Abstract P5-16-13: Predictive and prognostic value of Ki-67 expression in triple-negative breast cancer before and after neoadjuvant chemotherapy with weekly paclitaxel plus carboplatin

Abstract

Abstract Background: Neoadjuvant chemotherapy (NCT) is one of the main treatment strategies for patients with locally advanced breast cancer. This study was designed to demonstrate the utility of a platinum-containing treatment regimen in the neoadjuvant setting and to identify the predictive or prognostic value of Ki-67 among patients with triple-negative breast cancer (TNBC) Methods: Data from 280 patients with stage II–III TNBC were collected. All patients underwent four cycles of NCT with paclitaxel (80 mg/m2) and carboplatin (AUC 2 mg*min/ml) on days 1, 8, and 15 of a 28-day cycle. Ki-67 values were evaluated in both biopsy and excision specimens. The clinical responses to NCT were evaluated based on MRI and ultrasound examinations in accordance with the response evaluation criteria in solid tumors (RECIST) version 1.1. The pathological evaluation of surgical specimens was conducted at by the Miller-Payne (MP) grading system. Logistic regression analysis was performed to identify independent predictors of pathological complete response (pCR). Survival analysis was performed to evaluate the prognostic value of various clinical and pathological variables. Results: The overall pCR rate was 33.9%. Both the categorical and linear Ki-67 were independently correlated with pCR (P<0.001). There were also statistically significant differences among Ki-67 categories with respect to clinical response (P<0.001), Miller-Payne (MP) grades (P<0.001), and node status (P<0.001). A significant reduction of Ki-67 after NCT was most likely observed in patients with a relatively better response. Among 185 patients with a residual tumor after NCT, the tumor cell proliferation significantly decreased from a median Ki-67 value of 20.0% before chemotherapy to 15% after chemotherapy. The mean absolute reductions in Ki-67 were 29.4%, 8.5%, and -10.2% in patients with an ideal response (MP 5/4), a partial response (MP 3) and a poor response (MP2/1), respectively. In the multivariate model for non-pCR patients, Ki-67 reduction presented an independent prognostic value for relapse of disease (HR=0.986, 95% CI: 0.978-0.994; P=0.001). Residual node involvement was also an independent predictor of patient outcome (HR=0.895, 95% CI: 0.355-2.259 for 1-3 nodes and HR=2.424, 95% CI: 1.048-5.608 for more than 4 nodes, using 0 nodes as a reference; P=0.002). Better survival was more frequently observed in patients with a greater reduction in the Ki-67 value and fewer involved nodes. Conclusions: The primary Ki-67 might help in further classifying TNBCs into subtypes with different responses to chemotherapy. The significant reduction of Ki-67 after treatment could indicate a favorable prognosis in non-pCR patients. Citation Format: Wang R-X, Chen S, Jin X, Shao Z-M. Predictive and prognostic value of Ki-67 expression in triple-negative breast cancer before and after neoadjuvant chemotherapy with weekly paclitaxel plus carboplatin [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-16-13.