Predictive Factors Of Pathologic Complete Response Of Her2-Positive Breast Cancer After Preoperative Chemotherapy With Trastuzumab: Development Of A Specific Predictor

Purpose: The aim of this study was to assess the M.D Anderson Cancer Center / Gustave Roussy Institute (MDACC/IGR) nomogram in predicting pathologic complete response (pCR) to preoperative chemotherapy in a cohort of HER2 tumors treated with preoperative chemotherapy with trastuzumab. Then, we combine clinical and pathological variable associated with pCR into a new nomogram specific of HER2 tumors treated by preoperative chemotherapy with trastuzumab. Methods: Data from 270 patients treated with preoperative chemotherapy with trastuzumab at Curie Institute and at Georges Francois Leclerc Cancer Center were used to assess MDACC/IGR nomogram and then to develop a nomogram for pCR based on multivariate logistic regression. Model performance was quantified with respect to calibration and discrimination. Results: The IGR/MDACC was not accurate to predicting pCR in HER2 tumors treated by preoperative chemotherapy with trastuzumab with poor discrimination (AUC=0,54, IC [0,51-0,58]) and poor calibration (p=0,01). After uni and multivariate analysis, the new pCR nomogram was based on T stage (TNM), hormonal receptor status, and ki67(%). The model had a good discrimination 0,74 (IC95% : [0,70-0,79]) and a good calibration (p=0,93). Conclusion: To our knowledge, this is the first nomogram to predict pCR in HER2 tumors treated by preoperative chemotherapy with trastuzumab. To ensure exportability, the model need to be evaluate with a external validation set. Citation Format: Jankowski C, Guiu S, Cortet M, Hudry D, Arnould L, Charon-Barra C, Desmoulins I, Rouzier R, Fumoleau P, Coudert B, Reyal F, Coutant C. Predictive factors of pathologic complete response of HER2-positive breast cancer after preoperative chemotherapy with trastuzumab: Development of a specific predictor. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-14-21.