Search PubMed⌕ Search

Biomedical subjects

J S Witte

Publications and source records attributed to J S Witte.

49 records · Page 3Linked to original sources
PubMed1997

Family history of prostate cancer in patients with localized prostate cancer: an independent predictor of treatment outcome.

PURPOSE: To determine if familial prostate cancer patients have a less favorable prognosis than patients with sporadic prostate cancer after treatment for localized disease with either radiotherapy (RT) or radical prostatectomy (RP). PATIENTS AND METHODS: One thousand thirty-eight patients treated with either RT (n = 583) or RP (n = 455) were included in this analysis. These patients were noted as having a positive family history if they confirmed the diagnosis of prostate cancer in a first-degree relative. The outcome of interest was biochemical relapse-free survival (bRFS). We used proportional hazards to analyze the effect of the presence of family history and other potential confounding variables (ie, age, treatment modality, stage, biopsy Gleason sum [GS], and initial prostate-specific antigen [iPSA] levels) on treatment outcome. RESULTS: Eleven percent of all patients had a positive family history. The 5-year bRFS rates for patients with negative and positive family histories were 52% and 29%, respectively (P < .001). The potential confounders with bRFS rates were iPSA levels, biopsy GS, and clinical tumor stage; treatment modality and age did not appear to be associated with outcome. After adjusting for potential confounders, family history of prostate cancer remained strongly associated with biochemical failure. CONCLUSION: This is the first study to demonstrate that the presence of a family history of prostate cancer correlates with treatment outcome in a large unselected series of patients. Our findings suggest that familial prostate cancer may have a more aggressive course than nonfamilial prostate cancer, and that clinical and/or pathologic parameters may not adequately predict this course.

Aged↗
PubMed1996

Relation of vegetable, fruit, and grain consumption to colorectal adenomatous polyps.

Previous studies suggest that colorectal cancer risk decreases with higher intake of vegetables, fruits, and grains. Few studies, however, have examined these factors in relation to occurrence of colorectal polyps. The authors used case-control data from 488 matched pairs to evaluate associations of vegetables, fruits, and grains with polyps. Subjects were southern Californians aged 50-74 years who had a sigmoidoscopy in 1991-1993. Diet in the year before sigmoidoscopy was measured with a food frequency questionnaire. Frequent consumption of vegetables, fruits, and grains was associated with decreased polyp prevalence. Specifically, the adjusted odds ratio comparing the highest with the lowest quintile of intake for vegetables was 0.47 (95% confidence interval (CI) 0.29-0.76), for fruits was 0.65 (95% CI 0.40-1.05), and for grains was 0.55 (95% CI 0.33-0.91). The authors also found inverse associations for high carotenoid vegetables, cruciferae, high vitamin C fruits, garlic, and tofu (or soybeans). After further adjusting for potentially anticarcinogenic constituents of these foods, high carotenoid vegetables, cruciferous vegetables, garlic, and tofu (or soybeans) remained inversely associated with polyps. These findings support the hypothesis that high intake of vegetables, fruits, or grains decreases the risk of polyps and suggest that any protective effects might reflect unmeasured constituents in these foods.

Adenomatous Polyposis Coli↗
PubMed1996

Plasma ferritin, iron intake, and the risk of colorectal polyps.

High iron exposure has been associated with colorectal neoplasia in several studies. The authors investigated plasma ferritin, an indicator of iron stores, and iron intake as risk factors for adenomatous polyps, intermediate markers for colorectal cancer. During 1991-1993, they collected fasting blood samples from and administered questionnaires to men and women 50-75 years old who visited free sigmoidoscopy clinics at a health maintenance organization. Data from 965 subjects (467 cases, 498 controls) were analyzed. Compared with those who had low-normal plasma ferritin concentrations (73-141 micrograms/liter), those with elevated concentrations ( > 289 micrograms/liter) had a multivariate-adjusted odds ratio of 1.5 (95% confidence interval (CI) 1.0-2.3) after excluding subjects with possible non-iron-related elevations in ferritin. Compared with subjects consuming an adequate amount of iron (11.6-13.6 mg/day), multivariate-adjusted odds ratios were 1.6 (95% CI 1.1-2.4) for < 11.6 mg/day and 1.4 (95% CI 0.9-2.0) for > 27.3 mg/day. These results provide further support for a weak positive association between iron exposure and colorectal polyps.

Aged↗
PubMed1996

Simulation study of hierarchical regression.

Hierarchical regression - which attempts to improve standard regression estimates by adding a second-stage 'prior' regression to an ordinary model - provides a practical approach to evaluating multiple exposures. We present here a simulation study of logistic regression in which we compare hierarchical regression fitted by a two-stage procedure to ordinary maximum likelihood. The simulations were based on case-control data on diet and breast cancer, where the hierarchical model uses a second-stage regression to pull conventional dietary-item estimates toward each other when they have similar levels of food constituents. Our results indicate that hierarchical modelling of continuous covariates offers worthwhile improvement over ordinary maximum-likelihood, provided one does not underspecify the second-stage standard deviations.

Bayes Theorem↗
PubMed1996

Association within twin pairs for a dichotomous trait.

We propose an odds-ratio measure of twin association for a dichotomous trait. This odds ratio can be estimated without arbitrarily specifying an index twin and without estimating additional nuisance parameters. Tests of association and confidence intervals may be computed easily, in contrast to those proposed previously [Donner et al. (1995) Genet Epidemiol 12:267-277] for a correlation measure of association. For testing homogeneity of association in two samples of twins, monozygotic and dizygotic, we propose a large-sample test and an exact test, both based on the odds-ratio parameterization. Large-sample tests of homogeneity are slightly anticonservative when some cell counts are small, and the exact test may be preferred in these situations. We also propose a long-linear parameterization useful for modeling more complex data sets.

Attention↗
PubMed1996

A case-control study of reproductive variables, alcohol, and smoking in premenopausal bilateral breast cancer.

Premenopausal bilateral breast cancer is characterized by a strong family risk, and, consequently, a high probability that inherited susceptibility genes may be segregating in these families. Determining whether risk factors that affect other breast cancer cases have a similar effect in the etiology of bilateral breast cancer is of interest. Therefore, as part of an ongoing genetic-epidemiologic study of premenopausal bilateral breast cancer, we conducted a case-control analysis of reproductive variables, benign breast disease, alcohol, and smoking. Cases had premenopausal bilateral breast cancer, and their unaffected sisters served as controls. A set of reproductive variables--including earlier age at menarche, nulliparity, and late age at first full term pregnancy--appeared to increase the risk of breast cancer; the corresponding confidence limits, however, were wide and straddled the null. In addition, other variables associated with increased premenopausal bilateral breast cancer risk were: use of oral contraceptives, history of benign breast disease, and high alcohol consumption. We found no positive association for smoking. Nulliparity and late age at first full-term pregnancy appeared to have different effects in women with family histories of breast cancer than in women without such a history. We detected no substantial effect modification for the other risk factors. In general, risk factors previously identified for breast cancer (usually postmenopausal, unilateral cases) appear also to increase the risk for premenopausal, bilateral breast cancer.

Age Factors↗
PubMed1996

Agreement in alcohol consumption levels as measured by two different questionnaires.

OBJECTIVE: We evaluated the agreement in reported alcohol consumption between a standard food frequency questionnaire (FFQ) and a risk factor questionnaire (RFQ) developed for a genetic epidemiologic study of breast cancer. METHOD: The FFQ measured intake of alcoholic beverages by asking which of nine levels were consumed during a single time period. In contrast, the RFQ used open-ended questions to measure intake of alcoholic beverages during numerous time periods. Subjects (N = 765) completed both questionnaires at home. RESULTS: Mean daily alcohol consumption levels were consistently higher in the FFQ than in the RFQ; for example, the mean alcohol consumption for all subjects was 7.0 g/day in the FFQ versus 5.3 g/day in the RFQ. Moreover, the RFQ overestimated the number of nondrinkers relative to the FFQ. Nonetheless, the Spearman correlation coefficients between daily alcohol consumption levels as measured by the two questionnaires were relatively high: total alcohol, r = 0.72; beer, r = 0.69; wine, r = 0.69; and distilled spirits, r = 0.54. CONCLUSIONS: The reasonable agreement between these questionnaires supports the validity of historical alcohol consumption levels measured by the RFQ.

Adult↗
PubMed1995

Genetic epidemiologic analysis of quantitative phenotypes using Gibbs sampling.

We analyzed two quantitative traits (Q1 and Q2) provided in the 'Common Disease' data set with the aim of detecting both genetic and environmental determinants. We used linear regression for screening measured variables, maximum likelihood segregation and linkage analyses for detecting and localizing unmeasured genes, and Gibbs sampling for joint segregation and linkage analyses with estimation of gene-environment interaction and polygenic effects. For both Q1 and Q2, we successfully detected the unmeasured codominant major gene (MG) that was tightly linked to candidate gene C2. We also detected all of the measured variables used in generating Q1 (age, Q3, candidate gene C5) and Q2 (EF). Although our final models differed slightly from the true data generation models, our multifaceted analytic approach was successful in characterizing the determinants of Q1 and Q2.

Alleles↗
PubMed1994

Hierarchical regression analysis applied to a study of multiple dietary exposures and breast cancer.

Hierarchical regression attempts to improve standard regression estimates by adding a second-stage "prior" regression to an ordinary model. Here, we use hierarchical regression to analyze case-control data on diet and breast cancer. This regression yields semi-Bayes relative risk estimates for dietary items by using a second-stage model to pull estimates toward each other when the corresponding variables have similar levels of nutrients. Unlike classical Bayesian analysis, however, no use is made of previous studies on nutrient effects. Compared with results obtained with one-stage conditional maximum-likelihood logistic regression, our hierarchical regression model gives more stable and plausible estimates. In particular, certain effects with implausible maximum-likelihood estimates have more reasonable semi-Bayes estimates.

Bayes Theorem↗
PubMedDate not supplied

Red cell and plasma folate, folate consumption, and the risk of colorectal adenomatous polyps.

Epidemiological and experimental evidence suggests that dietary folate may protect against colorectal carcinogenesis. The epidemiological relationship between a biochemical measure of folate status and colorectal neoplasia in a sizeable and generally healthy population does not yet appear to have been reported. We conducted a case-control study of the relationships among red cell folate, plasma folate, folate intake, and adenomatous polyps, intermediate markers for colorectal cancer. During 1991-1993, fasting blood samples were assayed and dietary and nondietary risk factor questionnaires were administered to men and women ages 50-75 years who had a free sigmoidoscopy at a health maintenance organization. We analyzed data from 682 subjects (332 cases and 350 controls), controlling for potential confounding by sex, age, sigmoidoscopy date, and clinic. For red cell folate levels 160 ng/ml (363 nmol/liter) or more, compared to lower levels, the odds ratio was 0.76 [95% confidence interval (CI) = 0.53-1.08]. For men, the corresponding odds ratio was 0.53 (CI = 0.32-0.87); for women, it was 1.16 (CI = 0.67-2.00). Results were essentially unchanged when adjusted for levels of blood nutrients and other potential confounding variables. Plasma folate and folate intake results were similar to red cell folate results, but the associations with polyps were weaker. Results are consistent with a protective effect of red cell folate concentration against the development of colorectal polyps, at least in men. A folate effect may depend on sex-specific interactions with other nutritional or physiological factors.

Adenomatous Polyps↗