P3-07-46: Accuracy of SPIO-Enhanced MR Imaging Alone for the Diagnosis of Sentinel Node Metastases in Patients with Breast Cancer.

Abstract

Abstract Background Superparamagnetic iron oxide (SPIO)-enhanced MR imaging has been reported to be promising for the detection of metastases in sentinel nodes localized by CT lymphography in patients with breast cancer (Motomura, Ann Surg Oncol 2011). The current SPIO technique involves imaging before and after contrast administration. This study evaluated the accuracy of SPIO-enhanced MR imaging alone without unenhanced imaging. Methods: This study included 120 patients with breast cancer demonstrating clinically negative nodes. Sentinel nodes were identified by CT lymphography, and MR imaging of the axilla before and 18–24 hr after interstitial administration of SPIO was performed. A node was considered non-metastatic if it showed a homogenous low signal intensity and metastatic if there was an absence of low signal intensity either in the entire node or in a focal area on SPIO-enhanced MR imaging. The diagnostic accuracy of the SPIO-enhanced imaging alone was compared with that of combined unenhanced and SPIO-enhanced imaging. Results: The mean number of sentinel nodes identified by CT lymphography was 1.2 (range 1–3). Pathologic evaluation demonstrated that 28 (23.3%) of 120 patients showed metastasis to at least one node. One false negative result was added when the evaluation was based solely on SPIO-enhanced MR imaging. Consequently, the sensitivity decreased from 84.0% to 80.0% and the accuracy decreased from 89.2% to 88.3%, respectively, in the SPIO-enhanced MR imaging alone. However, the differences in sensitivity and accuracy between SPIO-enhanced MR imaging alone and the combined unenhanced and SPIO-enhanced imaging were not significant (McNemar's test; p=1.0). The specificity of enhanced imaging alone and that of combined unenhanced and SPIO-enhanced imaging were both 90.5%. Conclusions: A single MR imaging examination performed after SPIO administration can be used for accurate diagnosis of sentinel node metastases, and thus reduce the time and cost of imaging. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-07-46.