Value of Ki-67 in prediction of response to neoadjuvant chemotherapy in breast cancer.

Abstract

e12025 Background: The expression of the human Ki-67 protein has been described as being associated with cellular proliferative activity. The objective of this study is to assess the potential value of Ki-67 for the prediction of therapeutic response after neoadjuvant chemotherapy in breast cancer. Methods: Sixty-eight patients who underwent anthracyclin based neoadjuvant chemotherapy between 2007 and 2012 were included for this study. The chemotherapy response was evaluated by comparing the pre- and post-neoadjuvant chemotherapy tumor size on radiologic imaging study with the tumor size at pathologic specimens according to RECIST (response evaluation criteria in solid tumors) version 1.1. We analyzed immunohistochemical(ER, PR, HER2, Ki-67, p53) profiles from both pre-neoadjuvant core biopsy and postoperative specimens to find their correlations with chemotherapy response. Results: Ten patients(14.7%) achieved pathologic complete response(pCR), 38 patients(55.9%) had pathologic partial response(pPR) and 20 patients(29.4%) had pathologic stable disease(pSD). The mean Ki-67 value of tumors with pCR was 61.0%, the Ki-67 value of tumors with pPR was 35.9%, and the Ki-67 value of tumors with pSD was 21.0%(p = 0.013). The analysis of Ki-67 values of the patients also showed that 25% of Ki-67 level is a reasonable cut-off value for defining higher Ki-67 level. In subgroup analysis, the higher Ki-67 level was significant factor of the response to neoadjuvant chemotherapy, especially in ER negative patients(p = 0.009) and HER2 negative patients(p = 0.009). In addition, the analaysis of response group showed that ER negative(p = 0.027), HER2 positive(p = 0.048), and higher Ki-67 level(p = 0.002) were predictive indicators of complete response. Conclusions: The higher Ki-67 level of breast cancer tissue may effectively indicate the higher response rate to chemotherapy and also the higher complete response rate. The results of our study suggest that the Ki-67 value before neoadjuvant chemotherapy is a predictive factor for the response to neoadjuvant chemotherapy. Moreover, the Ki-67 is a predictive factor of the pathologic complete response especially in patients with ER negative or HER2 positive.