SPIO-enhanced MR imaging at 3T for accurate diagnosis of sentinel node metastases to avoid sentinel node biopsy in patients with breast cancer.

Abstract

68 Background: We previously demonstrated the usefulness of SPIO-enhanced MR imaging at 1.5T for the detection of metastases in sentinel nodes identified 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 whether SPIO-enhanced MR imaging at 3T improved the diagnostic accuracy for the detection of metastases in sentinel nodes. Moreover, these results were compared with those of the diagnosis using CT-LG according to the size criteria. Methods: Seventy patients with breast cancer and clinically negative nodes were included. Sentinel nodes identified by CT-LG were evaluated prospectively using SPIO-enhanced MR imaging at 3T. Sentinel node size was measured on CT-LG and a node larger than 5 mm in short axis diameter was considered metastatic. Sentinel nodes localized by CT-LG were removed, and imaging results and histopathological findings were compared. Results: The mean patient age was 55 years (range, 29-78). Sentinel nodes were identified by CT-LG successfully in 69 (98.6%) of 70 patients. The mean number of sentinel nodes identified by CT-LG was 1.4 (range, 1-3). All 19 patients with positive sentinel nodes definitively diagnosed by pathology demonstrated metastases on SPIO-enhanced MR imaging. Forty-eight of 50 patients with negative sentinel nodes definitively diagnosed by pathology were non-metastatic on the imaging studies. The sensitivity, specificity and accuracy of MR imaging for the diagnosis of sentinel node metastases were 100%, 96.0%, and 97.1%, respectively, on a patient-by-patient basis. Those of CT-LG were 78.9%, 56.0%, 62.3%, respectively. The specificity and accuracy of MR imaging were superior to those of CT-LG (McNemar test; p < .0001 and = .0015, respectively). Conclusions: SPIO-enhanced MR imaging at 3T can accurately diagnose the sentinel node metastases, and therefore sentinel node biopsy may not be required for most patients with breast cancer.