Abstract
Although racial disparity is well described for oncologic outcomes, factors associated with survival within racial groups remains unexplored. The objective of this study is to determine whether breast cancer survival among White or Black patients is associated with differing patient factors. Women diagnosed with breast cancer from 1998 through 2012 were identified in the Surveillance, Epidemiology, and End Results (SEER) database. Cox proportional hazard logistic regression was used to estimate cause-specific survival in the combined cohort, and separate cohorts of Black or White patients only. Main outcomes included cause-specific survival in cohorts of Black only, White only, or all patients adjusted for demographic and oncologic factors. A total of 406,907 Black (10.8%) or White (89.2%) patients diagnosed with breast cancer from 1998 through 2012 were isolated. Cancer-specific survival analysis of the combined cohort showed significantly decreased hazard ratio (H.R.) in patients from the higher economic quartiles (Q1: 1.0 (ref), Q2: 0.95 (p<0.01), Q3: 0.94 (p<0.01), Q4: 0.87 (p<0.001)). Analysis of the White only cohort showed a similar relationship with income (Q1: 1.0 (ref), Q2: 0.95 (p<0.01), Q3: 0.95 (p<0.01), Q4: 0.86 (p<0.001)). However, analysis of the Black only cohort did not show a relationship with income (Q1: 1.0 (ref), Q2: 1.04 (p = 0.34), Q3: 0.97 (p = 0.53), Q4: 1.04 (p = 0.47)). A test of interaction confirmed that the association between income and cancer-specific survival is dependent on patient race, both with and without adjustment for demographic and oncologic characteristics (p<0.01). While median county income is positively associated with cancer-specific survival among White patients, this is not the case with Black patients. Similar findings were noted for education level. These findings suggest that the association between socioeconomic status and breast cancer survival commonly reported in the literature is specific to White patients. These findings provide insight into differences between White and Black patients in cancer-specific survival.
Highlights
Racial disparity in survival has been reported for multiple cancer types including breast, prostate, colorectal, pancreatic, and lung[1,2,3,4]
Adjusted Cox regression analysis of the combined cohort showed that Black patients have significantly worse hazard of death when compared with White patients (HR 1.33 (1.28, 1.37) v. 1.00, p
We found that median county family income and education, which have been shown to be associated with survival in patient cohorts combining White and Black patients, were not associated with survival among the cohort of Black patients despite inclusion of over 40,000 patients [11]
Summary
Racial disparity in survival has been reported for multiple cancer types including breast, prostate, colorectal, pancreatic, and lung[1,2,3,4]. Using the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked database, Silber et al have previously shown that among patients older than 65 years old, Black patients have worse survival than White patients[2]. They attributed these findings primarily to differences in presentation; even after matching on presentation characteristics (e.g. tumor stage, size, grade, hormone status), they noted differences in treatment which may account for additional disparity. These studies have established racial disparity when comparing White and Black patients, an improved understanding of how patient factors associate with survival among patients of each race separately is required in order to guide intervention
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