Abstract
156 Background: To understand the origins of racial disparities in breast cancer outcomes, the relative importance of race must be examined in the context of molecular subtype. We assessed racial differences in progression-free survival (PFS) and overall survival (OS) in relation to subtype in a cohort of uniformly treated stage II-III breast cancer patients. Methods: We reviewed records of 582 consecutive 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 44.7 months. Patients: 24% black, 76% white, 55% pre/peri-menopausal. Disease: stage II 30%, stage III 70%. Treatment: all had mastectomy and PMRT; 98% had chemotherapy. All ER+ patients received endocrine therapy. Black and non-black patients were similar in age, menopause status, stage, and completion of trimodality therapy. Black patients were more likely to be ER- (56% vs 38%, p=0.0001), PR- (69% vs 54%, p=0.002), and triple negative (TN) (46% vs 24%, p<.0001). Among ER+, there were no differences in menopause or PR status by race. Black patients had worse PFS (60.6% vs 78.3%, p=.001) and OS (72.8% vs 87.7%, p<.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<.001) and OS (73% vs 91%, p<.0001). The difference in PFS was seen in the ER+/PR+/HER2- (“luminal A”) subgroup (p=.002) but not ER+/PR-/HER2- (“luminal B”) (p=0.129), and in the post-menopausal ER+/HER2- subgroup (p=.004) but not pre/perimenopausal ER+/HER2- (p=.150). On multivariate analysis, racial differences in PFS (p=.055) and OS (p=.052) were maintained in the luminal A postmenopausal subgroup. Conclusions: In a cohort of breast cancer patients black women had worse survival. This disparity was driven by (1) a higher proportion of ER- and TN tumors in the black women and (2) worse outcome of similarly treated post-menopausal black women with luminal A breast cancer. The efficacy of various types of endocrine therapy must be examined in the setting of racial diversity.
