Ki-67 Expression by Immunohistochemistry and Quantitative Real-Time Polymerase Chain Reaction as Predictor of Clinical Response to Neoadjuvant Chemotherapy in Locally Advanced Breast Cancer

Background Chemotherapy has become a standard of treatment in managing breast cancer. To achieve proper treatment for the right patients, the predictive marker is needed. Ki-67 is a biomarker of proliferation for solid tumor. Studies mentioned association of Ki-67 expression with chemotherapy response. The study aims are to evaluate whether Ki-67 expression detected by immunohistochemistry (IHC) and quantitative real-time polymerase chain reaction (qRT-PCR) may predict clinical response to neoadjuvant chemotherapy in breast cancer. Methods This study utilized a longitudinal study. IHC and qRT-PCR methods were used for detection of Ki-67 expression. Chemotherapy response was calculated using RECIST. Data were analyzed with Chi-square and Wilcoxon's test. Results There were 48 subjects in this study. Analysis of Ki-67 expression with chemotherapy response has a significant correlation with p = 0.025 (<0.05), OR: 1.69, confidence interval (95% CI) 1.022-2.810. Analysis of Ki-67 mRNA expression with chemotherapy response has a significant correlation p = 0.002 (<0.05), OR: 6.85, confidence interval (95% CI) 1.064-44.193. Detection of Ki-67 expression using IHC and qRT-PCR has similar results, p = 0.012 (<0.05). Conclusion These results suggest that Ki-67 expression detected by both IHC and qRT-PCR is considered to be a predictor of clinical response to neoadjuvant chemotherapy in locally advanced breast cancer.