Social Constructions, Biological Implications: A Structural Examination of Racial Disparities in Breast Cancer Subtype.

Abstract

The triple-negative subtype of breast cancer is etiologically and clinically distinct from the more common, less aggressive, and more treatable form of estrogen receptor-positive breast cancer. Numerous population-based studies have found that black women are 2 to 3 times more likely to develop triple-negative breast cancer than white women. Much of the existing research on racial disparities in breast cancer subtype has focused on identifying predisposing biological or genetic factors associated with African ancestry. However, this approach ignores growing multidisciplinary evidence suggesting that contemporary racial stratification shapes a wide range of environmental and social exposures that can subsequently impact cellular physiology and even gene expression patterns. Geronimus’ weathering hypothesis provides a unique conceptual framework through which to consider how psychosocial and environmental stressors may structure the disruption of biological mechanisms according to race. Building upon this framework, my dissertation (1) integrates important findings from stress biology, breast cancer subtype, and health disparity research in the form of a critical literature review, (2) develops an alternative conceptual model for the examination of racial disparities in breast cancer subtype, and (3) tests aspects of the model in two empirical analyses, using a combination of state-wide cancer registry data, block group-level Census and American Community Survey data, individual-level reports of stress and discrimination, and daily cortisol decline, a purported biological measure of chronic stress exposure. My findings suggest that there are significant associations between neighborhood characteristics (i.e., socioeconomic status and racial composition) and odds of more aggressive breast cancer subtypes, particularly within highly segregated metropolitan areas. However, these associations differ by race/ethnicity and across age groups. In a separate study population, the same neighborhood sociodemographic features are also associated with significant variation in daily cortisol decline. Taken together, this work demonstrates the potential for alternative biopsychosocial pathways linking race to the risk of triple-negative breast cancer, and suggests new avenues for research and public health action.