Abstract B43: Disparities in mortality and five-year survival by race and socioeconomic status in white and African American women diagnosed with breast cancer in metropolitan Detroit
Authors: Hastert Theresa A. , Schwartz Ann G. , Albrecht Terrance L. 
Published: October 2015

Background: Racial and, to a lesser extent, socioeconomic disparities in breast cancer incidence and mortality have been well documented; however, little is known about whether observed racial disparities differ by socioeconomic status.

Methods: We used data from the population-based Metropolitan Detroit Cancer Surveillance System to estimate hazard ratios of death for non-Hispanic white (N = 31,102, including 8,174 deaths) and African-American women (N = 9,257, including 3,133 deaths) ages 18 and older diagnosed with incident, invasive breast cancer with recorded stage between 2000 and 2013 in Oakland, Wayne, and Macomb counties in Michigan and to estimate 5-year survival percentages for women diagnosed between 2000 and 2008 (N = 18,922). Neighborhood poverty was measured using the proportion of households with incomes below the federal poverty level in 2000 in the women's census tracts of residence at diagnosis. We used Cox proportional hazards models controlling for age at diagnosis, year of diagnosis, and cancer stage at diagnosis to estimate hazard ratios (HR) and 95% confidence intervals (CI) associated with mortality. Standard errors were adjusted to account for unobserved correlation between residents of the same census tracts.

Results: Risk of death in African-American women diagnosed with breast cancer was 57% higher than for white women (HR: 1.57, 95% CI: 1.48, 1.67), and this association attenuated when also controlling for neighborhood poverty (HR: 1.31, 95% CI: 1.20, 1.42). Living in high-poverty neighborhoods was associated with a 77% higher risk of death (HR: 1.77, 95% CI: 1.64, 1.91), and this association also attenuated when controlling for race (HR: 1.46, 95% CI: 1.33, 1.62). Risk of death was higher for African-American women than for white women at every level of neighborhood poverty, although the associations were stronger in the lowest poverty areas (HR associated with being African-American: 1.68, 95% CI: 1.33, 2.12) than in the highest-poverty areas (HR: 1.23, 95% CI 1.08, 1.40). Among white women, higher neighborhood poverty was associated with higher risk of death (HR for high- vs. low-poverty areas: 1.57, 95% CI: 1.37, 1.79), but living in higher-poverty areas was not associated with mortality among African-American women with breast cancer (HR for high- vs. low-poverty areas: 1.21, 95% CI: 0.96, 1.51). Five-year survival was higher in white women (77.6%) than in African-American women (65.3%) overall. This difference in 5-year survival was largest for women living in the lowest-poverty areas (81.5% for whites vs. 70.1% for African-Americans), but was much smaller for women in the highest-poverty areas (66.2% for whites vs. 62.3% for African Americans).

Conclusions: Although important disparities in mortality exist for African-American women compared with white women with breast cancer, disparities also exist by socioeconomic status, particularly for white women. The extent to which these disparities could be due to treatment differences, age at diagnosis, and type of breast cancer is being examined. It is important to consider socioeconomic status in addition to race when identifying and addressing disparities in breast cancer outcomes.

Citation Format: Theresa A. Hastert, Ann G. Schwartz, Terrance L. Albrecht. Disparities in mortality and five-year survival by race and socioeconomic status in white and African American women diagnosed with breast cancer in metropolitan Detroit. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr B43.