Purpose: The prognostic value of Ki-67 in triple-negative breast cancer (TNBC) is yet unclear because the cut-off points employed differ widely and its predictive effect may vary according to age. The purpose of this study was to analyze the role of Ki-67 among patients with TNBC, and determine the optimal Ki-67 cut-off point to demonstrate its prognostic relevance associated with patient age and treatment strategy.
Methods/patients: 201 consecutive patients treated for primary TNBC from 1999 to 2014 were analyzed. Clinicopathological characteristics and outcomes were compared between patients treated with neoadjuvant or adjuvant chemotherapy. We used time-dependent receiver operating characteristic (ROC) curve and time-dependent area under the ROC curve (AUC) to evaluate the discriminative ability of Ki-67 at 3 and 5 years of follow-up. A Ki-67 cut-off point that maximized sensibility and specificity was established. Interaction effect between age and Ki-67 on disease-free survival (DFS) and overall survival (OS) was evaluated by stratified analysis.
Results: According to the coordinates of the ROC curves, the best cut-off point for Ki-67 was 60% (high/low). In the whole group, there was not a statistically significant association between Ki-67 and OS and DFS, using a cut-off point of 60%. In multivariate analysis (COX proportional hazards regression), for DFS high Ki-67 (> 60%) was a poor prognostic factor in patients > 40 years old and a better prognostic factor among the patients < 40 years old.
Conclusion: Prognostic value of Ki-67 in TNBC, using a cut-off point of 60%, may vary depending on age.
Keywords: Age; Ki-67; Prognosis; Triple-negative breast cancer.