Prognostic Significance of Basal Markers in Triple-negative Breast Cancers

Purpose: We have investigated the prognostic significance of the expression of basal markers for triple-negative (estrogen receptor-negative, progesterone receptor-negative and human epidermal growth factor receptor-2-negative) breast cancers (TNBCs). Methods: An immunohistochemical study was performed on tissue microarrays constructed with 643 invasive breast carcinoma samples. We subclassified the TNBCs into basal phenotype (BP) and non-BP groups by the use of four different criteria according to the immunprofiles for cytokeratin5/6 (CK5/6), epidermal growth factor receptor (EGFR), vimentin, c-Kit, p63 and P-cadherin. The criteria consisted of criterion 1: CK5/6+ only, criterion 2: CK5/6+ and/or EGFR+, criterion 3: CK5/6+ and/or EGFR+ and/or vimentin+ and criterion 4: one or more marker(s) positive among the six basal markers. Each of these criteria, as well as the status of each individual marker, was evaluated to estimate prognosis for TNBC patients. Results: Of the breast carcinomas, 165 cases (25.7%) were TNBCs. As compared with the non-TNBCs, TNBCs were associated with a larger tumor size (p=0.001), higher histological grade (p<0.001) and shorter overall survival (OS) (p=0.002) and disease-free survival (DFS) (p=0.05). Lymph node status, tumor size and expression of EGFR or c-Kit were independent prognostic factors for patients with TNBC. As compared with the nonBP, BP as defined by criterion 2 was an independent poor prognostic factor for OS and DFS among patients with a lymph node metastasis (p=0.044 and p=0.01) and among patients who received anthracycline-based adjuvant chemotherapy (p=0.009 and p=0.01, respectively). Conclusion: Patients with TNBCs showed a poorer prognosis as compared to patients with non-TNBCs. Selected group of the basal-like breast cancers (BLBCs) defined by the immunohistochemical profiles of basal markers showed survival differences from non-BLBCs in subgroups of TNBCs with a homogeneous clinical finding.