Ki67 can be used as a predictive factor for the effectiveness of neoadjuvant chemotherapy in breast cancer patients

Cell proliferation, as measured by Ki67, is considered a significant predictive factor for the success of neoadjuvant chemotherapy (NACT) in breast cancer. However, its clinical utility remains debated. This study aimed to determine the optimal cut-off value for Ki67 and evaluate its predictive potential in this context. This study analyzed 74 patients with locally advanced breast cancer undergoing NACT. The response to NACT was assessed using the pathological complete response (pCR) rate and the neoadjuvant response index (NRI). All patients had centrally evaluated Ki67 levels alongside other tumor characteristics. The optimal cut-off value for Ki67 was determined using receiver operating characteristic (ROC) curve analysis, and its predictive potential was confirmed through univariate and multivariate analyses. A Ki67 cut-off value of 50% was identified as optimal for predicting both pCR rate and NRI. Patients with high Ki67 (>= 50%) achieved an NRI of 0.49, compared to 0.32 in patients with Ki67 <50% (p < 0.01). Similarly, the pCR rate was 19.4% in the high Ki67 group versus 5.3% in the low Ki67 group, although this difference did not reach statistical significance (p = 0.06). The independent predictive value of the Ki67 cut-off was confirmed through multivariate analysis. Cell proliferation measured by Ki67 serves as a critical predictor of response to NACT. A cut-off value of 50% can effectively identify patients more likely to achieve favorable outcomes and a higher probability of pCR.