Racial disparity in estrogen receptor positive breast cancer patients receiving trimodality therapy

Introduction: We assessed racial differences in progression-free survival (PFS) and overall survival (OS) in relation to subtype in uniformly treated stage II-III breast cancer patients. Methods: We reviewed records of 582 patients receiving post-mastectomy radiation (PMRT) between 1/1999 and 12/2009 and evaluated the effect of demographic, tumor, and treatment characteristics on PFS and OS. Results: Median follow up was 44.7 months. 24% of patients were black and 76% white. All had mastectomy and PMRT; 98% had chemotherapy; Estrogen receptor (ER)+ patients received endocrine therapy. Black patients were more likely to have ER- (56% vs. 38%, p = 0.0001), progesterone receptor (PR)- (69% vs. 54%, p = 0.002), and triple negative (TN) (46% vs. 24%, p < 0.0001) tumors. Overall, black patients had worse PFS (60.6% vs. 78.3%, p = 0.001) and OS (72.8% vs. 87.7%, p < 0.0001). There was no racial difference in PFS (p = 0.229 and 0.273 respectively) or OS (p = 0.113 and 0.097 respectively) among ER- or TN. Among ER+, black patients had worse PFS (55% vs. 81%, p < 0.001) and OS (73% vs. 91%, p < 0.0001). The difference in PFS was seen in the ER+/PR+/HER2- subgroup (p = 0.002) but not ER+/PR-/HER2- (p = 0.129), and in the post-menopausal ER+/HER2- subgroup (p = 0.004) but not pre/peri-menopausal ER+/HER2- (p = 0.150). Conclusions: Black women had worse survival outcomes in this cohort. This disparity was driven by (1) a higher proportion of ER- and TN tumors in black women and (2) worse outcome of similarly treated black women with ER+ breast cancer. The underlying causes of racial disparity within hormone receptor categories must be further examined.