Age and HER2 expression status affect the accuracy of preoperative MRI in predicting tumor extent after neoadjuvant chemotherapy.
Authors: Moon H , Yu J , Kim E , Ko E , Lee J , Han W , Noh D 
Published: December 2010

Abstract #5108

Introduction: Neoadjuvant chemotherapy (NAC) can increase the breast conservation rate and provides prognostic information by identifying patients with pathologic complete remission (pCR). While breast conservation can be safely done in patients who show response to NAC, the presence of chemotherapy-induced fibrosis and the heterogeneous patterns of tumor shrinkage may mislead the determination of residual tumor extent during breast conserving surgery. Recent reports show improved preoperative assessment of residual tumor extent after NAC by performing preoperative breast magnetic resonance imagining (MRI) when compared to conventional methods. In this study, we evaluated the accuracy of preoperative breast MRI in predicting residual tumor extent in patients who underwent NAC, and investigated the factors which may influence its accuracy in a relatively large cohort of patients.&#x2028; Materials and Methods: From Jan 2006 to Feb 2008, 195 non-metastatic breast cancer patients received NAC and surgery in Department of Surgery, Seoul National University Hospital. In all patients, preoperative breast MRI was performed in addition to physical examination, mammography, and ultrasonography (USG) to estimate the residual tumor extent. The results were compared to pathologic tumor sizes, and the accuracy of MRI was determined by simple regression analysis. By using the results of immunohistochemical staining, patients were divided into molecular subtypes, and the accuracy of MRI was compared between each subtypes. To identify a subgroup of patients who might benefit from preoperative MRI, the association of MRI accuracy and various clinicopathologic features as well as molecular markers were investigated using linear regression analysis.&#x2028; Results: The mean age of the patients was 45.5 (±9.4) and mean pathologic tumor size was 4.9 (±2.1) cm. pCR was achieved in 31 patients (15.8%). Preoperative MRI and USG showed similar correlation with pathologic invasive tumor size measured from resected specimens (Pearson Coefficient of 0.492 and 0.462, respectively). However, MRI showed superior correlation with tumor extent when the size of surrounding in situ lesions were taken into consideration (Pearson Coefficient of 0.584 for MRI and 0.495 for USG). MRI showed highest correlation with pathologic tumor size in triple negative subtype and lowest correlation in HER2 subtype. Multivariate analysis showed older age (&gt;45 yrs) and HER2 negativity as independent predictors of MRI accuracy. Mammographic density and initial tumor size did not have significant association with MRI accuracy.&#x2028; Conclusion: Preoprative MRI had high correlation with the extent of residual invasive and in situ tumor size after NAC. The accuracy of MRI was highest in patients with triple negative subtype. Multivariate analysis suggested age and CerbB2 expression as independent predictors of MRI accuracy. Although our results need further validation in a prospective setting, this results may provide a basis for selecting patients in whom the benefit of MRI can be maximized.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5108.