Can MRI accurately identify which patients with operable breast cancer will have a pathologic complete response after neoadjuvant therapy

616 Background: With the introduction of targeted therapy based on tumor subtypes, an increasing number of patients that receive neoadjuvant chemotherapy achieve a pathologic complete response (pCR). Previous studies have shown that the accuracy of MRI is poor at predicting the response to neoadjuvant chemotherapy in locally advanced and often non-resectable breast cancers, where the rate of pCR is low. The purpose of this study is to evaluate MRI’s ability to predict a pCR in operable breast cancers after neoadjuvant therapy. Methods: All patients enrolled in the NSABP B-40, B-41, FB-5 and FB-6 protocols in a single tertiary care centre, that had an MRI done before and after neoadjuvant therapy were reviewed. A radiologist, blinded to the pathology results, interpreted the pre- and post- treatment MRI’s and made a prediction as to whether or not patients would have a pCR. In this study, a true negative was defined as a reading of a complete response on MRI that was confirmed as a pCR on final pathology. ...