Clinicopathologic and flow cytometry features in African American and Caucasian breast cancer patients

Background: African American (AA) women experience a disproportionately high breast cancer mortality rate, and are known to have a younger age distribution for the disease compared to Caucasian (C) women. These patterns have prompted speculation that ethnicity-related factors may account for differences in breast tumor biology, yet little is known about ethnicity-related variation in breast tumor molecular markers and proliferative indices. Methods: Pathologic and flow cytometry data were analyzed for a series of 531 consecutive breast cancer patients (347 AA, 184 CI with grossly apparent/measureable tumors undergoing definitive surgery in an urban comprehensive cancer center between 1992 and 1997. Chi-squared and t-test statistical analyses were applied. Findings: Mean ages for the AA and C patients were similar (57.6 compared to 57.8 years) however 11% of the AA patients and 5% of the C patients were under the age of 40 years (p=0.04). Comparison of AA and C patients revealed that AA patients had significantly larger size tumors (mean tumor size 3.8 cm vs 3.1 cm; p=0.01); AA patients were more likely to have estrogen receptor negative tumors (53% vs 37%; p=0.001) and progesterone receptor negative tumors (59% vs 41%; p=0.001); and the mean S-phase fraction (SPF) was significantly higher for the tumors of AA patients (11.4% vs 9.6%; p=0.006). The ethnicity-related difference in mean SPF was most marked for node positive patients (AA-12.4 vs C-9.6; p=0.0006), and for patients with estrogen receptor negative tumors (AA-15.0 vs C-13.0; p=0.04). Conclusions: This study demonstrates the increased prevalence of young age at diagnosis and poor prognostic features for AA breast cancer patients. Our findings suggest that breast tumors of AA patients may accumulate more abnormal DNA with advanced stages of disease compared to C breast cancer patients. Further studies of ethnicity-related variation in breast tumor biology are warranted.