Search PubMed⌕ Search

Biomedical subjects

B S Pasternack

Publications and source records attributed to B S Pasternack.

At least 37 records · Page 2Linked to original sources
PubMed1990

Simultaneous assessment of risk factors for malignant melanoma and non-melanoma skin lesions, with emphasis on sun exposure and related variables.

The purpose of this case-control study was to identify differences in risk factors between melanoma and non-melanoma skin lesions. The study group, interviewed from 1979 to 1982, consisted of 289 subjects with melanoma, 75 subjects with non-melanoma sun-related skin lesions and 527 controls. Simultaneous comparison of the three subgroups was accomplished by polychotomous logistic regression. The highest exposure category of lifetime sun exposure was associated with a nearly threefold risk of both melanoma and non-melanoma. Poor tanning was associated with an approximately twofold risk of both disease types. Similarly, northern European ethnicity was associated with an approximately twofold risk of disease. Number of moles on the body exhibited a relationship with melanoma only: having more than 25 moles, compared to their absence, was associated with a thirteenfold risk of melanoma. History of freckling was associated with a twofold risk of melanoma, but no increase in the risk of non-melanoma. Alternatively, mixed indoor-outdoor recreational exposure was associated with a 50% increased risk of non-melanoma, but a 25% decreased risk of melanoma. History of severe sunburn was associated with a twofold risk of non-melanoma only. For history of prior sun-related lesions the nearly sevenfold risk of melanoma was exceeded by the 14-fold risk of non-melanoma.

Case-Control Studies↗
PubMed1989

Sun exposure and malignant melanoma among susceptible individuals.

The purpose of this case-control study was to identify susceptible subgroups, primarily based on pigmentary characteristics, at higher risk of developing melanoma when exposed to the sun. The study group, which was interviewed from 1979 to 1982, consisted of 289 consecutive patients with melanoma and 527 randomly selected controls without cancer. In general, the risk of melanoma associated with sun exposure was greater for individuals expected to be susceptible on the basis of poor ability to tan, but not other pigmentary traits. There were, in addition, some noteworthy interactions between age and sun exposure. Among subjects with poor tanning ability, the risk of melanoma associated with outdoor occupation was more than 3-fold [odds ratio (OR) = 3.3] compared to indoor occupation. In contrast, the analogous OR was much less elevated among subjects with a good ability to tan (OR = 1.5). Mixed indoor and outdoor job exposure was protective among good tanners (OR = 0.80), but not among poor tanners (OR = 1.5). A similar pattern was seen for recreational sun exposure and, when applying multiple logistic regression, for the patient's overall subjective assessment of his lifetime sun exposure. However, quantitative assessment of average hours of sun exposure did not prove to be a good indicator of melanoma risk, even among susceptible individuals. A history of severe sunburn with blistering was associated with nearly 3-fold risk among poor tanners (OR = 2.9) but was protective among good tanners (OR = 0.79). A history of nonmelanoma skin cancer or solar keratosis was a very strong risk factor (OR = 7.3), which, however, did not significantly differ in magnitude among susceptibility subgroups.

Adult↗
PubMed1987

Breast cancer detection centers and case-control studies of the efficacy of screening.

Case-control studies of screening efficacy have been proposed as a cost- and time-efficient alternative to randomized controlled trials. Possible source populations for such retrospective studies of breast cancer screening are considered, including women from (i) pre-existing randomized trials, (ii) non-experimental population-based studies and (iii) detection centers. On practical grounds women attending detection centers are seen to comprise the most readily accessible source of adequate numbers of cases and controls. Potential biases are addressed, involving incomplete case ascertainment, self-selection, and different screening recommendations. Data from the Guttman Breast Diagnostic Institute are used for illustration.

Age Factors↗
PubMed1987

An industry-wide study of respiratory cancer in chemical workers exposed to chloromethyl ethers.

An industry-wide retrospective cohort mortality study was conducted on 6,152 chemical workers (2,460 exposed and 3,692 nonexposed) engaged in chloromethyl ether manufacture at 7 major U.S. companies between 1948 and 1980. A previous study at 6 companies from 1948 through 1972 reported excess respiratory cancer (RC) mortality and significant exposure-response relationships in exposed workers at 1 company (company 2). The present study, which extended follow-up of an additional 7 years for companies 1-6 and included company 7 for follow-up from 1953 through 1980, found excess RC mortality in exposed workers at company 2 [observed (Obs) = 32, standardized mortality ratio (SMR) = 430] and company 7 (Obs = 9, SMR = 603). External comparisons of RC mortality at both companies showed significant exposure-response relationships with respect to cumulative time-weighted exposure. At company 2, where the greatest number of RC deaths occurred, external comparisons showed that RC risk remained constant in relation to age at first exposure and decreased with increasing time since last exposure. With the use of Mantel-Haenszel and relative risk (RR) regression methods, internal comparisons at company 2 demonstrated significant findings of increasing RR with cumulative duration of exposure and cumulative time-weighted exposure and with decreasing time since last exposure. No association was found between RR and age at first exposure. An interesting finding was a significant negative interaction between cumulative time-weighted exposure and age at risk. The best-fitting logistic regression model for the exposed group predicted RR at 2.79 (95% confidence interval = 1.66-4.69) for workers with the mean cumulative exposure score of the 32 RC deaths (lagged by 6 yr) compared with those with negligible exposure (assuming mean age at risk of the RC deaths, 51 years old, and time since last exposure held constant). Qualitative assessment of the results suggests that chloromethyl ether exposure affects both an early as well as a late stage of a putative multistage respiratory malignant process.

Adult↗
PubMed1986

Risk assessment for case-control subgroups by polychotomous logistic regression.

Case-control studies involving more than two disease and referent categories may be analyzed by means of polychotomous logistic regression, an extension of the usual dichotomous logistic regression model. Although the standard method still may be used to compare the several disease subgroups in pairs, the polychotomous approach is advantageous in that it allows simultaneous estimation of the disease-specific parameters and direct hypothesis testing involving multiple disease categories. This is especially useful for assessing whether different disease types have different risk factors. The method is applied to a large case-control study of breast cancer involving three disease categories for which both categoric and continuous risk factors are considered. Substantive epidemiologic interpretation of polychotomous regression outputs is emphasized, as well as providing illustration of the practical aspects of the statistical method.

Adult↗
PubMed1984

A note on data monitoring, incomplete data and curtailed testing.

A question often asked in a fixed sample size clinical trial is whether the final outcome has been determined before the data has been completely collected. Recent papers in this journal and elsewhere have considered this question from the viewpoint of curtailed testing. In this paper, a related concept, "the probability of reversal" of a test procedure, is described and associated least upper bounds are given that are pertinent to the issue. The results are also of relevance in assessing, at the end of the trial, whether missing data are of consequence in the test of significance.

Clinical Trials as Topic↗
PubMed1984

Skin cancer incidence among children irradiated for ringworm of the scalp.

A series of about 2200 children who received X-ray treatment for ringworm of the scalp (tinea capitis) during the 1940s and 1950s, and a comparable group of 1400 treated without X ray, have been followed by mail questionnaire for an average of 26 years since treatment to tabulate the incidence of skin cancer. The X-ray treatment consisted of 300-380 R to five overlapping fields on the scalp, to cause complete depilation. This delivered doses of 300-600 rad to various portions of the scalp, with lower doses to the skin of the face and neck. In the irradiated group, 41 persons have had one or more basal cell carcinomas of the scalp or face while only three have been diagnosed in controls. There was a high prevalence of multiple skin cancers in the irradiated group (80 lesions among 41 cases). The minimum latent period for radiation-induced skin cancers was long--about 20 years--and this may be attributable to the young age of the population. The skin cancer risk was particularly pronounced on the face, where there would be more UVR exposure in addition to X-ray exposure. Lightness of complexion proved to be an important factor in the skin cancer risk. In addition, skin cancers were found only among caucasians, even though 25% of the study population were blacks. These findings suggest that UVR exposure levels or sensitivity to such exposure interact with ionizing radiation exposure in defining skin cancer risk.

Adolescent↗
PubMed1984

Epidemiology of minimal breast cancer among women screened in New York City.

A case-control study based on a screened population in New York City examined epidemiologic risk factor differences between minimal breast cancer (in situ and small invasive carcinomas) and all other breast carcinomas, referred to as clinical breast cancer. Histopathologic re-review of the original slides identified 113 minimal and 792 clinical breast cancers among 1,290 eligible cases; 2,173 randomly selected screenees served as controls. Among those who developed cancer, black women were twice as likely to develop minimal, as compared to clinical, breast cancer. Women who were less than 20 years of age at first live birth had more than double the probability of being diagnosed with minimal breast cancer, whereas women with first live birth at age 30 years or greater and nulliparous women were at 1.5 times the risk of clinical breast cancer. The relative proportion of minimal breast cancer increased with increasing number of children breast fed, being twofold among women who nursed 2 children or more. Unlike clinical breast cancer, minimal breast cancer was not associated with either family history of breast cancer or obesity. Meaningful histologic differences were not apparent between the case subgroups. Except possibly for obesity, these results could not be explained by any plausible diagnostic bias.

Adult↗
PubMed1984

Epidemiology of breast cancer in a screened population.

Breast cancer risk factors were examined in a screened population expected to exhibit selection bias. Data were obtained for 1,383 breast cancer cases and 2,543 randomly selected controls screened at the Guttman Breast Diagnostic Institute between 1968 and 1979. Relative risk (RR) estimates were found to be elevated for the usual factors: greater age, greater weight, early menarche, late first live birth or nulliparity, late menopause, and family history of breast cancer. Adjustment for screening variables (number of screenings, breast symptomatology, and year of first screening) removed substantial bias in RR estimates. The unadjusted analysis tended to reduce the magnitude of RR for family history and weight among screenees in general and for age among women screened only once. Although the unadjusted analysis showed no effects for either previous breast biopsy or religion, adjustment for screening variables indicated that among rescreened women, previous biopsy, Jewish and Catholic religion were associated with increased risk; among women screened once only, these characteristics were associated with decreased risk of breast cancer.

Adult↗
PubMed1982

Sample sizes for individually matched case-control studies: a group sequential approach.

This paper proposes the use of group sequential methods to calculate sample sizes for individually matched case-control study designs. A table is presented in which the average sample size required for a group sequential (i.e., multistage) matched pair design is compared to that of the conventional matched pair fixed sample size plan for the usual constant relative risk situation. The table shows that group sequential designs are in general more efficient than fixed sample size plans. Computer simulations showed that group sequential methods yield the appropriate type I and type II error rates not only for matching on a one-to-one basis, but also more generally with multiple matched controls per case. Further simulation studies indicated that there may be only a small loss of power when the matching variable(s) is associated with the probability of exposure but not with the disease. This is shown for both the multistage and fixed sample tests.

Epidemiologic Methods↗
PubMed1982

Environmental radon daughter alpha dose factors in a five-lobed human lung.

The alpha dose from 222Rn daughters per unit exposure (rad per WLM or rad per year per pCi 222Rn/m3) to basal cells in bronchial epithelium in a five-lobed human male lung is calculated. These factors are then derived for women, children and infants by scaling the dimensions of the male lung. The 222Rn daughter characteristics chosen are those typical of environmental atmospheres. Both active and resting breathing patterns are utilized in the calculations to yield the overall dose per unit exposure in typical population exposures.

Adult↗
PubMed1982

Analysis of dichotomous response data from toxicological experiments involving stable laboratory mouse populations.

The comparability between an analysis of variance that employs untransformed proportions and one that employs two common arcsine transforms is assessed by using preweaning mouse litter survival data from a toxicological experiment that involves stable laboratory populations. The importance of controlling for litter order, litter size and birth cohort is demonstrated. An adaptation of a nonparametric method suggested by Mantel (1963, Journal of the American Statistical Association 58, 690-700) is proposed as an alternative procedure. Although the results indicate that the nonparametric method is modestly less powerful than the parametric approach, its use is recommended when the assumptions underlying the analysis of variance are questionable. A method for plotting the temporal pattern of the effect of continuous exposure to the toxicant (DDT) on preweaning survival is also presented.

Analysis of Variance↗
PubMed1981

Sample sizes for group sequential cohort and case-control study designs.

This paper proposes the use of group sequential methods of calculate sample sizes for cohort and case-control study designs. The methods are based upon the theory of repeated significance tests, one of several sequential methods currently available. Group sequential methods permit repeated significance testing of relative risks obtained from periodically accumulated data while maintaining the required overall level of significance. Tables are presented for cohort and case-control studies in which the average sample size required for a group sequential design is compared to that of the conventionl fixed sample size plan for the usual constant relative risk situation. The tables show that group sequential designs are in general more efficient than fixed sample size plans for cohort and case-control studies. Computer simulations showed that group sequential methods can be employed when stratified data analyses are to be used and when the sample sizes of the two study groups are unequal.

Biometry↗