The clinical significance of Ki-67 as a marker of prognostic value and chemosensitivity prediction in hormone-receptor-positive breast cancer: a meta-analysis of the published literature

OBJECTIVES: Hormone-receptor (HR)-positive breast cancer is associated with a poor response to adjuvant chemotherapy. Thus, it is important to identify HR-positive patients who can benefit from chemotherapy and the Ki-67 index may help to predict chemotherapy efficacy in such populations. However, controversies exist regarding the prognostic and predictive role of Ki-67 and its exact cut-off value in HR-positive patients. Therefore, we conducted this study. METHODS: The meta-analysis included 4512 patients in five trials. Due to different data formats provided by studies, we classified the trials into two groups to facilitate analysis. Group 1 included the PACS01, USON 01062, and IBCSG VIII and IX trials, while Group 2 included the BCIRG001, USON 01062, and IBCSG VIII and IX trials. RESULTS: In Group 1, Ki-67 high patients had a worse prognosis in disease-free survival (DFS) than Ki-67 low counterparts (risk ratio [RR] = 1.62, 95% confidence index [CI] = 1.36-1.94, P < 0.001). In Group 2, Ki-67 high patients had a better prognosis in DFS (RR = 0.53, 95% CI = 0.45-0.61, P < 0.001) and overall survival (OS) (RR = 0.32, 95% CI = 0.25-0.42, P < 0.001). In Ki-67 high patients administered anthracycline/taxane-based chemotherapy, the experimental group (FAC → T, AC → TX) achieved a better DFS than the control group (FAC, AC → T, respectively) (RR = 0.60, 95% CI = 0.39-0.90, P = 0.014). With a cut-off point ≥19%, Ki-67 high patients achieved a worse DFS (RR = 1.49, 95% CI = 1.28-1.72, P < 0.001). CONCLUSION: This study had limitations due to its retrospective nature and the lack of standardized Ki-67 measurement methods. Nevertheless, our findings indicate that Ki-67 high patients have a worse prognosis and may be more sensitive to anthracycline/taxane-based regimens. The ideal Ki-67 cut-off point for predicting chemosensitivity may be a certain value among a range of values ≥19% in HR-positive patients.