Abstract P6-08-01: Race and recurrence by PAM50 intrinsic subtype and ROR-PT score: The Carolina breast cancer study

Abstract Compared with white women, black women have higher breast cancer mortality. Racial differences have been reported in frequency of PAM50 intrinsic subtypes, and PAM50 intrinsic subtype is associated with prognosis. However, there is a paucity of data from large population-based studies with adequate representation of black women to evaluate its role in racial differences in breast cancer outcomes. We studied breast cancer recurrence in relation to PAM50 intrinsic subtype using data from the Carolina Breast Cancer Study Phase III (CBCS3), a large population-based prospective cohort study oversampled black women. The current analysis included 472 black and 463 white women with stage I-III tumor and available Nanostring gene expression data for PAM50 subtype and risk of recurrence score (ROR-PT, a score calculated based on subtype, proliferation level, and tumor size; categorized as low, medium, and high). Cox proportional hazard regression was used to estimate the association of recurrence with PAM50 intrinsic subtype and ROR-PT, overall and stratified by race, adjusted for tumor size, grade, and lymph node status. During a median follow-up of 5.78 years (range=0.39-8.22), 110 recurrent cases were identified (68 blacks and 42 whites). Consistently with previous data, basal-like tumors had the highest risk for recurrence (reference=luminal A, adjusted hazard ratio [HR]=2.85, 95% confidence interval [CI]=1.44-5.66), followed by luminal B (adjusted HR=2.35, 95%CI=1.18-4.69) and Her2-enriched (adjusted HR=2.19, 95%CI=1.01-4.74). High-ROR-PT score was also associated with increased risk in both black (adjusted HR=1.55, 95%CI=0.93-2.60) and white (adjusted HR=2.07, 95%CI=1.04-4.11). Recurrence rate for black women with medium/low ROR-PT scores was suggested higher than that for white women with similar scores (adjusted HR=1.54, 95%CI=0.69-3.42). Our results demonstrate that PAM50 subtype and ROR-PT score are associated with breast cancer recurrence in both black and white women. Given the higher relative frequency of poor prognosis subtypes in black women, these findings help explain prognosis disparities by race. Citation Format: Sun X, Reeder-Hayes KE, Kirk EL, Olsson L, Tse C-K, Bell MB, Earp HS, Carey LA, Perou CM, Olshan AF, Troester MA. Race and recurrence by PAM50 intrinsic subtype and ROR-PT score: The Carolina breast cancer study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-08-01.