Abstract PR11: Temporal patterns of breast cancer treatment initiation and completion among black and white women in the Carolina Breast Cancer Study
Authors: Mayer Sophie E. , Troester Melissa , Wheeler Stephanie B. , Olshan Andrew , Carey Lisa A. , Tse Jessica , Reeder-Hayes Katherine E. 
Published: February 2019

Black women suffer from a persistent disparity in breast cancer mortality after controlling for prognostic and sociodemographic factors, suggesting that differential receipt or efficacy of treatment may contribute to their poorer outcomes. Black women are more likely to experience delays in diagnostic workup and initiation of treatment, but it is not known whether i) timeliness of subsequent care is also impacted, and ii) racial disparities in time to treatment initiation and completion persist among black and white women with comparable clinical and sociodemographic characteristics.

The Carolina Breast Cancer Study Phase III is a large population-based cohort of North Carolina women newly diagnosed with breast cancer. This study was restricted to black and white women undergoing surgery for the treatment of nonmetastatic disease. We investigated mean differences in the distribution of time from diagnosis to earliest surgery, chemotherapy, or radiation treatment (treatment initiation) and once started, time to treatment completion (treatment duration) by race. Only treatment-oriented surgeries excluding biopsies were included in this analysis, and last or definitive surgery was defined as the final treatment-oriented surgery occurring prior to recurrence and within 18 months of diagnosis. Cumulative incidence curves were used to graphically examine the distributions of time to treatment initiation and treatment duration, and general linear models were used to estimate crude and adjusted mean differences in time to treatment initiation and duration between black and white women. We also conducted stratified analyses to examine racial disparities by age and stage at diagnosis, hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) positivity, treatment pathway (surgery only, surgery plus chemotherapy, surgery plus radiation, or all three modalities), marital status, education level, income, and insurance type.

A total of 1,328 black and 1,331 white women met study inclusion criteria. Overall, black women had an average of 3.68 additional days to treatment initiation and 34.26 days longer treatment duration than white women, for 37.94 days longer total treatment time (95% confidence interval (CI): 34.21-41.67). Adjustment for clinical and sociodemographic factors resulted in a greater estimated mean difference in time to initiate treatment (4.04 days, 95% CI: 3.08-5.00), while it attenuated the mean difference in treatment duration towards the null (9.07 days, 95% CI: 6.82-11.32).

Black women experienced significantly longer time to initiate treatment and treatment duration in nearly every stratum of clinical or sociodemographic factor examined. Black women with stage II or III tumors had significantly longer time to initiate treatment than white women (4.50 and 7.84 days, respectively), and after starting treatment, treatment duration was approximately 25 days longer for black women with stage I and II disease. Black women undergoing radiation and/or chemotherapy had longer time to initiate treatment and significantly longer treatment durations. Having a college education or higher or being insured through Medicaid were associated with the greatest mean differences in time to treatment initiation comparing black and white women. Younger age at diagnosis, HR+ or HER2- disease, being unmarried, having less than a high school education, and being uninsured were associated with the greatest mean differences in treatment duration by race.

Overall, black women experienced longer intervals between diagnosis and treatment initiation and greater treatment durations after controlling for clinical and sociodemographic factors. Racial disparities were more pronounced in examination of treatment duration, suggesting that interventions to improve care coordination and timeliness should be targeted at high-risk groups.

Citation Format: Sophie E. Mayer, Melissa Troester, Stephanie B. Wheeler, Andrew Olshan, Lisa A. Carey, Jessica Tse, Katherine E. Reeder-Hayes. Temporal patterns of breast cancer treatment initiation and completion among black and white women in the Carolina Breast Cancer Study [abstract]. In: Proceedings of the Tenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2017 Sep 25-28; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2018;27(7 Suppl):Abstract nr PR11.