Re: Prostate cancer incidence and mortality in the United States and the United Kingdom.
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Aged↗
Biomedical subjects
A S Whittemore
Publications and source records attributed to A S Whittemore.
A genome screen of families with multiple cases of prostate cancer: evidence of genetic heterogeneity.
We conducted a genomewide screen for prostate cancer-susceptibility genes on the basis of data from 98 families from the United States and Canada that had three or more verified diagnoses of prostate cancer among first- and second-degree relatives. We found a statistically significant excess of markers for which affected relatives exhibited modest amounts of excess allele-sharing; however, no single chromosomal region contained markers with excess allele-sharing of sufficient magnitude to indicate unequivocal evidence of linkage. Positive linkage signals of nominal statistical significance were found in two regions (5p-q and 12p) that have been identified as weakly positive in other data sets and in region 19p, which has not been identified previously. All these signals were considerably stronger for analyses restricted to families with mean age at onset below the median than for analyses of families with mean age at onset above the median. The data provided little support for any of the putative prostate cancer-susceptibility genes identified in other linkage studies.
Age of Onset↗
Problems in the definition, interpretation, and evaluation of genetic heterogeneity.
Suppose that we wish to classify families with multiple cases of disease into one of three categories: those that segregate mutations of a gene of interest, those which segregate mutations of other genes, and those whose disease is due to nonhereditary factors or chance. Among families in the first two categories (the hereditary families), we wish to estimate the proportion, p, of families that segregate mutations of the gene of interest. Although this proportion is a commonly accepted concept, it is well defined only with an unambiguous definition of "family." Even then, extraneous factors such as family sizes and structures can cause p to vary across different populations and, within a population, to be estimated differently by different studies. Restrictive assumptions about the disease are needed, in order to avoid this undesirable variation. The assumptions require that mutations of all disease-causing genes (i) have no effect on family size, (ii) have very low frequencies, and (iii) have penetrances that satisfy certain constraints. Despite the unverifiability of these assumptions, linkage studies often invoke them to estimate p, using the admixture likelihood introduced by Smith and discussed by Ott. We argue against this common practice, because (1) it also requires the stronger assumption of equal penetrances for all etiologically relevant genes; (2) even if all assumptions are met, estimates of p are sensitive to misspecification of the unknown phenocopy rate; (3) even if all the necessary assumptions are met and the phenocopy rate is correctly specified, estimates of p that are obtained by linkage programs such as HOMOG and GENEHUNTER are based on the wrong likelihood and therefore are biased in the presence of phenocopies. We show how to correct these estimates; but, nevertheless, we do not recommend the use of parametric heterogeneity models in linkage analysis, even merely as a tool for increasing the statistical power to detect linkage. This is because the assumptions required by these models cannot be verified, and their violation could actually decrease power. Instead, we suggest that estimation of p be postponed until the relevant genes have been identified. Then their frequencies and penetrances can be estimated on the basis of population-based samples and can be used to obtain more-robust estimates of p for specific populations.
Family Health↗
Age at natural menopause and the risk of epithelial ovarian cancer.
OBJECTIVE: To investigate the relationship between age at natural menopause and risk of developing epithelial ovarian cancer. METHODS: Using data from six population-based, case-control studies conducted in the United States, age at natural menopause among 1411 women with epithelial ovarian cancer and 6380 control subjects were analyzed using survival analysis methods, including Kaplan-Meier and proportional hazards models. Subjects ranged from 20 to 81 years of age. RESULTS: The median age at natural menopause was 50 years among cases compared with 51 years among controls, a difference of borderline statistical significance (P =.06). The hazard ratio for the relationship between case-control status and age at natural menopause was 1.09 (95% confidence interval 0.99, 1.20). Controlling for potential confounders including parity, oral contraceptive use, tubal ligation, smoking, and body mass index did not appreciably change this association. There was little evidence of an association between early age at natural menopause and early onset ovarian cancer (diagnosis age under 48 years). CONCLUSION: We observed a weak association between ovarian cancer risk and age at natural menopause and, among women with early onset disease, there was little evidence to suggest that early menopause is related to ovarian cancer. Thus, there seems little need for increased surveillance or screening for ovarian cancer among women with early natural menopause.
Adult↗
A BRCA1 variant, IVS23+1G-->A, causes abnormal RNA splicing by deleting exon 23.
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Adenine↗
Allele-sharing among affected relatives: non-parametric methods for identifying genes.
Non-parametric linkage analysis examines similarities among affected relatives in alleles of one or more genetic markers (pieces of DNA at known locations on a chromosome). The objective is to evaluate departures from the null hypothesis that the markers are not near a disease gene. Under the null hypothesis, Mendel's laws give the probabilities that a set of relatives exhibits a particular allele-sharing pattern, and the null hypothesis is rejected if the extent of allele sharing among affected relatives exceeds Mendelian expectation. Because the rationale for allele-sharing methods is intuitively plausible and easily grasped, geneticists have used these methods for more than 30 years, well before the advent of the large sets of polymorphic markers that have made linkage analysis so fruitful today. Here we describe methods for assessing whether the extent of marker allele sharing among affected relatives exceeds Mendelian expectation. We first quantify the notion of allele sharing and the probabilities of allele sharing in various sets of relatives. Then we describe allele sharing methods for affected sibs and more general sets of relatives. We also discuss related issues of test size and power. We conclude with a brief discussion of areas in need of further research.
Alleles↗
Lifestyle determinants of 5alpha-reductase metabolites in older African-American, white, and Asian-American men.
Men with higher endogenous 5alpha-reductase activity may have higher prostate cancer risk. This hypothesis raises two questions: (a) Could racial differences in 5alpha-reductase activity explain the observed racial differences in prostate cancer risk? and (b) Could a man reduce his activity level by modifying his lifestyle? To address these questions, we measured two hormonal indices of 5alpha-reductase activity [serum levels of androstane-3alpha-17beta-diol glucuronide (3alpha-diol G) and androsterone glucuronide (AG)] in healthy, older African-American, white, and Asian-American men, who are at high, intermediate, and low prostate cancer risk, respectively. We also examined associations between these metabolite levels and such lifestyle characteristics as body size and physical activity as well as select aspects of medical history and family history of prostate cancer. Men included in this cross-sectional analysis (n = 1054) had served as control subjects in a population-based case-control study of prostate cancer we conducted in California, Hawaii, and Vancouver, Canada and provided information on certain personal attributes and donated blood between March 1990 and March 1992. In this study, concentrations of 3alpha-diol G declined significantly with age and increased significantly with body mass index. Mean levels of 3alpha-diol G, adjusted for age and body mass index, were 6.1 ng/ml in African-Americans, 6.9 ng/ml in whites and 4.8 ng/ml in Asian-Americans. These differences were statistically significant (African-Americans versus whites: P < 0.01; whites versus Asian-Americans: P < 0.001). Concentrations of AG decreased significantly with age, but only in whites, and were unrelated to any of the reported personal attributes. Mean levels of AG, adjusted for age, were 44.1 ng/ml in African-Americans, 44.9 ng/ml in whites, and 37.5 ng/ml in Asian-Americans (Asian-Americans versus whites, P < 0.001). In conclusion, older African-American and white men have similar levels of these two indices of 5alpha-reductase activity, and these levels are higher than those of older Asian-American men. This difference may be related to the lower prostate cancer risk in Asian-Americans.
Age Distribution↗
Iodine and thyroid cancer risk among women in a multiethnic population: the Bay Area Thyroid Cancer Study.
Research on the relationship between iodine exposure and thyroid cancer risk is limited, and the findings are inconclusive. In most studies, fish/shellfish consumption has been used as a proxy measure of iodine exposure. The present study extends this research by quantifying dietary iodine exposure as well as incorporating a biomarker of long-term (1 year) exposure, i.e., from toenail clippings. This study is conducted in a multiethnic population with a wide variation in thyroid cancer incidence rates and substantial diversity in exposure. Women, ages 20-74, residing in the San Francisco Bay Area and diagnosed with thyroid cancer between 1995 and 1998 (1992-1998 for Asian women) were compared with women selected from the general population via random digit dialing. Interviews were conducted in six languages with 608 cases and 558 controls. The established risk factors for thyroid cancer were found to increase risk in this population: radiation to the head/neck [odds ratio (OR), 2.3; 95% confidence interval (CI), 0.97-5.5]; history of goiter/nodules (OR, 3.7; 95% CI, 2.5-5.6); and a family history of proliferative thyroid disease (OR, 2.5; 95% CI, 1.6-3.8). Contrary to our hypothesis, increased dietary iodine, most likely related to the use of multivitamin pills, was associated with a reduced risk of papillary thyroid cancer. This risk reduction was observed in "low-risk" women (i.e., women without any of the three established risk factors noted above; OR, 0.53; 95% CI, 0.33-0.85) but not in "high-risk" women, among whom a slight elevation in risk was seen (OR, 1.4; 95% CI, 0.56-3.4). However, no association with risk was observed in either group when the biomarker of exposure was evaluated. In addition, no ethnic differences in risk were observed. The authors conclude that iodine exposure appears to have, at most, a weak effect on the risk of papillary thyroid cancer.
Adult↗
Survival in epithelial ovarian cancer patients with prior breast cancer.
Ovarian cancer patients who carry germ-line BRCA1 mutations may have improved survival compared with ovarian cancer patients without these mutations. To evaluate this hypothesis, the authors compared survival in ovarian cancer patients who had a history of prior breast cancer with that of patients without such a history. Specifically, they used data from the population-based US Surveillance, Epidemiology, and End Results (SEER) Program to assess time to death from ovarian cancer among ovarian cancer patients with and without a prior breast cancer. All 25,637 White women diagnosed with invasive epithelial ovarian cancer in SEER registries between 1973 and 1995 were included. Of these, 824 women had had a prior breast cancer diagnosis. The ovarian cancer death rate among women with prior breast cancer was significantly lower than that of women with ovarian cancer only, adjusted for age and stage at ovarian cancer diagnosis. The survival advantage was most pronounced among older women and among those whose ovarian cancers were more advanced at the time of diagnosis. These results lend indirect support to prior findings of improved ovarian cancer survival in BRCA1 mutation carriers.
Adult↗
Ovarian carcinoma in situ with germline BRCA1 mutation and loss of heterozygosity at BRCA1 and TP53.
BACKGROUND: The two-hit hypothesis for the genesis of cancer predicts that cancer can develop when the wild-type allele of a tumor suppressor gene is lost in an individual with a germline mutation in that gene. Neither loss of heterozygosity (LOH) for BRCA1 nor mutations of the TP53 (also known as p53) gene have been documented prior to invasion in ovarian cancers arising in women with germline BRCA1 mutations. Such documentation is difficult because lesions are rarely identified in ovarian epithelium. We, therefore, looked for LOH at microsatellite polymorphisms linked to the BRCA1 and TP53 tumor suppressor loci in an incidental carcinoma in situ of the ovary removed prophylactically from a woman with a germline BRCA1 mutation. METHODS: By use of laser-capture microdissection, we obtained pure populations of atypical ovarian epithelial cells and normal stromal cells. DNA was extracted, amplified with primers flanking polymorphic microsatellites linked to BRCA1 (D17S855 and D17S579) and TP53 (TP53 and D17S786), and analyzed for LOH at these microsatellites. We also tested for p53 expression in the abnormal epithelium by immunohistochemistry. RESULTS: Both of the markers linked to TP53 showed LOH, as did an intragenic BRCA1-linked marker (D17S855). The other microsatellite marker for BRCA1 was uninformative. Immunohistochemical staining with an antibody to p53 showed strong immunoreactivity confined to the atypical epithelium. CONCLUSIONS: BRCA1, as well as TP53, can undergo LOH prior to stromal invasion in BRCA1-associated ovarian cancer. Strong immunoreactivity for p53 suggests the presence of mutated p53 in these cells as well. These findings suggest that loss of function of these two tumor suppressor genes occurs early in ovarian carcinogenesis in BRCA1 mutation carriers.
Antibodies, Neoplasm↗
Detection of disease genes by use of family data. I. Likelihood-based theory.
We present a class of likelihood-based score statistics that accommodate genotypes of both unrelated individuals and families, thereby combining the advantages of case-control and family-based designs. The likelihood extends the one proposed by Schaid and colleagues (Schaid and Sommer 1993, 1994; Schaid 1996; Schaid and Li 1997) to arbitrary family structures with arbitrary patterns of missing data and to dense sets of multiple markers. The score statistic comprises two component test statistics. The first component statistic, the nonfounder statistic, evaluates disequilibrium in the transmission of marker alleles from parents to offspring. This statistic, when applied to nuclear families, generalizes the transmission/disequilibrium test to arbitrary numbers of affected and unaffected siblings, with or without typed parents. The second component statistic, the founder statistic, compares observed or inferred marker genotypes in the family founders with those of controls or those of some reference population. The founder statistic generalizes the statistics commonly used for case-control data. The strengths of the approach include both the ability to assess, by comparison of nonfounder and founder statistics, the potential bias resulting from population stratification and the ability to accommodate arbitrary family structures, thus eliminating the need for many different ad hoc tests. A limitation of the approach is the potential power loss and/or bias resulting from inappropriate assumptions on the distribution of founder genotypes. The systematic likelihood-based framework provided here should be useful in the evaluation of both the relative merits of case-control and various family-based designs and the relative merits of different tests applied to the same design. It should also be useful for genotype-disease association studies done with the use of a dense set of multiple markers.
Alleles↗
Detection of disease genes by use of family data. II. Application to nuclear families.
Two likelihood-based score statistics are used to detect association between a disease and a single diallelic polymorphism, on the basis of data from arbitrary types of nuclear families. The first statistic, the nonfounder statistic, extends the transmission/disequilibrium test to accommodate affected and unaffected offspring and missing parental genotypes. The second statistic, the founder statistic, compares observed or inferred parental genotypes with those of some reference population. In this comparison, the genotypes of affected parents or of those with many affected offspring are weighted more heavily than are the genotypes of unaffected parents or of those with few affected offspring. Genotypes of single unrelated cases and controls can be included in this analysis. We illustrate the two statistics by applying them to data on a polymorphism of the SDR5A2 gene in nuclear families with multiple cases of prostate cancer. We also use simulations to compare the power of the nonfounder statistic with that of the score statistic, on the basis of the conditional logistic regression of offspring genotypes.
Alleles↗
Differences in socioeconomic status and survival among white and black men with prostate cancer.
After diagnosis with prostate cancer, Black men in the United States have poorer survival than White men, even after controlling for differences in cancer stage. The extent to which these racial survival differences are due to biologic versus non-biologic factors is unclear, and it has been hypothesized that differences associated with socioeconomic status (SES) might account for much of the observed survival difference. The authors examined this hypothesis in a cohort study, using cancer registry and US Census data for White and Black men with incident prostate cancer (n = 23,334) who resided in 1,005 census tracts in the San Francisco Bay Area during 1973-1993. Separate analyses were conducted using two endpoints: death from prostate cancer and death from other causes. For each endpoint, death rate ratios (Blacks vs. Whites) were computed for men diagnosed at ages <65 years and at ages > or =65 years. These data suggest that differences associated with SES do not explain why Black men die from prostate cancer at a higher rate when compared with White men with this condition. However, among men with prostate cancer, SES-associated differences appear to explain almost all of the racial difference in risk of death from other causes.
Black or African American↗
Comparative study of ovarian cancer histopathology by registry pathologists and referral pathologists: a study by the Gilda Radner Familial Ovarian Cancer Registry.
OBJECTIVE: The aim of this study was to evaluate whether there is a significant difference in the pathology diagnoses of women in the Gilda Radner Familial Ovarian Cancer Registry between the two expert Registry pathologists and the referral pathologist. Inaccuracies in verification that ovarian cancer did occur in family members could lead to unnecessary prophylactic surgery or genetic testing. METHODS: A retrospective review was performed of (1) site of malignancy; (2) histopathology of malignancy; (3) grade of malignancy; and (4) the presence or absence of malignancy between the Registry and referral pathologists. RESULTS: There was 95.3% complete agreement between the Registry and the referral pathologist on site of origin with a major difference in only 1.0% of the cases. In comparison of histopathology, there was a 61.7% complete agreement, and only 1.0% were considered major differences. There was 68.8% complete agreement in grade of the malignancy, whereas 2.3% were considered major differences. CONCLUSION: When constructing a family pedigree, it is important to obtain pathology reports to confirm the index case diagnosis of the presence or absence of ovarian cancer. However, because of the small percentage of major differences in diagnosis between the two Registry pathologists and the multiple referral pathologists, we believe genetic counselors and treating physicians can rely, in most instances, on the original histopathology report of verification of ovarian cancer without review of the original histopathology slides when recommending surveillance, genetic testing, and/or prophylactic surgery.
Female↗
Pseudoautosomal linkage of Hodgkin disease.
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Chromosome Mapping↗
Declining ovarian cancer rates in U.S. women in relation to parity and oral contraceptive use.
Ovarian cancer incidence and mortality rates have declined among U.S. women age 35-59 years during the period 1970-1995. Epidemiologic studies have shown that ovarian cancer risk decreases with increasing parity and increasing duration of oral contraceptive use. During this period, parity has declined while oral contraceptive use has increased. We compared temporal trends in observed ovarian cancer incidence rates with rates predicted by changes in parity and duration of oral contraceptive use to determine whether the changes in these characteristics could explain the declining rates in younger women. In addition, we wished to examine whether oral contraceptive use continues to be protective to postmenopausal women. To predict changes in rates between 1970 and 1995, we assumed that increases in parity and duration of oral contraceptive use induce proportional decreases in incidence rates. We found that the rates predicted by these assumptions agreed well with observed rates in young women (age 30-49) but were substantially lower than observed rates in older women (age 50-64). The data indicate that the relative decrease in incidence rates due to the protective effect of oral contraceptive use declines with age.
Adult↗
Primary ovarian dysgerminoma in a patient with a germline BRCA1 mutation.
Germline mutations in the BRCA1 tumor suppressor gene are associated with increased risk for the development of ovarian cancer. All such cancers thus far reported have been of the epithelial histologic type. We identified an ovarian dysgerminoma in a 16-year-old woman (proband) with a family history of ovarian cancer during a review of histopathologic characteristics of ovarian cancers from women enrolled in the Gilda Radner Familial Ovarian Cancer Registry. Mutation analysis of DNA from this patient's peripheral blood leukocytes revealed a germline BRCA1 mutation (3312insG). The mutation was also present in the mother with breast cancer, a maternal aunt and a distant cousin with ovarian cancer, and a maternal grandfather and an uncle with skin cancer. The development of the proband's dysgerminoma may be unrelated to her germline BRCA1 mutation. Alternatively, such dysgerminomas may be caused by BRCA1 mutations, but occur so infrequently compared with epithelial cancers that they are seldom identified. Analysis of a larger series of ovarian germ cell tumors may resolve this question.
Adolescent↗
Vegetables, fruits, legumes and prostate cancer: a multiethnic case-control study.
The evidence for a protective effect of vegetables, fruits, and legumes against prostate cancer is weak and inconsistent. We examined the relationship of these food groups and their constituent foods to prostate cancer risk in a multicenter case-control study of African-American, white, Japanese, and Chinese men. Cases (n = 1619) with histologically confirmed prostate cancer were identified through the population-based tumor registries of Hawaii, San Francisco, and Los Angeles in the United States and British Columbia and Ontario in Canada. Controls (n = 1618) were frequency-matched to cases on ethnicity, age, and region of residence of the case, in a ratio of approximately 1:1. Dietary and other information was collected by in-person home interview; a blood sample was obtained from control subjects for prostate-specific antigen determination. Odds ratios (OR) were estimated using logistic regression, adjusting for age, geographic location, education, calories, and when indicated, ethnicity. Intake of legumes (whether total legumes, soyfoods specifically, or other legumes) was inversely related to prostate cancer (OR for highest relative to lowest quintile for total legumes = 0.62; P for trend = 0.0002); results were similar when restricted to prostate-specific antigen-normal controls or to advanced cases. Intakes of yellow-orange and cruciferous vegetables were also inversely related to prostate cancer, especially for advanced cases, among whom the highest quintile OR for yellow-orange vegetables = 0.67 (P for trend = 0.01) and the highest quintile OR for cruciferous vegetables = 0.61 (P for trend = 0.006). Intake of tomatoes and of fruits was not related to risk. Findings were generally consistent across ethnic groups. These results suggest that legumes (not limited to soy products) and certain categories of vegetables may protect against prostate cancer.
Aged↗