To investigate the correlation between Ki67 expression change after neoadjuvant chemotherapy (NCT) and prognosis of triple negative breast cancer (TNBC) patients.

We retrospectively analyzed the clinical data of 102 TNBC patients in Zhejiang Cancer Hospital from January 2010 to December 2015. Immunohistochemistry was adopted to detect the expression of Ki67 after NCT. Patients were divided into three groups according to the change of Ki67 expression: group A, from low expression (Ki67≤20%) to high expression (Ki67>20%); group B, no change; group C, from high expression to low expression. Then the correlation of Ki67 expression change after neoadjuvant chemotherapy with efficacy was analyzed by Kruskal-Wallis test. Kaplan-Meier survival curve and COX multivariate regression model were used for survival analysis.

In 102 patients, there were 11 patients (10.8%) in group A, 49(48.0%) in group B and 42 (41.2%) in group C. Ki67 expression change was correlated with clinical response (χ²=23.617, P<0.001) and pathological response (χ²=41.412, P<0.001) of NCT. The median follow-up was 34 months. The DFS rate of group A, B and C was 36.4%, 60.4% and 88.1%, respectively. The DFS rate in group C was significant higher than that in group A (χ²=14.980, P<0.001) or group B(χ²=9.878, P=0.002). There was no significant difference in OS rate among three groups (χ²=5.683, P=0.058). According to the Cox multivariate regression model, Ki67 expression change was an independent factor of DFS (HR=0.401, 95%CI: 0.243-0.659, P<0.001) and OS (HR =0.387, 95%CI: 0.170-0.881, P=0.024).

Ki67 expression change after NCT is correlated with clinical and pathological response. Meanwhile, Ki67 expression change can also be used to predict the prognosis of triple-negative breast cancer patients, which can provide guidance for the treatment after NCT.