Abstract P2-06-08: Race is not a contributing factor to breast cancer-free interval outcome for patients with equal access to healthcare treated at a military medical center
Authors: Liu J , Fantacone_Campbell JL , Kovatich AJ , Hooke JA , Kvecher L , Sturtz LA , Shriver CD , Hu H 
Published: March 2017

BACKGROUND Black patients diagnosed with invasive breast cancer (IBC) are more likely to die of the disease than their White counterparts. Differences in IBC subtype, socioeconomic status, and access to healthcare may be contributing factors. We performed this study to determine if there is a racial disparity in breast cancer-free interval (BCFI) for patients treated at a military medical center where equal-access healthcare is provided.

METHODS Three datasets were used: 1) TCGA-Breast Cancer cohort with 149 Black and 706 White patients; 2) Clinical Breast Care Project patients from a military medical center (CBCP-WR) with 112 Black and 372 White patients; and 3) CBCP patients from a civilian facility (CBCP-AAMC) without equal-access healthcare (data collection is ongoing and results will be available for the conference). IHC of ER, PR, and HER2 was performed to subtype IBCs as TN (ER-/PR-/HER2-) or Non-TN. Patients with Stage IV IBC at diagnosis were excluded. Kaplan-Meier method was used to generate survival plots. Cox proportional hazards regression model was used for survival analysis between races (Black vs. White). Univariable and multivariable analyses were performed. All analyses were performed using R 3.2.2. A two-tailed p value &lt; 0.05 was considered significant.

RESULTS The clinicopathologic properties of Black and White patients in TCGA and CBCP-WR cohorts were analyzed, and the results are consistent with the literature. The median follow-up times were comparable between the two races (TCGA: Black=29.4 M, White=27.5 M; CBCP-WR: Black=61.1 M, White=60.9 M).

In TCGA, race significantly affects BCFI in multivariable analysis after adjustment for age, AJCC stage, and PAM50 subtype (HR=1.73, 95%CI=1.02-2.94, p=0.042). Stratifying patients into TN (Black=46.7%; White=53.3%) and Non-TN (Black=14.2%; White=85.8%) subtypes, race trended towards significant in BCFI in TN (HR=2.33, 95%CI=0.98-5.56, p=0.052) but not Non-TN subtypes (HR=1.12, 95%CI=0.55-2.27, p=0.752). Further adjustment for age and AJCC stage did not alter the results.

In CBCP-WR, there was no significant racial difference in both univariable (HR=1.52, 95%CI=0.87-2.68, p=0.145) and multivariable analysis of BCFI adjusted for age, subtype and AJCC stage (HR=1.00, 95%CI=0.5-2.01, p=0.989). Stratifying patients into TN (Black=43.5%; White=56.5%) and Non-TN (Black=18.8%; White=91.2%) subtypes, race was not a significant factor in either group (TN: HR=0.920, 95%CI=0.4-2.14, p=0.846; Non-TN: HR=1.17, 95%CI=0.53-2.61, p=0.701). Further adjustment for age and AJCC stage did not alter the results.

CONCLUSIONS Our results show that in the CBCP-WR cohort, there is no racial disparity in BCFI at the whole cohort level nor is there any trend in the TN subtype. These results contradict those obtained from the TCGA cohort suggesting unequal healthcare access may be a major contributor to racial disparity in BCFI. Analysis of the CBCP-AAMC cohort may provide further insight into whether treatment at a single medical center needs to be considered when investigating racial disparities in BCFI.

The views expressed in this article are those of the author and do not reflect the official policy of the Department of Defense, or U.S. Government.

Citation Format: Liu J, Fantacone_Campbell JL, Kovatich AJ, Hooke JA, Kvecher L, Sturtz LA, Shriver CD, Hu H. Race is not a contributing factor to breast cancer-free interval outcome for patients with equal access to healthcare treated at a military medical center [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-06-08.