341P - Accuracy of Magnetic Resonance Imaging Prediction of Pathologic Complete Response in Patients with Breast Cancer Treated with Neoadjuvant Chemotherapy

Abstract

ABSTRACT Background: Magnetic Resonance Imaging (MRI) is accepted as the best exploration to predict pathological response to neoadjuvant chemotherapy (NAC) in breast cancer. Our goal is to analyze the correlation between radiological complete response (rCR) and pathological complete response (pCR), globally and according to the different tumor immunophenotypes (IF). Methods: This study included patients with clinical stage I-III who were treated with NAC at our breast cancer unit between January 2006 and December 2012. Patients underwent a baseline MRI and after NAC. The radiological response was assessed according to the RECIST version 1.1 and the pathological response according to the Miller & Payne grading system. Results: A total of 214 patients were included with a mean age of 56.3 years. Concerning clinical stage, 55.1% of the patients were classified as stage II and 40.7% as stage III. Most patients (82.7%) received NAC with anthracyclines and taxanes. Regarding the type of surgery the majority of patients (69.2%) underwent breast conserving surgery. A pCR was achieved in 18.7% patients, 52% in HER2+ tumors, 31.3% in triple-negative (TN), 28.6% in luminal-B-HER2 + , 5.4% in luminal-B-HER2- and 1,4% in luminal-A. The rCR rate was 24.9%. Table 1 reports overall results of MRI accuracy predicting pCR estimating sensitivity (Se) and specificity (Sp), as well as specific results for each immunophenotype. We have analyzed the reliability of MRI to detect complete response in breast and axillary lymph nodes independently, reporting Se of 55,8% and 69.3 % respectively (p = 0,113) and Sp of 81.3% and 41% (p Overall n 214 HER2 + n 29 Luminal A n 71 LuminalB-HER2+ n 29 LuminalB-HER2- n 37 Triple negative n 48 Se (%) 57,6 (23/40) 66,7 (10/15) 0 (0/1) 28,6 (2/7) 100 (2/2) 60 (9/15) Sp (%) 82,8 (144/174) 78,6 (11/14) 78,6 (55/70) 86,3 (19/22) 91,4 (32/35) 81,8 (27/33) Conclusions: MRI achieves Se 57.6% and Sp 82.8% predicting pCR. The values of Se are higher in TN and HER2+ tumors while the values of Sp are higher in Luminal-B and TN tumors. The Sp of MRI for detecting pCR is higher in breast than in axillary lymph nodes. Disclosure: All authors have declared no conflicts of interest.