Centered Partition Process: Informative Priors for Clustering

There is a very rich literature proposing Bayesian approaches for clustering starting with a prior probability distribution on partitions. Most approaches assume exchangeability, leading to simple representations in terms of Exchangeable Partition Probability Functions (EPPF). Gibbs-type priors encompass a broad class of such cases, including Dirichlet and Pitman-Yor processes. Even though there have been some proposals to relax the exchangeability assumption, allowing covariate-dependence and partial exchangeability, limited consideration has been given on how to include concrete prior knowledge on the partition. For example, we are motivated by an epidemiological application, in which we wish to cluster birth defects into groups and we have prior knowledge of an initial clustering provided by experts. As a general approach for including such prior knowledge, we propose a Centered Partition (CP) process that modifies the EPPF to favor partitions close to an initial one. Some properties of the CP prior are described, a general algorithm for posterior computation is developed, and we illustrate the methodology through simulation examples and an application to the motivating epidemiology study of birth defects

Meeting Report: The Use of Newborn Blood Spots in Environmental Research: Opportunities and Challenges

IntroductionDried blood spots (DBS) are routinely collected from newborns in the United States using a heel stick. The DBS are screened for inborn errors of metabolism and other disorders. More states are keeping residual spots and making them available for research purposes. DNA extraction from the DBS has been widely applied; however, the development of methods to measure a range of environmental toxicants in DBS has been a more recent goal for laboratory scientists and epidemiologists.ObjectivesThe purpose of the meeting was to examine the utility of DBS to measure environmental exposures. Speakers and discussants were invited to present data and discuss approaches to measure a range of analytes using DBS.ResultsThis meeting was held on 20 February 2007 at the University of North Carolina at Chapel Hill. The audience consisted of epidemiologists, chemists, and staff from state public health programs, the Centers for Disease Control and Prevention, and the National Institutes of Health. The meeting included presentations on measurement of flame-retarding chemicals and pesticides, metals, perchlorate, infectious agents, markers of immune status, and protein adducts. Analytical methods included mass spectrometry, atomic absorption, molecular methods, and microfluidic techniques. Significant progress was reported, but important challenges remain. Concerns including storage conditions, sample volume, contamination, and normalization require additional systematic evaluation. In addition, DBS storage and access policies require coordination.ConclusionsDBS remain a highly valuable resource for clinical, epidemiologic, and toxicologic investigation. The use of DBS to measure environmental exposures shows promise but additional work is necessary before more widespread use is warranted

Associations of Premenopausal Hysterectomy and Oophorectomy With Breast Cancer Among Black and White Women: The Carolina Breast Cancer Study, 1993–2001

Black women experience higher rates of hysterectomy than other women in the United States. Although research indicates that premenopausal hysterectomy with bilateral oophorectomy decreases the risk of breast cancer in black women, it remains unclear how hysterectomy without ovary removal affects risk, whether menopausal hormone therapy use attenuates inverse associations, and whether associations vary by cancer subtype. In the population-based, case-control Carolina Breast Cancer Study of invasive breast cancer in 1,391 black (725 cases, 666 controls) and 1,727 white (939 cases, 788 controls) women in North Carolina (1993–2001), we investigated the associations of premenopausal hysterectomy and oophorectomy with breast cancer risk. Compared with no history of premenopausal surgery, bilateral oophorectomy and hysterectomy without oophorectomy were associated with lower odds of breast cancer (for bilateral oophorectomy, multivariable-adjusted odds ratios = 0.60, 95% confidence interval: 0.47, 0.77; for hysterectomy without oophorectomy, multivariable-adjusted odds ratios = 0.68, 95% confidence interval: 0.55, 0.84). Estimates did not vary by race and were similar for hormone receptor–positive and hormone receptor–negative cancers. Use of estrogen-only menopausal hormone therapy did not attenuate the associations. Premenopausal hysterectomy, even without ovary removal, may reduce the long-term risk of hormone receptor–positive and hormone receptor–negative breast cancers. Varying rates of hysterectomy are a potentially important contributor to differences in breast cancer incidence among racial/ethnic groups

Examining the Relationship Between Uterine Fibroids and Dyspareunia Among Premenopausal Women in the United States

Despite estimates of a high prevalence of deep dyspareunia (DD) among women in the US, risk factors for this important area of sexual dysfunction have been largely understudied

Alcohol intake and invasive breast cancer risk by molecular subtype and race in the Carolina Breast Cancer Study

Alcohol is an established breast cancer risk factor, but there is little evidence on whether the association differs between African Americans and whites

A collaborative study of the etiology of breast cancer subtypes in African American women: the AMBER consortium

Breast cancer is a heterogeneous disease, with at least five intrinsic subtypes defined by molecular characteristics. Tumors that express the estrogen receptor (ER+) have better outcomes than ER− tumors, due in part to the success of hormonal therapies that target ER+ tumors. The incidence of ER− breast cancer, and the subset of ER− cancers that are basal-like, is about twice as high among African American (AA) women as among U.S. women of European descent (EA). This disparity appears to explain, in part, the disproportionately high mortality from breast cancer that occurs in AA women. Epidemiologic research on breast cancer in AA women lags behind research in EA women. Here, we review differences in the etiology of breast cancer subtypes among AA women and describe a new consortium of ongoing studies of breast cancer in AA women

Quantification of arsenic, lead, mercury and cadmium in newborn dried blood spots

AbstractExposures to heavy metals during fetal and perinatal development are of particular concern. Yet, the health impacts of exposures to toxic metals during these early stages of human development are not well understood due to the paucity of in vivo human data. Dried blood spots (DBS), collected by public health departments to screen for inherited metabolic errors and other disorders, are routinely archived and can be used for exposure assessment. Here we report an improved method for quantifying arsenic, lead, mercury and cadmium in newborn DBS to facilitate epidemiologic research on the health effects of early exposures to toxic metals

Active smoking and risk of Luminal and Basal-like breast cancer subtypes in the Carolina Breast Cancer Study

Growing evidence suggests an association between active cigarette smoking and increased breast cancer risk. However, the weak magnitude of association and conflicting results have yielded uncertainty and it is unknown whether associations differ by breast cancer subtype

Household Pesticides and the Risk of Wilms Tumor

BACKGROUND: Previous epidemiologic studies have suggested that exposure to pesticides in utero and during early childhood may increase the risk for development of childhood cancer, including Wilms tumor, a childhood kidney tumor. OBJECTIVES: In this analysis we evaluated the role of residential pesticide exposure in relation to the risk of Wilms tumor in children using data from a North American case–control study. METHODS: The National Wilms Tumor Study Group (NWTSG) collected information on exposure to residential pesticides from the month before pregnancy through the diagnosis reference date using detailed phone interviews from 523 case mothers and 517 controls frequency matched on child’s age and geographic region and identified by list-assisted random digit dialing. Pesticides were grouped according to type of pesticide and where they were used. RESULTS: A slightly increased risk of Wilms tumor was found among children of mothers who reported insecticide use [odds ratio (OR) = 1.4, 95% confidence interval (CI), 1.0–1.8; adjusted for education, income, and the matching variables]. Results from all other categories of pesticides were generally close to the null. CONCLUSIONS: This study is the largest case–control study of Wilms tumor to date. We were unable to confirm earlier reports of an increased risk for Wilms tumor among those exposed to residential pesticides during pregnancy through early childhood

Understanding racial differences in health-related quality of life in a population-based cohort of breast cancer survivors

Although racial disparities in health-related quality of life (HRQOL) among women with breast cancer (BC) are well documented, less is known about HRQOL changes over time among women of different races. Our objective was to assess racial differences in HRQOL during active treatment and survivorship phases of BC care