Although racial disparities in survival after cancer surgery are no doubt multifactorial, our findings highlight the importance of hospital factors, including quality. After accounting for potentially confounding patient characteristics, black patients had substantially higher late mortality rates after surgery for breast and colon cancer than their white counterparts. For breast cancer, patient factors played a greater proportional role than hospital factors in explaining the survival disparity observed for black patients. For colon cancer, hospital factors accounted for nearly half of the excess late mortality risk, whereas patient factors explained relatively little of the disparity. Hospitals with large minority populations had significantly higher late mortality rates for both cancers among white and black patients.
Our study is not the first to demonstrate the importance of system factors in explaining racial disparities in outcomes with specific conditions or procedures. In addition to our previous study focusing on operative mortality with different procedures,10
other investigators have observed lower rates of referral to high-volume centers for minority patients when compared with whites8
and clustering of racial and ethnic minorities in a small number of centers.5
In addition, black patients have less access to high-quality surgeons,29
are more likely to experience treatment delays,2,30
and may be less likely to receive adjuvant therapy.31,32
Although our analysis demonstrates the importance of hospital factors in explaining racial disparities in late mortality after cancer surgery, it does not identify specifically what those factors are. Among potential candidates, patients cared for in poorer hospitals with fewer resources may have reduced access to processes of care such as multidisciplinary management teams and high-quality imaging technology and may be less likely to receive evidence-based adjuvant therapy after surgical resection.32–36
Such hospitals may tend to allocate their resources more toward clinical conditions most prevalent in disadvantaged groups, including trauma and emergency care and infectious diseases.
This study has several limitations. First, we studied only Medicare patients greater than 65 years of age. Although we have no reason to believe that hospital factors would be less important in mediating outcomes among younger patients, our analysis could not confirm this empirically. Our reliance on patients with Medicare insurance is a more important limitation, however. Racial disparities in late survival after cancer care may be even more pronounced in the large proportion of minority patients without insurance. Such patients may present with poorly managed comorbidities and later stage cancers (as a result of lack of screening). They may also tend to receive their care in resource-poor safety net hospitals. For these reasons, addressing systems problems and quality may be particularly important in reducing disparities in younger, uninsured populations.
Second, because we relied on administrative data to identify patient comorbidities, we may have underestimated their contribution to mortality after cancer surgery. Previous studies have documented the importance of coexisting noncancer diagnoses on prognosis.20,37–39
In additional analyses (not shown), blacks and whites had identical other-cause mortality for colon cancer (22% v
22%, respectively, at 5 years) and similar rates for breast cancer (18% v
15%, respectively). Instead, racial differences in overall mortality rates were almost entirely a result of differences in cancer-specific mortality. These data support our main conclusions that racial disparities in survival after cancer surgery relate primarily to differences in cancer care, not comorbidity prevalence or management.
A third, important limitation of this study is our lack of patient-level measures of income, education, and other socioeconomic variables associated with both race and mortality. In our analysis, area-level SES was an important mediator of relationships between race, hospital factors, and late mortality. These findings are consistent with previous research indicating that hospitals serving patients residing in areas with low SES have worse surgical outcomes independent of race.21
Although previous studies suggest that area-level SES data correlate strongly with patient-level data,40
individual-level data would be nonetheless invaluable for fully exploring the role of SES in explaining both between-hospital and within-hospital differences in survival by race.
Fourth, in our analyses of hospital racial mix and mortality, we had limited statistical power for examining potential important hospital subgroups. Only a small proportion of hospitals (11.87% in this study) served at least 20% black patients. In only 4.79% of hospitals did blacks constitute the majority. Furthermore, our study was limited to the one state and seven SEER counties with sufficiently large minority representation, further limiting the generalizability of our findings. Finally, we focused primarily on mortality in black patients versus white patients. Future studies might consider the extent to which hospital factors may be important in outcomes after cancer surgery for other racial and ethnic groups.
Understanding and ultimately reducing racial disparities in health care has become an important research and policy priority. With regard to cancer care, broad efforts aimed at both improving cancer prevention and early detection with screening are no doubt essential. However, our findings suggest that where patients obtain treatment after cancer diagnosis may be equally important. Among potential approaches to reducing hospital-related disparities, payers and policy makers could aim to direct black patients and other disadvantaged groups to hospitals and systems with better results in cancer care—so-called selective referral. Although more expedient, such strategies are currently limited by reliable data for identifying best hospitals. As implied by our results, simple measures, such as hospital procedure volume, would not be sufficient for steering black patients to centers with better outcomes and eliminating disparities. Moreover, strategies focused exclusively on selective referral might disrupt coordination of care for minority patients and have other unintended harms.
For these reasons, improving quality in the systems in which patients currently receive their cancer care is paramount. Effecting this goal will require a better understanding of structural differences and resource deficits that account for worse cancer outcomes at hospitals treating larger minority populations. A better understanding of differences in process of care is also essential. Further research in this area should aim to understand which aspects of standard treatment are poorly delivered or absent within hospitals that disproportionately serve minority patients. Perhaps more importantly, researchers should delineate better the obstacles to cancer treatment in these hospitals. Overcoming such obstacles will likely require special efforts to coordinate and deliver care, such as directed patient navigator programs and targeted community outreach. To be consistent with the goals of improving equity and quality in cancer care, these efforts should extend well beyond the current policy-based impetus to reward or penalize hospitals according to standard measures of cancer care quality.