Abstract PO-173: Spatial heterogeneity and rural-urban differences in the Black-White breast cancer mortality disparity in Georgia
Authors: Nash Rebecca J. , McCullough Lauren E. , Pierce T.J. , Collin Lindsay J. , Gaglioti Anne H. , Ward Kevin C. , Kramer Michael , Switchenko Jeffrey 
Published: January 2022

Abstract
Introduction: Breast cancer mortality in the US is 40% higher among Black than White women. Even among patients with prognostically favorable tumors, disparities persist, suggesting clinical features do not fully account for mortality differences. Area-level factors (e.g., rurality) influence health outcomes and may explain spatial variation in mortality disparities. Rurality can impact access to and quality of care, and socioeconomic status. Georgia is an ideal place to study spatial heterogeneity in race disparities because of the diverse population (&gt;30% Black), large number of counties (159), and pronounced disparities in breast cancer mortality in the Atlanta area. Methods: Race-specific standardized mortality ratios (SMRs) were calculated for each county in Georgia to account for sparsely populated areas and areas with high residential segregation. Observed deaths among women diagnosed with localized or regional breast cancer between 2005 and 2013 were obtained from the Georgia Cancer Registry. To ensure equal follow-up, only deaths within five years of diagnosis were included. Expected deaths were estimated using race-specific population counts, race-specific breast cancer incidence rates, and the pooled (Black and White) mortality rate among Georgia women, with indirect age adjustment (20–44, 45–54, 55+ years). Spatial smoothing methods, including adding neighboring data to meet a threshold and Bayesian models with conditionally autoregressive priors, were used to stabilize local estimates. Counties were classified by 2013 RUC codes (urban: 1–3, rural: 4–9). Results: A total of 3,235 breast cancer deaths were observed during the study period, with 42% among Black women. The median SMR was lower for White (0.8, IQR: 0.7, 1.1) than Black women (1.4, IQR: 1.1, 2.0). Among Black women only, median SMR was greater in rural (1.7, IQR: 1.1, 2.5) than urban counties (1.3, IQR: 1.1, 1.6). After sequentially adding neighboring data to meet a race-specific threshold of 30 observed deaths, smoothed median SMRs were 0.9 (IQR: 0.8, 0.9) and 1.4 (IQR: 1.2, 1.6) for White and Black women, respectively. For Black women, median SMR was attenuated in rural counties (1.4, IQR: 1.2, 1.7) but unchanged in urban counties (1.3, IQR: 1.2, 1.5). The greatest SMRs for Black women were observed in urban counties comprising the Atlanta area and rural southeast Georgia. For example, Fulton County SMRs were 1.6 and 0.7, for Black and White women, respectively. Highest SMRs for White women were observed in southwest Georgia, but were similar to SMRs among Black women in this region. The spatial distribution of SMRs using same neighbor smoothing and Bayesian models were similar. Conclusion: Breast cancer mortality race disparities vary widely across Georgia. These results highlight specific areas for public health intervention, especially among Black women. This work presents a potential mechanism to monitor trends in small area cancer mortality race disparities over time. Future work will model the impact of area-level factors on the disparity magnitude.
Citation Format: Rebecca J. Nash, Lauren E. McCullough, T.J. Pierce, Lindsay J. Collin, Anne H. Gaglioti, Kevin C. Ward, Michael Kramer, Jeffrey Switchenko. Spatial heterogeneity and rural-urban differences in the Black-White breast cancer mortality disparity in Georgia [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-173.