Effects of socioeconomic status and race on survival and treatment in metastatic breast cancer

Race and socioeconomic factors affect outcomes in breast cancer. We aimed to assess the effect of race and neighborhood socioeconomic status (SES) on overall survival and treatment patterns in patients with metastatic breast cancer (MBC). This is a retrospective cohort study involving patients (N = 1246) with distant breast cancer metastases diagnosed at UPMC Magee Women's Breast Cancer Clinic from 2000-2017. Overall survival and treatment patterns were compared between races (Blacks and whites) and SES groups (defined using Area Deprivation Index). Low SES, but not tumor characteristics, was associated with Black race (P < 0.001) in the study population. Low SES (Median [Interquartile Range, IQR] survival 2.3[2.2-2.5] years vs high SES 2.7[2.5-3.1] years, P = 0.01) and Black race (Median [IQR] survival 1.8[1.3-2.3] years, vs white 2.5[2.3-2.7] years P = 0.008) separately were associated with worse overall survival in patients with MBC. In the Cox Proportional Hazard model with SES, race, age, subtype, number of metastases, visceral metastasis, and year of diagnosis as covariates, low SES (Hazard ratio 1.19[1.04-1.35], P = 0.01), but not Black race (Hazard ratio 1.19[0.96-1.49], P = 0.12), independently predicted overall survival in MBC. Moreover, patients from low SES neighborhoods and Black race received fewer lines of chemotherapy than high SES and whites. In conclusion, low neighborhood SES is associated with worse outcomes in patients with MBC. Poor outcomes in Black patients with MBC, at least in part is driven by socioeconomic factors. Future studies should delineate the interplay between neighborhood SES, race, and their effects on tumor biology in MBC.