Multiple mediation analysis of racial disparity in breast cancer survival

1Introduction

Despite the higher incidence rate of breast cancer in non-Hispanic White (White) women compared to their non-Hispanic Black (Black) counterparts in the 1970s, the breast cancer mortality rate in Black women began to exceed that of White women in the early 1980s [1] . The recognition that breast cancer screening via mammography reduces the likelihood of breast cancer death [23] , that women of lower socioeconomic status (SES) and minority women are less likely to be screened [3] , and the widening racial gap in breast cancer mortality/survival between Black and White women [4] led to governmental efforts to reduce barriers to screening mammography for underserved women. The best example of this is the National Breast and Cervical Cancer Early Detection Program (NBCCEDP), which aims to provide breast and cervical cancer screening to underserved women, of whom Black women are overrepresented. In addition to the NBCCEDP, federal funding for breast cancer research increased significantly during the 1990s [56] . Furthermore, campaigns by national foundations, private companies, and community efforts have increased breast cancer awareness, promotion of breast health, and screening via mammography [6] .

Since the 1980s, racial disparities in breast cancer mortality and survival have persisted despite the aforementioned laws, programs, and campaigns aimed at improving outcomes for all women, especially those that are undeserved. For example, when comparing recent data on mortality rates between Black and White women according to cancer site, breast cancer ranks first in terms of the magnitude of the disparity measured by the rate difference while ranking second on the ratio scale behind uterine cancer [7] . We recently conducted a study of trends in breast cancer survival by race and ethnicity for women in Florida diagnosed over a 26-year period [8] . Although we found that racial and ethnic disparities improved over time, Black women still experience over twice the rate of breast cancer-specific death compared to White women. As mentioned, this disparity exists despite widespread awareness of racial disparities in breast cancer outcomes and concerted efforts to eliminate them over the past several decades.

Without a better understanding of the causes of racial disparities in breast cancer survival, health policies, programs, and interventions may not achieve the desired outcome of eliminating, or at least reducing, the survival disparity between Black and White women. Mediation analysis offers an opportunity to gain insight concerning the mechanisms through which an exposure affects an outcome [9] . The purpose of this study was to conduct a multiple mediation analysis of racial disparity in breast cancer survival for women in Florida with the goal of identifying the most important mediators of the disparity. This knowledge can then be used to inform targeted evidence-based policies, programs, and interventions which may be most effective approach to achieve more equitable outcomes for Black women diagnosed with the disease.