| Abstract: | Background/Aims Little information exists on breast cancer survival rates according to molecular profiles among different race/ethnic groups. We investigated the impact of molecular subtypes on breast cancer-specific survival by race/ethnicity in a large group of medically-insured women diagnosed with breast cancer. Methods The cohort included 20,749 diverse Kaiser Permanente Southern California (KPSC) women diagnosed with breast cancer (AJCC Stage 0-IV) between 1996 and 2007, and followed through 2009. The women's cancers were classified into four main molecular subtypes: luminal A (ER+ and/or PR+/HER2-); luminal B (ER+ and/or PR+/HER2+); basal-like ("triple negative", ER-/PR-/HER2-); and HER2+/ER-. The outcome was breast cancer mortality. Follow-up began on the date of surgery and ended on date of death, health plan disenrollment, or study's end. Hazard rate ratios (HR) and 95% confidence intervals (CI) were estimated using Cox proportional hazards models. We adjusted for age, tumor characteristics, cancer treatments, income, and comorbidity. Results Of the 20,749 women, 65% were white non-Hispanic (n=13,487); 13% Black (n=2,697); 12% Hispanic (n=2,490); and 10% Asian (n=2,075). We observed 2,019 deaths (10%) deaths due to breast cancer over 14 years of follow-up. In all race/ethnic groups combined, breast cancer mortality was higher in women with basal-like (HR 2.90, 2.38-3.53) and HER2+/ER- (HR 1.98, 1.55-2.54) tumors compared to women with luminal A subtype (referent group). In addition, we examined breast cancer mortality in each molecular subtype, stratified by race/ethnic group. Among women with luminal A tumors, Black women were more likely to die of breast cancer (HR 1.53, 1.02-2.29) than white women (referent group). In women with luminal B tumors, South Asians had a 10-fold increase in breast cancer mortality (HR=10.57, 1.42-78.64) compared to whites; however, numbers were small and the confidence interval was wide. Among women with basal-like tumors, Black women had a greater mortality risk (HR 1.36, 1.02-1.82) compared to white women. In women with HER2+/ER- tumors, breast cancer mortality was similar across the race/ethnic groups. No other comparisons were significant. Discussion Despite similar access to healthcare, we found survival disparities by race/ethnic groups within the luminal A, luminal B, and basal-like molecular subtypes of breast cancer. |
