Introduction: In New Mexico (NM), Hispanic women have a 1.6-fold increased risk of breast cancer-specific death compared to non-Hispanic white women. In previous studies, race/ethnic minority women have been less likely to receive recommended adjuvant treatments, including radiation in women undergoing breast conservation, and hormonal therapy.
Objective: To determine whether non-receipt of recommended therapies contributed to disparate survival.
Methods: We conducted a case-cohort study of breast-cancer-specific survival within a population-based cohort of first invasive breast cancer diagnosed in white females from 1997-2009 in six NM counties, identified through Surveillance Epidemiology End Results (SEER). We selected fifteen percent of all women diagnosed with breast cancer and all breast cancer deaths. After IRB approval, data were collected from comprehensive medical chart reviews, supplemented by SEER information. Receipt of standard of care, vs. not, was defined based on age, diagnosis year and tumor characteristics, according to changes in treatment guidelines. Women who had a reported contraindication or refused therapy were omitted from assessment of quality of care for that therapy. Cox proportional hazards models for case-cohort were conducted using weighted estimates, with calculation of robust variance and hazard ratios (HR) and 95% confidence intervals (CI), using an alpha level of .05. Analyses were restricted to women of age 70 or less who survived at least 12 months. The proportional hazards assumption was verified by Schoenfeld residuals. All analyses were adjusted for age.
Results: Comprehensive medical records reviews were completed for 91% of eligible women (674 cohort members, 519 breast cancer deaths; median follow up 7.8 years). All others were omitted from analysis. Of women eligible for guideline-based treatment, receipt of guideline-appropriate therapy did not differ by Hispanic ethnicity for any treatment, and Hispanic women were slightly more likely overall to receive appropriate therapy (difference not significant). Among guideline-eligible women, at least 91% received radiotherapy, 78% received chemotherapy, 82% received endocrine therapy, and 89% received anti-HER2 targeted agents. After adjustment for other treatment, lack of receipt of guideline-appropriate therapy was related to an increased risk of breast cancer death for endocrine (HR 1.76; 95% CI 1.09-2.84) and radiation therapy (HR 2.05; 95% CI 1.14-3.69). The few HER2-positive women not treated precluded further assessment. After accounting for endocrine and radiation therapy the survival disparity HR of 1.6 in Hispanic women was reduced to 1.57 suggesting only 2% of the disparity was due to differences in receipt of these treatments.
Conclusion: Limitations include likely undercounts of appropriate therapy, thus proportions cited are minimal estimates. Appropriate therapy includes only documented receipt as therapy completion could not always be assessed. Hispanic women have a disproportionately higher breast cancer mortality despite apparently receiving adjuvant therapies to a similar degree as non-Hispanic white women. Equalizing standard of care and attempting to reduce treatment disparities may not be sufficient to address the disproportionate mortality in Hispanic women.
Citation Format: Friend SC, Royce ME, Kang H, Lomo L, Barry M, Wiggins C, Prossnitz E, Hill DA. Survival disparities: Quality of care apparently not the answer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-09-05.