Abstract PR03: A reverse, racial disparity with respect to interval breast cancer rates within a large healthcare organization has implications for eliminating disparities more generally
Authors: Rauscher Garth H. , Dabbous Firas , Dolecek Terry , Macarol Terry , Tossas-Milligan Katherine , Khan Jenna , Friedwald Sarah , Summerfelt Wm. Thomas 
Published: May 2016

Abstract
Background: It is well established that Non Latina (nL) Black patients are more likely than nL white (white) patients to be diagnosed with more aggressive forms of breast cancer. In addition, prior population-based research conducted in Chicago suggests that black women tend to be screened at lower resource facilities, and may also have screening images of lower quality and be more likely to have their breast cancer missed at interpretation. Consistent with all of these observations, black patients were more likely to report symptomatic awareness of their breast cancer despite a recent asymptomatic screening mammogram in the Breast Cancer Care in Chicago study. Therefore, black women may be more likely than their white counterparts to have a breast cancer diagnosis following a negative screen (so-called interval breast cancer). METHODS: The goal of the present study was to examine potential disparities in interval breast cancer (IBC) using data from approximately 30 mammography sites (including 8 hospital-based sites) within a single large health care organization in metropolitan Chicago.
Methods: A screening mammogram was defined as a bilateral mammogram with a description of screening in the radiology database, in women without a prior history of breast cancer, mastectomy, or breast implants, and without any imaging in the 9 months prior to the screen. We linked 761,908 screening examinations conducted between 2001-2010 to breast cancer incidence data from the Illinois state cancer registry, using probabilistic methods. After excluding other race/ethnicities for this analysis, we identified 4829 breast cancers diagnosed between 2001 and 2011 and within 12 months of a screen. An interval breast cancer was defined as a breast cancer diagnosed within 12 months of a negative screening mammogram (BIRADS 1,2). IBC was modeled in logistic regression with generalized estimating equations (to account for multiple screens per woman) while adjusting for age, parity, breast density, race, family history, parity and exam year, ER status, tumor grade, and individual screening facility as covariates. Of the 31 facilities with data, 18 smaller screening facilities with less than 20 associated breast cancer diagnoses were collapsed into a single category. Model-based standardization (predictive margins) was used to estimate adjusted prevalence differences (PDs) in IBC from the logistic regression models, and 95% bias-corrected bootstrap confidence intervals were obtained (1000 replications).
Results: Before adjusting for mammography site, black patients were, contrary to expectation, less likely to experience an IBC than white patients (1.36 vs. 1.83 per 1000 screens, adjusted Rate Difference or RD = - 0.47 per 1000 screens, p&lt;0.0001). The proportion of screening mammograms conducted in Black women ranged from 1% to 96% across mammography sites, and IBC rates ranged across facilities from 9 per 100 screens to 29 per 1000 screens (p&lt;0.0001). After controlling for mammography site the reverse disparity in IBC disappeared and the IBC rate was negligibly higher in black than white patients (1.79 vs. 1.68 per 1000 screens, p=0.614).
Conclusion: In this large healthcare organization, we observed a reverse disparity such that white patients were more likely than their black counterparts to experience an IBC, but the association disappeared when we took mammography site into account in the analysis. These results suggest that higher quality mammography screening resources are more widely accessible to black than white patients within this organization. Larger volume facilities within this organization tend to be located in urban areas with higher proportions of black women, whereas smaller standalone facilities tend to be located in the suburbs where there are a higher proportion of white women. These standalone facilities may be less likely to employ breast imaging specialists and less likely provide multimodality breast imaging in a multidisciplinary setting, and these differences may be contributing to differential access to quality screening that benefits black women. The larger implication of these findings is that at a population level, racial disparities in breast cancer could perhaps be ameliorated or even eliminated if resources were disproportionately made more available to black women. In order to overcome breast cancer disparities and create true equity in care, disproportionate resource allocation solutions may be necessary.
This abstract is also presented as Poster C61.
Citation Format: Garth H. Rauscher, Firas Dabbous, Terry Dolecek, Terry Macarol, Katherine Tossas-Milligan, Jenna Khan, Sarah Friedwald, Wm. Thomas Summerfelt. A reverse, racial disparity with respect to interval breast cancer rates within a large healthcare organization has implications for eliminating disparities more generally. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr PR03.