Abstract A67: Do hospital characteristics explain racial/ethnic disparities in mortality after breast cancer diagnosis: The California Breast Cancer Survivorship Consortium
Authors: Shariff-Marco Salma , Kurian Allison W. , Yang Juan , Koo Jocelyn , John Esther M. , Keegan Theresa H. M. , Cheng Iona , Monroe Kristine R. , Vigen Cheryl , Kwan Marilyn L. , Lu Yani , Henderson Brian E. , Bernstein Leslie , Sposto Richard , Wu Anna H. , Gomez Scarlett L. 
Published: October 2015

Introduction: Disparities in breast cancer mortality persist between racial/ethnic groups. Little is known about the role of the treatment environment, specifically the characteristics of the hospital reporting a patient's breast cancer diagnosis. Differential access to high quality care contributes to disparities in treatment and outcomes. The California Breast Cancer Survivorship Consortium (CBCSC) integrated data on patient demographics, behavioral and reproductive characteristics from patient interviews, and on tumor characteristics, treatment, and follow-up from the California Cancer Registry. This study leveraged the large size and racial/ethnic diversity to examine the extent to which hospital characteristics explain racial/ethnic disparities in mortality following breast cancer diagnosis.

Methods: Using data from five of the six studies in the CBCSC, the study sample included 4,624 non-Latina whites, 1,849 Latinas, 1,832 African-Americans, and 1,333 Asian Americans diagnosed with Stage I-IV breast cancer between 1993 and 2007. We used study- and stage-stratified Cox regression models to assess the independent associations of hospital characteristics with mortality, and examined the change in racial/ethnic hazard ratios before and after adjustment for hospital characteristics. Hospital characteristics included composition measures based on the patients served by each hospital such as SES (percent of cancer patients from the highest quintile SES neighborhoods), race/ethnicity, and insurance type as well as NCI cancer center designation. Distance from patients' residences to hospitals was also examined. Patient sociodemographics include race/ethnicity, education, marital status, and neighborhood SES; behavioral and reproductive factors include smoking, alcohol consumption, obesity, exercise, family history of breast cancer, and parity; and clinical factors include tumor characteristics, treatment, and co-morbidities.

Results: For all-cause mortality, patients seen in high SES hospitals had lower mortality rates than those seen in low SES hospitals (HR=0.87, 95% CI=0.75-0.99). The other hospital characteristics were not associated with all-cause mortality. Compared with non-Latina whites, we observed a higher mortality rate for African-Americans (HR=1.40, 95% CI=1.23-1.58), a lower mortality rate for Latinas (HR=0.89, 95% CI=0.78-1.01) and no statistically different rate for Asian Americans (HR=0.80, 95% CI=0.60-1.07). After adjusting for hospital characteristics, the higher mortality rate observed for African-Americans was slightly attenuated (HR=1.34, 95% CI= 1.18-1.51) whereas the lower mortality rate for Latinas became slightly stronger (HR=0.86, 95% CI=0.75-0.98). No statistically significant associations were observed for breast cancer-specific mortality. We also tested for interactions between race/ethnicity and hospital characteristics and found no statistically significant interactions.

Conclusion: Hospital SES (as measured based on patient composition) is independently associated with all-cause mortality after a diagnosis of breast cancer, even after adjusting for a patient's educational level and neighborhood SES. However, adjusting for hospital characteristics accounted only slightly for the higher overall mortality rate among African-Americans and strengthened the lower mortality rate observed among Latinas. The fact that most breast cancer treatment occurs outside of hospitals may explain the lack of an observed association with disease-specific mortality; by contrast, hospital SES likely signifies a combination of factors (for example, the presence and severity of co-morbidities beyond what was measured, and access to effective care) that contribute to a gradient in all-cause mortality.

Citation Format: Salma Shariff-Marco, Allison W. Kurian, Juan Yang, Jocelyn Koo, Esther M. John, Theresa H. M. Keegan, Iona Cheng, Kristine R. Monroe, Cheryl Vigen, Marilyn L. Kwan, Yani Lu, Brian E. Henderson, Leslie Bernstein, Richard Sposto, Anna H. Wu, Scarlett L. Gomez. Do hospital characteristics explain racial/ethnic disparities in mortality after breast cancer diagnosis: The California Breast Cancer Survivorship Consortium. [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 A67.