efficacy is lacking.

Epidemiologic studies on vitamin A and cancer

Data derived from epidemiologic studies on human populations are consistent with the protection from cancer afforded by vitamin A seen in animal studies. The populations studied are diverse, including groups living in India, Singapore, Norway, the United Kingdom, and the United States. The methodologies brought to bear on the question have been equally varied. Although there are inconsistencies in findings, and instances in which an association has not been observed, the weight of evidence suggests that the intake of vitamin A from dietary or other sources may inhibit the onset of lung cancer and possibly other cancers. However, the evidence from human populations is not experimental and it is conceivable that the associations observed are not causal. Additional epidemiologic research is needed to determine what sites of cancer may be inhibited by vitamin A and whether cancer growth at any other site is enhanced by high vitamin A intakes. It is also important that controlled trials using vitamin A as a chemopreventive agent be considered as a means of determining whether the epidemiologic findings are of clinical significance.

The distribution of selenium and cancer mortality in the continental United States

An hypothesis was proposed that selenium concentration in the environment, as measured by the uptake of this element by forage crops, exerted an apparent effect on cancer incidence, such that cancer mortality in the continental United States was lower where the selenium concentration was high than where the concentration was low. The purpose of the present study is to test this hypothesis for statistical significance and to discover whether the apparent pattern of cancer mortality in relation to selenium distribution holds true with respect to all ages. Two main types of statistical analyses were employed: analysis of variance and trend analysis, both applied to all age groups and both sexes. Data presented in this paper show that significant interactions exist between selenium distribution and sex in relation to deaths caused by cancer of the digestive organs, respiratory organs, and the breast. Geographic variations in selenium may be viewed as variations in the intake of this element in the diet. A significant interaction may thus suggest that the particular cancer in question has in its origin a dietary factor that includes some measure of selenium intake. A discussion involving contributions from various disciplines is presented to explain the significant results reported in this paper. This paper shows that a pattern exists between the geographical distribution of selenium using forage crops as a guide for dietary intake and cancer mortality (ICD 140-209,150-159,160-163, and 174) such that an inverse relationship exists between selenium concentration in an area and cancer mortality in the same area.

Clinical features of bronchogenic carcinoma in Hong Kong. Review of 480 patients

A retrospective study was made of 480 Chinese patients with proven bronchogenic carcinoma, the top cancer in Hong Kong. The male-to-female sex ratio was low (1.9:1) and the female mortality rate ranked amongst the world's highest. The four major histologic types accounted for 87% of the cases: 39% epidermoid, 12% small cell anaplastic, 29% adenocarcinoma, and 7% large cell anaplastic. History of smoking was associated with epidermoid and small cell anaplastic carcinoma only. The commonest symptoms were anorexia and malaise (67%) and cough (51%). Overall our patients presented late and only 30 (6%) had curative surgery. The relatively rare occurrence of deep vein thrombosis (0.7%) is in keeping with the known low incidence of venous thrombosis in Chinese. Adenocarcinoma was a distinct group characterized by its preponderance in females (43%), lack of association with smoking habit (61% female cases being nonsmokers), high frequency of neurologic manifestation (21%) and clinical, roentgenographic, and bronchoscopic features of a predominantly centrally situated tumor. Possible etiologic factors for the high and still increasing incidence of adenocarcinoma are discussed.

Dietary habits and lung cancer risk

A previously reported negative association between a high index of dietary vitamin A and lung cancer incidence was confirmed in an extended follow-up, covering 11 1/2 years, of 13,785 men and 2,928 women, Responses to a postal questionnaire provided the dietary information. Relationships between the major dietary items and lung cancer were explored for various diagnostic subsets of the 168 lung cancer cases diagnosed among the study subjects. Analyses were stratified for sex, age, residence characteristics, cigarette smoking and, at times, socioeconomic group. Although the data do not permit a firm interpretation in terms of risk enhancement by a marginal retinoid deficiency, we found that the apparent protection afforded by higher intakes of vitamin A or its provitamins was particularly strong for lung cancer appearing as squamous-cell carcinoma and among those with higher alcohol intakes. The individual food items which showed the strongest negative association with lung cancer were carrots and milk. These two items made a major contribution to the vitamin A index and its variation among the respondents.

Vitamin A: evidence for its preventive role in human cancer

Both the provitamin beta-carotene and natural vitamin A and its derivatives (the retinoids) are being proposed as potential chemopreventive agents. The biochemistry and pharmacology of vitamin A suggest a number of mechanisms whereby carcinogenesis can be affected. Epidemiologic studies have consistently demonstrated an increased relative risk of cancer for people with low vitamin A intake or low-to-normal serum retinol values. Chemoprevention trials in humans are only now beginning. In the interim, daily consumption of vitamin-A-containing foods may be a "prescription" worth following.

Sex differences in human mortality: the role of genetic factors

This paper reviews evidence concerning genetic factors that influence sex differences in human mortality, with attention to the interactions between genetic and environmental factors. Some widely quoted earlier conclusions, for example, that males have consistently higher fetal mortality than females, are not supported by current evidence. For example, for late fetal mortality, males had higher rates than females in earlier historical data, but not in recent data for several advanced industrial countries. This reflects a changing balance between an inherently greater female vulnerability for one major type of late fetal mortality and inherently greater male vulnerability for several other types of late fetal mortality that have declined in importance as health care has improved. Males appear to be inherently more vulnerable than females to infant mortality, although the causes of this vulnerability are poorly understood. X-linked immunoregulatory genes appear to contribute to greater female resistance to infectious diseases. Despite these apparent inherent advantages for females, in some situations females have had higher infant mortality and higher infectious disease mortality than males, apparently due to environmental disadvantages for females, such as less adequate diet and health care. Inherent sex differences in reproductive physiology and anatomy contribute to higher female mortality for breast cancer and maternal mortality. For these causes of death, as for the other categories discussed, the death rates and thus the contributions to sex differences in total mortality vary considerably depending on environmental conditions. Several hypothesized contributions of sex hormones to sex differences in mortality are at present controversial due to contradictions and limitations in the available data. There may be effects of male sex hormones on sex differences in behavior which contribute to males' higher death rates for accidents and other violent causes. Women's endogenous sex hormones may reduce women's risk of ischemic heart disease. For both violent deaths and ischemic heart disease it appears that any genetic contributions to sex differences in mortality are strongly reinforced by the cultural influences that foster more risky behavior in males, including more use of weapons, employment in hazardous occupations, heavy alcohol consumption and cigarette smoking. It appears that these cultural influences on sex differences in behavior are widespread cross-culturally in part because of the effects of inherent sex differences in reproductive functions on the cultural evolution of sex roles. These examples illustrate the complexity and importance of interactions between genetic and environmental factors in determining sex differences in human mortality.

The surgeon general's "epidemiologic criteria for causality." A critique

The methodology of the 1982 Report of the Surgeon General is examined with special reference to smoking and lung cancer. Part II of the Report describes the five criteria for causality that have guided the judgment of committees since 1964. I show that not one of the criteria, plausibly interpreted, is satisfied by the epidemiologic evidence for lung cancer. A weakness underlying all the Reports is a prior failure to recognize all the logical possibilities inherent in an association between smoking and a disease. The five criteria and the subjective method of "judgment" are inappropriate to a scientific analysis; they should be replaced by the objective testing of hypotheses. Limitations in the evidence and in concepts about tobacco carcinogenesis preclude definitive conclusions. Nevertheless, the entire association between cigarette smoking and lung cancer--at least in male Caucasoid populations--is unlikely to be explained by causation.

Lung cancer in Greenland--selected epidemiological, pathological, and clinical aspects

One hundred and seven cases of lung cancer were first diagnosed among indigenous Greenlanders during the 25 years from 1955 to 1979. Compared with the Danish population, relative risk of lung cancer among male Greenlanders increased from 0.4 in 1955-1959 to 1.1 in 1975-1979. Relative risk among women increased from 0.7 to 2.1. The age-adjusted rate for women during the period 1975-1979 is one of the highest on record. This increase in lung-cancer risk followed a sharp rise in the use of cigarettes in the general population. An association with cigarette consumption was also suggested by tumor histology and location. A synergistic role of other risk hazards is possible. Local factors arising from previous tuberculosis involvement may have favored lung cancer development in men. More than 2/3 of the cases of lung cancer diagnosed between 1955 and 1974 were brought to medical attention because of clinical symptoms although most of the population was screened annually or biannually for tuberculosis. Intervention through screening had little impact on the overall very low survival rate.

Cigarette smoking and lung cancer: a continuing controversy

During the late 1950s Sir Ronald Fisher questioned the already popular, but in his view precipitate, causal interpretation of the association between smoking and lung cancer. His pungently expressed views began a controversy that has smouldered and sometimes flared ever since. The most recent attack on Fisher's constitutional hypothesis was launched by Reif and in this paper I consider the validity of his criticisms. A range of evidence shows that it is not yet possible to distinguish between constitutional and causal-plus-constitutional interpretations although recent studies indicate that a pure causal hypothesis is incapable of explaining the full association as observed in Western populations. Unfortunately, errors of diagnosis and death certification still impede the rigorous testing of adequately formulated hypotheses.

Serum retinol and the inverse relationship between serum cholesterol and cancer

Several human studies have shown an inverse relation between vitamin A intake (and serum concentrations of retinol and carotene) and cancer. Serum cholesterol concentrations have also been reported in inverse relation to cancer. In a study of 3102 people in Evans County, Georgia, who were followed for over 12-14 years to assess the incidence of cancer there was an inverse association between the risk of cancer and both serum retinol and serum cholesterol concentrations. The data also showed an unexpectedly strong correlation between serum retinol and total cholesterol concentrations. The inverse relationship with cancer was stronger with serum retinol than with cholesterol, which suggested that the association with cholesterol might be secondary. This suggestion may also explain the cholesterol-cancer association reported in several other cohort studies. Further studies of the relation between serum concentrations of cholesterol, retinol, and carotene and the incidence of cancer are needed.

Dietary vitamin A and risk of cancer in the Western Electric study

Intake of dietary provitamin A (carotene) was inversely related to the 19-year incidence of lung cancer in a prospective epidemiological study of 1954 middle-aged men. The relative risks of lung cancer in the first (lowest) to fourth quartiles of the distribution of carotene intake were respectively, 7.0, 5.5, 3.0, and 1.0 for all men in the study, and 8.1, 5.6, 3.9, and 1.0 for men who had smoked cigarettes for 30 or more years. Intake of preformed vitamin A (retinol) and intake of other nutrients were not significantly related to the risk of lung cancer. Neither carotene nor retinol intake was significantly related to the risk of other carcinomas grouped together, although for men in whom epidermoid carcinomas of the head and neck subsequently developed, carotene intake tended to be below average. These results support the hypothesis that dietary beta-carotene decreased the risk of lung cancer. However, cigarette smoking also increases the risk of serious diseases other than lung cancer, and there is no evidence that dietary carotenoids affect these other risks in any way.

Can dietary beta-carotene materially reduce human cancer rates?

Human cancer risks are inversely correlated with (a) blood retinol and (b) dietary beta-carotene. Although retinol in the blood might well be truly protective, this would be of little immediate value without discovery of the important external determinants of blood retinol which (in developed countries) do not include dietary retinol or beta-carotene. If dietary beta-carotene is truly protective--which could be tested by controlled trials--there are a number of theoretical mechanisms whereby it might act, some of which do not directly involve its 'provitamin A' activity.

Differences in lung cancer risk from smoking among Japanese, Chinese and Hawaiian women in Hawaii

The age-adjusted lung cancer incidence rates among Japanese, Chinese and Hawaiian women in Hawaii do not correlate to their respective cigarette smoking exposures. We conducted a case-control study to determine the lung cancer risk associated with smoking among these three ethnic groups of women by reviewing the medical records of 176 Japanese, 67 Chinese and 132 Hawaiian lung cancer patients diagnosed from 1968 to 1978. Smoking histories, as well as socioeconomic indexes, for these cases were compared to those of 2,404 sex- and race-matched controls from the general population. Controlling for age and socioeconomic index, we found that lung cancer risk associated with smoking was greatest for Hawaiian (O.R.=10.5), less for Japanese (O.R.=4.9) and least for Chinese women (O.R.=1.8). While smoking was associated with a significant increase in lung cancer risk for all histologies among Japanese and Hawaiian woman, the risk was much greater for epidermoid and small-cell types than for adenocarcinoma. Among Chinese women, epidermoid and small-cell lung cancer were the only histologies showing a significant association with smoking. There was some suggestion that increased lung cancer risk was associated with a higher socioeconomic index after controlling for age and smoking, at least among Japanese born in Japan and Hawaiians with adenocarcinoma. The population risk for lung cancer attributable to smoking was found to be 79% for Hawaiian women, but only 44% for Japanese and merely 11% for Chinese women. Thus, we concluded that the majority of lung cancer occurring in Japanese and particularly Chinese women in Hawaii is due to factors other than cigarette smoking.

Diet and cancer of the esophagus

The reported dietary, alcohol consumption and smoking habits of 147 Roswell Park Memorial Institute white male patients diagnosed with cancer of the esophagus were compared with the reports of 264 white males of comparable ages with diagnoses other than cancer. Overall frequency of vegetable an fruit consumption was associated with lower risk; persons reporting fruit and/or vegetable consumption 31-40 times a month had significantly greater risk than those who reported consumption 81 times a month or more. Calculated indexes of vitamin A and vitamin C intake were similarly related to reduction in risk. Dose-response gradients were observed for frequency of vegetable and/or fruit consumption, as well as for vitamin A and C intake. The putative protective effect of vegetable and fruit intake remained evident after controlling for its possible association with smoking and drinking. Previously reported associations of smoking, alcohol use and social class, as measured by type of occupation, were replicated in these data. The findings of this investigation in instances of colon, lung, bladder, oral, and laryngeal cancers, and with evidence of tumor inhibition by vegetable properties in animals. Interpretation of the findings is limited by the difficulties of retrospective assessment of dietary intake and by possible confounding by other factors known to be related to esophageal cancer.