Abstract P3-02-01: Is Ethnicity a Predictor of Micrometastatic Disease in Early Stage Breast Cancer Patients?

Abstract

Abstract Background: Ethnicity plays a role in breast cancer (BC) outcome, highlighted by the fact that African-American women have a higher BC mortality rate than do Caucasian women. Microscopic disease, including disseminated tumor cells (DTCs) in bone marrow and circulating tumor cells (CTCs) in peripheral blood, has been shown to predict worse outcomes as well. We sought to determine whether ethnicity was a significant predictor for the presence of DTCs and/or CTCs in stage I-III BC patients. Methods: Patients provided informed consent to participate in an IRB-approved study involving collection of blood and bone marrow at the time of surgery for their primary BC. CTCs (per 7.5 ml blood) were detected using the Cell SearchTM system (Veridex) and were defined as nucleated cells lacking CD45 but expressing cytokeratins (CK) 8, 18, or 19; for this study we considered one or more positive cells meeting these criteria a positive result. DTCs were assessed using an anti-CK antibody cocktail (AE1/AE3, CAM5.2, MNF116, CK8 and 18) following cytospin. A positive result for DTCs was defined by presence of one or more CK positive cells meeting morphologic criteria for malignancy. Information on clinicopathological factors including ethnicity was obtained from a prospective database. Statistical analyses used Chi-square test on STATA IC11. Results: We prospectively evaluated 224 patients undergoing surgery for stage I-III BC. Median follow-up was 22 months and mean age was 53 years. One hundred sixty seven patients (75%) were Caucasians, 22 (10%) were African-American (AA), 30 (14%) were Hispanic and 3 (1%) belonged to other ethnicities. CTCs were found in 25% (57/224) and DTCs in 30% (67/224) of patients. Patients of AA ethnicity were significantly more likely to have CTCs (50%, (11/22)) compared to the other ethnic groups (22%, (43/194)); {O.R. = 2.5, 95% C.I. = 1.35- 7.80, P = 0.002}, and had significantly higher numbers of CTCs (≥2 CTCs or ≥3 CTCs/7.5mL blood) than other ethnic groups (P = 0.001 and P < 0.001, respectively). No statistically significant correlation was observed between other ethnic groups and CTCs. Patients of Hispanic origin were more likely to have DTCs (60%, (18/30)) as compared to other ethnic groups (25%, (49/194)); {O.R. = 4.4, 95% C.I. = 1.85- 10.80, P < 0.0001}, while DTCs were less likely to be found in Caucasians (26%, (44/167)) as compared to the other ethnicities (40%, (23/57)); {O.R. = 0.52, 95% C.I. = 0.27 — 1.05, P = 0.046}. No significant association was found between occurrence of DTCs and AA ethnicity. In a multivariate analysis considering lymph node status, tumor size and tumor markers, ethnic origin was an independent predictor of microscopic disease. Conclusions: Nearly one-third of primary BC patients have CTCs and/or DTCs. African-American women were much more likely to have CTCs and Hispanic patients had significantly more DTCs than did patients of other ethnicities. Ethnicity was an independent predictor of microscopic disease. These findings may shed some light on the higher BC mortality rates found in certain ethnic groups. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-02-01.