SPIO-enhanced magnetic resonance imaging for the detection of metastases in sentinel nodes localized by computed tomography lymphography in patients with breast cancer.

Background: Superparamagnetic nanoparticle-enhanced magnetic resonance (MR) imaging has been reported to be a promising improvement for diagnostic imaging of lymph node metastases from various tumors. Moreover, sentinel nodes have been reported to be well identified using computed tomography (CT) lymphography (CT-LG) in patients with breast cancer. The aim of this study was to evaluate MR imaging with superparamagnetic iron oxide (SPIO) enhancement for the detection of metastases in sentinel nodes localized by CT-LG in patients with breast cancer.
Methods: This study included 102 patients with breast cancer and clinically negative nodes. Sentinel nodes were identified by CT-LG, and SPIO-enhanced MR imaging of the axilla was performed to detect metastases in the sentinel nodes. A node was considered nonmetastatic if it showed a homogenous low signal intensity and metastatic if the entire node or a focal area did not show low signal intensity on MR imaging. Sentinel node biopsy was performed, and imaging results were correlated with histopathologic findings.
Results: The mean number of sentinel nodes identified by CT-LG was 1.1 (range, 1-3). The sensitivity, specificity, and accuracy of MR imaging for the diagnosis of sentinel node metastases were 84.0%, 90.9%, and 89.2%, respectively. In 4 of 10 patients with micrometastases, metastases were not detected, but all 15 patients with macrometastases were successfully identified.
Conclusions: SPIO-enhanced MR imaging is a useful method of detecting metastases in sentinel nodes localized by CT-LG in patients with breast cancer and may avoid sentinel node biopsy when the sentinel node is diagnosed as disease-free.