Prognostic value of Ki67 expression in HR-negative breast cancer before and after neoadjuvant chemotherapy

Background: Immunohistochemical (IHC) expression of Ki67 has been identified as a prognostic and predictive marker in hormone receptor (HR)-positive breast cancer, however, there is little evidence of the association of Ki67 with prognosis in HR-negative patients. We aimed to assess the benefit of Ki67 assessment in HR-negative breast cancers after neoadjuvant chemotherapy (NAC). Methods: In the present study, a total of 183 HR-negative breast cancer patients with Stage II to III that treated with anthracycline and/or taxane-based neoadjuvant chemotherapy between 2004 and 2011 were retrospectively analyzed. Endocrine therapy and trastuzumab was not administered to any patients in this study. Clinical and pathological features of the patients with breast cancer were retrieved from the hospital records. Predictive factors for NAC response and survival were analyzed. Results: Of the 183 patients, 122 (66.6%) were HR-HER2+, and 61 (33.3%) were triple-negative. The clinical response rates were similar across breast cancer subtype. Patients whose tumors contained high Ki67 expression effectively responded to NAC. Ki67 labeling index was a predictive marker for pathologic complete response (pCR). Ki67 expression showed a positive correlation with HER2 status, tumor size, lymph node status, lymphovascular invasion and tumor grade. Furthermore, high Ki67 expression in post-treatment tumors was strongly correlated with poor disease-free survival (DFS), but no correlation of Ki-67 expression with overall survival (OS) was observed. Conclusions: Our results suggest that Ki67 expression in HR-negative breast cancer may improve the assessment of pathological response after NAC, and Ki67 score in residual tumor was an independent prognosticator for DFS in the HR-negative breast cancer patients.