SPIO-enhanced MR imaging at 3T for the detection of metastases in sentinel nodes in patients with breast cancer.

1107 Background: We previously demonstrated the usefulness of SPIO-enhanced MR imaging at 1.5T for the detection of metastases in sentinel nodes localized by computed tomography lymphography (CT-LG) in patients with breast cancer (Ann Surg Oncol 2011, ASCO 2012). The aim of this study was to evaluate the accuracy of MR imaging at 3T with SPIO enhancement for the detection of metastases in sentinel nodes. Methods: This study included 60 patients with breast cancer and clinically negative nodes. Sentinel nodes identified by CT-LG were evaluated prospectively using SPIO-enhanced MR imaging at 3T. A node was considered non-metastatic if it showed a homogenous low signal intensity and metastatic if the entire node or a focal area did not show a low signal intensity on MR imaging. Sentinel nodes located by CT-LG were removed, and imaging results and histopathological findings were compared. Results: The mean patient age was 54.2 years (range, 33-78). Sentinel nodes were identified by CT-LG successfully in 59 (98.3%) of 60 patients. The mean number of sentinel nodes identified by CT-LG was 1.43 (range, 1-3). All 16 patients with positive sentinel nodes definitively diagnosed by pathology demonstrated metastases on SPIO-enhanced MR imaging. Five (31.3%) of them had micrometastases. Forty-one of 43 patients with negative sentinel nodes definitively diagnosed by pathology were non-metastatic on imaging studies. The sensitivity, specificity and accuracy of MR imaging for the diagnosis of sentinel node metastases were 100%, 95.3%, and 96.6%, respectively. No adverse events were associated with either CT or MR imaging. Conclusions: SPIO-enhanced MR imaging at 3T is useful for accurate diagnosis of sentinel node metastases, and therefore sentinel node biopsy may be avoided for most patients with breast cancer.