Breast cancer molecular subtypes association with clinical outcomes and race.

Abstract

e12575 Background: Breast Cancer (BC) has been classified into four subtypes: Luminal A (LABC), Luminal B (LBBC), Triple negative (TNBC) and HER2-enriched (HER2e). BC mortality in Black women is significantly higher than in Whites and Asians. BC in Blacks has been characterized by higher grade and later stage. Causes of the Black-White BC survival disparity have been investigated, including differences in: diagnostic stage, socioeconomics, and comorbidities. These have led researchers to investigate the differences in tumor molecular subtype and their association with clinical outcomes and races. Methods: This study used the Surveillance, Epidemiology, and End Results – 18 (SEER-18) Registries research data between 2010 and 2013 that included over 212,000 patients. Descriptive statistics, Odds ratios (OR) and 95%Confidence intervals (CI) were used to study the association between BC stage, grade, and mortality and BC molecular subtypes across different races. We employed Cox regression models to explore the race disparity in BC mortality before and after controlling for BC molecular subtype and other clinical and social factors. Results: TNBC had more high grade cancer compared to HER2e subtype (OR, 1.5; CI, 1.3 - 1.8), LBBC (OR, 4.5; CI, 4.0 - 5.0) and LABC (OR, 12.2; CI, 11.2 – 13.3) for Black. BC mortality was higher in TNBC subtype compared to HER2e subtype (OR, 1.3; CI, 1.1 - 1.6), LBBC (OR, 2.4; CI, 2.0 - 2.9), and LABC (OR, 2.8; CI, 2.4 – 3.2) for Blacks. Results are consistent for all races. HER2e subtype had more late cancer stage compare to LBBC (OR, 1.2; CI, 1.0 - 1.4), TNBC (OR, 1.4; CI, 1.2 - 1.6) and LABC (OR, 2.1; CI, 1.8 - 2.4) in Blacks with similar results in all races. BC mortality in Blacks was higher compare with Whites (HR, 1.9; CI, 1.8 - 2.0) and Asian (HR, 2.7; CI, 2.5 - 3.0). After controlling for cancer subtype and other factors in the Cox regression model, the corresponding HRs ware significantly decreased to 1.2 (CI, 1.1 -1.3) and 1.6 (9CI, 1.5 -1.8). Blacks have heighst percent in stage IV and grade higer grade of disease. Conclusions: Molecular subtypes of BC contribute differently to risks of late cancer stage, high cancer grade and BC specific mortality. These differences are consistent in all races. The molecular subtypes and other social and clinical factors may explain part of the BC mortality race disparity.