Biomedical subjects

A Schatzkin

Publications and source records attributed to A Schatzkin.

At least 19 recordsLinked to original sources

PubMed1992

Does cancer survival differ for older patients?

The relation of age to 5-year relative survival rates was examined for leading sites of cancer resulting in death among 127,554 patients; data from 1978 to 1982 were studied for four areas of the Surveillance, Epidemiology and End Results program of the National Cancer Institute. Overall and stage-stratified relative survival rates declined with advancing patient age for cancer of the lung, prostate, pancreas, bladder, oral cavity, uterus, cervix, ovary, and large bowel (women only). In men, this trend was not explained by age differences in stage of diagnosis, whereas, among women, age was associated with more advanced disease for most sites examined. Although overall survival rates were lower in black patients compared with white patients, the age-survival and age-stage trends were similar in the two racial groups.

Black or African American↗

PubMed1992

Sample size for studying intermediate endpoints within intervention trails or observational studies.

An intermediate endpoint is a biologic event or marker that is a precursor to a given health outcome. Examples of potential intermediate endpoints include serum cholesterol for coronary heart disease, endogenous steroid hormones for breast cancer, and CD4 count for acquired immunodeficiency syndrome. When one is studying a potential intermediate endpoint in the context of an intervention trial, five types of questions may be investigated: 1) Does the intervention affect the intermediate endpoint? 2) Is the intermediate endpoint associated with prognostic or risk factors? 3) Is the intermediate endpoint associated with the main outcome? 4) Is the intervention effect on the main outcome mediated by the intermediate endpoint? 5) Are the prognostic or risk factor effects mediated by the intermediate endpoint? In this paper, the authors show that each of these questions had different sample size requirements, and they illustrate their point with a discussion of an ancillary study of large bowel epithelial proliferation in the National Cancer Institute's Polyp Prevention Trial. The same methods may be used in an observational study, in which case questions 2, 3, and 5 are relevant. However, much larger numbers than those used in the Polyp Prevention Trial example will be required when the main outcome is rare.

Colonic Polyps↗

PubMed1992

Serum cholesterol level, body mass index, and the risk of colon cancer. The Framingham Study.

BACKGROUND: Some studies have linked low serum cholesterol levels to increased risk of colon cancer, particularly in men. Results have been inconsistent, with preclinical disease frequently offered to explain any apparent association. METHODS: The Framingham Study cohort of 5209 persons, initially 30-62 years of age and observed more than 30 years, was evaluated. Baseline data included lipoprotein fractions, total cholesterol levels, body mass index, alcohol intake, and cardiovascular risk variables such as cigarette smoking, hypertension, and glucose intolerance. RESULTS: In this population, colon cancer in men is related inversely to serum cholesterol levels, even when the first 10 years of follow-up are eliminated to reduce the effect of preclinical disease. This effect is concentrated in the Svedberg 0-20 fraction, corresponding to low-density lipoprotein levels. Another finding only in men is the direct relation of body mass index to colon cancer incidence. CONCLUSIONS: Combined initial low serum cholesterol levels and obesity appear to indicate a four times greater risk for colon cancer in men as compared with people with average values of both variables. The reasons for these observations are unknown.

Adult↗

PubMed1992

Statistical validation of intermediate endpoints for chronic diseases.

We discuss the implementation of a criterion due to Prentice for the statistical validation of intermediate endpoints for chronic disease. The criterion involves examining in a cohort or intervention study whether an exposure or intervention effect, adjusted for the intermediate endpoint, is reduced to zero. For example, to examine whether serum cholesterol level is an intermediate endpoint for coronary heart disease (CHD), we may investigate the effect of the cholesterol lowering drug cholestyramine on CHD incidence adjusted for serum cholesterol levels. We show that use of this criterion will usually demand some form of model selection. When the unadjusted exposure or treatment effect is less than four times its standard error, the analysis can usually lead only to a weak form of validation, a conclusion that the data are not inconsistent with the validation criterion. More significant unadjusted exposure effects offer the potential for stronger types of validation statement such as 'the intermediate endpoint explains at least 50 per cent (or 75 per cent) of the exposure effect'.

Biomarkers↗

PubMed1992

Statistical validation of intermediate markers of precancer for use as endpoints in chemoprevention trials.

Using an intermediate marker of precancer as an endpoint for evaluating agents that may prevent cancer involves a presumption that the modification of the marker will be accompanied by a modification of cancer incidence. This presumption can hold only if the marker is on or very closely linked to a causal pathway. Epidemiologists have discussed the nature of evidence required to infer causal relationships, and we briefly survey their work. Studies relating exposure (E) to marker (M) provide only indirect evidence for causality. Those relating marker (M) to disease (D) are more relevant. We propose a new validation criterion based on an analysis of the three-way relationship of exposure (E), marker (M) and disease (D). We discuss the level of evidence required for using intermediate markers as endpoints for Phase II and Phase III trials, and propose very stringent criteria for Phase III trials. For Phase II trials, we propose less stringent criteria, but still recommend that the marker (M) should have been shown to have a strong association with disease (D).

Anticarcinogenic Agents↗

PubMed1992

Plasma lipid and lipoprotein concentrations of men consuming a low-fat, high-fiber diet.

This study assessed the influence of a low-fat, high-fiber diet on blood lipid concentrations of 42 men with desirable or moderately elevated cholesterol concentrations. A low-fat diet (19% fat, 4% saturated fatty acids, 4.6 g fiber/MJ) was compared with a high-fat diet (41% fat, 15% saturated fatty acids, 2.0 g fiber/MJ) and with subjects' self-selected diets. Substituting the low-fat for the high-fat diet decreased total, low-density-lipoprotein, and high-density-lipoprotein cholesterol by 17-20%. Lipid changes between 6 and 10 wk were minor. A reduction in plasma cholesterol of greater than 0.52 mmol/L was achieved with the low-fat diet in 59% of men changing from their self-selected diets and in 79% changing from the high-fat diet. Percent reduction was independent of subjects' cholesterol classification. Results indicate that significant reductions in plasma cholesterol can be achieved by the majority of men committing to a low-fat, high-fiber diet.

Adult↗

PubMed1991

The cancer experience in the Framingham Heart Study cohort.

The almost 40-year records of The Framingham Heart Study (FHS) cohort were reviewed to establish the cancer experience of this noninstitutionalized group of white subjects. Diagnoses were confirmed from pathology and laboratory reports and clinical notes. Age-specific incidence rates were compared with Connecticut Surveillance, Epidemiology, and End Results (SEER) data. Among the 5209 subjects, 1201 malignancies were confirmed. Median age at diagnosis was 69 for men and 65 for women. Lung, prostate, skin, and colon accounted for more than half of men's cancers; breast, colon, and skin made up half of the women's. FHS and Connecticut SEER rates matched closely, with the same primary tumor sites appearing commonly in both groups. Thus, the FHS cohort should provide a fair database for analysis of risk factors in cancer incidence, as it has done in cardiovascular diseases.

Adenocarcinoma↗

PubMed1991

Feasibility of conducting a lung-cancer chemoprevention trial among tin miners in Yunnan, P. R. China.

Tin miners in Yunnan Province in southern China have an extremely high rate of lung cancer, more than one percent per year among those at 'high risk' (40+ years old, with 10+ years of underground mining and/or smelting experience). The extraordinary lung cancer rates result from combined exposure to radon, arsenic, and tobacco smoking (cigarettes and/or bamboo water pipe). A study to determine the feasibility of conducting a large-scale, lung-cancer chemoprevention trial was conducted in 1986 among currently employed or retired miners from the Yunnan Tin Corporation in the city of Gejiu. The study was designed to answer four questions: (i) Could potentially eligible miners be identified and recruited? (ii) Could intervention agents be shipped successfully from the United States to the study area and be appropriately distributed? (iii) Would miners adequately adhere to the study protocol and comply with the intervention regimen? (iv) Could potential adverse effects be monitored and documented? The six-month feasibility study yielded affirmative answers to each of these questions. A roster of over 7,000 high-risk miners was compiled. Four agents (vitamin A, 25,000 IU; beta-carotene, 50 mg; vitamin E, 800 IU; and selenium, 400 micrograms) were administered daily with placebos to 350 miners according to a 2(4) factorial design. Adherence, assessed by pill counts and serum micronutrient levels, was approximately 90 percent. The findings from this preliminary study indicate that a full-scale, lung-cancer chemoprevention trial in this population is feasible.

Adult↗

PubMed1991

Quantitative assessment of the genotoxicity of fecapentaenes.

Fecapentaenes are a group of fecal mutagens of microbial origin isolated from human stools. Fecapentaene-12 (F-12) and fecapentaene-14 (F-14), differing only in two carbon atoms in the side chain, are glyceryl ethers with a highly reactive chromophoric aliphatic side chain incorporating a conjugated pentaene moiety. Although these compounds are known for their genotoxicity, no test systems have been developed to precisely assess their relative genotoxicity. In this study F-12 and F-14 were assayed for their genotoxicity using the SOS Chromotest in which the induction of beta-galactosidase in E. coli PQ37 was used as a quantitative measure of biological activity. The activity obtained with F-12 and F-14 was compared with that of 4-nitroquinoline oxide (4-NQO) as the reference standard of a direct acting mutagen. While F-14 was almost as active as 4-NQO, F-12 was only about 25% as active as F-14, the higher analog.

4-Nitroquinoline-1-oxide↗

PubMed1991

Is the serum cholesterol-coronary heart disease relationship modified by activity level in older persons?

Although coronary heart disease remains a leading cause of death and disability in old age, the relationship of serum cholesterol level to risk of coronary heart disease in old age is controversial. Data for 2,388 white persons aged 65-74 who participated in the National Health and Nutrition Examination Survey (NHANES) I Epidemiologic Follow-up Study (NHEFS) were examined to determine the relationship of serum cholesterol level to coronary heart disease incidence and whether activity level would modify this relationship. While there was no overall relationship between serum cholesterol level and coronary heart disease risk in either men or women, the relationship between serum cholesterol level and coronary heart disease differed within activity groups. For persons who were more active, serum cholesterol level was associated with a graded increase in risk of coronary heart disease, from 1.3 (95% CI 0.7, 2.3) in those with serum cholesterol level of 4.7-5.1 to 1.7 in those with serum cholesterol level of 6.2 mmol/L or more (95% CI 1.0, 2.7), when compared with those with serum cholesterol level below 4.7. For the least active persons, all levels of cholesterol were associated with a significant inverse relative risk, including cholesterol of 6.2 mmol/L or more (Relative risk = 0.4 (95% CI 0.2, 0.7]. These data suggest that factors such as activity level may modify the serum cholesterol-coronary heart disease association in old age. The serum cholesterol-coronary heart disease association in more active older persons resembles that seen in younger populations, whereas the association in less active persons is that of serum cholesterol level and risk of cancer or death. The modification of the serum cholesterol-coronary heart disease association by activity level may have implications for appropriate clinical management as well as appropriate design of research studies of this association.

Aged↗

PubMed1991

Dietary diversity in the US population, NHANES II, 1976-1980.

The extent of diversity in the diets of black and white adults (n = 11,658) aged 19 to 74 years was evaluated from 24-hour dietary recalls obtained in the second National Health and Nutrition Examination Survey. Each 24-hour recall was evaluated for the consumption of items from the dairy, meat, grain, fruit, and vegetable groups (Food Group Score). A second scoring method (Serving Score) evaluated every recall for consumption of at least two servings each from dairy, meat, fruit, and vegetable groups and four servings from the grain group. Only a third of the population surveyed reported consuming foods from all the food groups on the survey day; less than 3% reported consuming foods from all food groups in at least the recommended amount. Blacks scored lower on both types of diet diversity scores than whites. Both types of diversity scores showed a significant trend to increase with increasing income and level of education. Failure to consume any foods from the dairy, meat, grain, fruit, and vegetable groups was reported by 24%, 6%, 5%, 46%, and 18%, respectively, of the population on the survey day. The proportion of the population consuming at least the desired number of servings from each of these food groups was 51%, 71%, 29%, 29%, 61%, respectively. The results emphasize the need for major public campaigns directed at increasing the diversity of US diets. Special target groups include minorities and those with limited income and formal education.

Adult↗

PubMed1991

Food group intake patterns and associated nutrient profiles of the US population.

We developed a method for evaluating food group intake patterns using dietary recall data (n = 11,529) from the second National Health and Nutrition Examination Survey. We used this method to examine the relationship of these food group intake patterns to nutrient intake and to selected biochemical indexes of nutritional status. We evaluated each 24-hour dietary intake recall for the presence or omission of five broad food groups--dairy, meat, grain, fruit, and vegetable. The five most prevalent patterns and the proportion of the population reporting them was as follows: all food groups, 33.6%; no fruit, 23.9%; no dairy and fruit, 9.0%; no dairy, 8.0%; and no fruit and vegetable, 5.6%. In the most prevalent pattern, all food groups were consumed; this was the only pattern that provided mean amounts of all of the key vitamins and minerals at levels greater than or equal to the Recommended Dietary Allowances (RDAs). This pattern also was reported by the lowest proportion of individuals consuming less than 100% RDA of the key nutrients. Patterns in which both fruit and vegetables were consumed were associated with highest levels of serum vitamin C. The consistency of these results indicates that screening diets for food group consumption can quickly provide meaningful information about their quality.

Adult↗

PubMed1991

Antioxidant micronutrients in cancer prevention.

Antioxidant micronutrients are one of the body's primary defenses against free radicals and reactive oxygen molecules. Carotenoids, vitamin C, and vitamin E trap these molecules, and selenium is an essential component of an antioxidant enzyme. There is considerable support from animal studies for a protective effect of antioxidant micronutrients on cancer. However, the role of these micronutrients in cancer prevention in humans is less clear. Diet studies suggest protective effects of fruits and vegetables on risk of cancer at several sites. Inverse associations between dietary carotenoids and serum beta-carotene and lung cancer have been observed repeatedly. Vitamin C has also been consistently inversely associated with risk of oral and esophageal cancer in diet studies and with stomach cancer in both diet and plasma studies. It remains unknown, however, whether carotenoids and vitamin C or some other component of fruits and vegetables, the primary sources of these micronutrients, prevent cancer in humans. Selenium has been inversely correlated with cancers at numerous sites in ecologic studies, but observational studies do not provide strong support for a protective effect of selenium on cancer at any site. There also is not strong support for a protective effect of vitamin E on cancer in humans. Results of studies on the association of antioxidant micronutrients with cancer at many sites are inconsistent. This could be due to lack of a true protective effect or could be related to methodologic problems in assessing dietary intake in epidemiologic studies.

Animals↗

PubMed1990

Validation of intermediate end points in cancer research.

Investigations using intermediate end points as cancer surrogates are quicker, smaller, and less expensive than studies that use malignancy as the end point. We present a strategy for determining whether a given biomarker is a valid intermediate end point between an exposure and incidence of cancer. Candidate intermediate end points may be selected from case series, ecologic studies, and animal experiments. Prospective cohort and sometimes case-control studies may be used to quantify the intermediate end point-cancer association. The most appropriate measure of this association is the attributable proportion. The intermediate end point is a valid cancer surrogate if the attributable proportion is close to 1.0, but not if it is close to 0. Usually, the attributable proportion is close to neither 1.0 nor 0; in this case, valid surrogacy requires that the intermediate end point mediate an established exposure-cancer relation. This would in turn imply that the exposure effect would vanish if adjusted for the intermediate end point. We discuss the relative advantages of intervention and observational studies for the validation of intermediate end points. This validation strategy also may be applied to intermediate end points for adverse reproductive outcomes and chronic diseases other than cancer.

Biomarkers, Tumor↗

PubMed1990

Physical activity and risk of large bowel cancer in the Framingham Study.

We examined the relation between self-reported physical activity and large bowel cancer in a prospective cohort of men and women who participated in the Framingham Study. Self-assessments of physical activity were available from the fourth biennial examination on a total of 1906 men and 2308 women aged 30 to 62 yr in 1954. The cohort was followed for up to 28 yr and yielded 152 cases (73 men, 79 women) of large bowel cancer. Inactivity was associated with an increased risk of large bowel cancer among men but not among women. The relative risk estimates for large bowel cancer among men in the middle and lowest tertiles of a physical activity index (compared with the highest tertile) were 1.4 (95% confidence intervals, 0.8-2.6) and 1.8 (1.0-3.2), respectively. Among women the comparable estimates were 1.2 (0.7-2.1) and 1.1 (0.6-1.8), respectively. These findings were unchanged after adjustment for body mass index, serum cholesterol, alcohol, and other potentially confounding variables. The narrow range of physical activity and the minimal heavy activity reported by women in this cohort may have limited our ability to detect an association between physical activity and large bowel cancer among women.

Adult↗

PubMed1990

Serum vitamin A and subsequent development of prostate cancer in the first National Health and Nutrition Examination Survey Epidemiologic Follow-up Study.

The relation between serum vitamin A measurements made at baseline examination (1971-1975) and subsequent development of prostate cancer was examined in the National Health and Nutrition Examination Survey I Epidemiologic Follow-up Study (1981-1984). The analytic cohort consisted of 2440 men 50 years of age or older who were followed for a median of 10 years. A total of 84 men developed prostate cancer. The mean level of serum vitamin A was significantly lower (P less than 0.01) in prostate cancer cases than in noncases. Considered as a continuous variable or in quartiles, a statistically significant (P less than 0.005 or P less than 0.02, respectively) trend was observed for increased risk of prostate cancer with decreasing levels of serum vitamin A. Adjusted for age and race, men in the lowest quartile had a relative risk of 2.2 (95% confidence intervals, 1.1, 4.3) compared to those in the highest quartile. The elevated risk of prostate cancer associated with the lowest quartile of serum vitamin A levels did not attenuate with increasing time between blood drawing and diagnosis, suggesting that metabolic effects of early disease are an unlikely explanation of these results. The inverse association between serum vitamin A and prostate cancer incidence was independent of age at examination and several other possible confounding variables. This is the first prospective study of serum vitamin A and prostate cancer to include a large (84) number of cases.

Aged↗

PubMed1990

Association of change in body mass with breast cancer.

We examined the relation between maximal adult change in body mass and breast cancer in the Epidemiological Follow-up Study of the first National Health and Nutrition Examination Survey. A total of 5599 women ages 25 to 74 years at the baseline examination in 1971 to 1975 were analyzed. Adult body mass change was calculated from baseline interview questions on lowest and highest adult weights, ages at those weights, and adult height. The cohort was followed for a median of 10 years and yielded 101 cases of breast cancer. In a multivariate model adjusting for potential confounders (age, body mass, education, parity, age at first birth, menopausal status, calorie and alcohol intake, and physical activity) the relative risk estimates for the upper two tertiles of body mass gain were 1.7 (95% confidence interval, 0.9 to 3.4) and 2.5 (95% confidence interval, 1.2 to 5.4), respectively, in comparison to the lowest tertile of adult body mass gain. The relative risk estimate for those with a loss in body mass during adulthood was 1.3 (95% confidence interval, 0.7 to 2.6) in comparison to those in the lowest tertile of adult body mass gain. There was no association between body mass at the baseline examination and subsequent breast cancer. The results of this study suggest that gain in adult body mass is a predictor of breast cancer risk independent of adult body mass. These results also suggest that avoidance of marked weight gain during adult life may reduce the risk of breast cancer.

Alcohol Drinking↗

PubMed1990

Body fat distribution and breast cancer in the Framingham Study.

We examined the relation between central body fat distribution and breast cancer in a prospective cohort of women who participated in the Framingham Study. At the baseline examination in 1948, a total of 2,201 women aged 30-62 years were analyzed. An index of central to peripheral body fat (the central adiposity ratio) was calculated from the sum of the trunkal skinfolds (chest, subscapular, and abdominal) divided by the sum of the extremity skinfolds (triceps and thigh). These skinfolds were measured at the fourth examination in 1954. The cohort was followed for up to 28 years and yielded 106 cases of breast cancer. When divided into quartiles based on the central adiposity ratio, only women in the fourth quartile (those with the highest central to peripheral body fat distribution) demonstrated an increased risk for breast cancer. The age- and adiposity-adjusted relative risk estimate for having an increased central adiposity ratio (fourth quartile) compared to lower central adiposity ratios was 1.8 (95% confidence interval, 1.2-2.6). Adjustment for potential confounders of height, parity, and education did not appreciably alter this estimate (1.7, 1.1-2.5). There was no association between degree of adiposity, as measured by the sum of the five skinfolds or by body mass index (weight in kg divided by height in m2), and subsequent breast cancer. The results of this study suggest that increased central to peripheral body fat distribution predicts breast cancer risk independently of the degree of adiposity and may be a more specific marker of a premalignant hormonal pattern than degree of adiposity.

Adult↗