SPIO Enhanced MR Imaging for the Detection of Metastases in Sentinel Nodes Localized by CT Lymphography in Patients with Breast Cancer.

Abstract

Abstract Background: Ultrasonography, magnetic resonance (MR) imaging, and computed tomography (CT) may detect nodal metastases in patients with breast cancer, but there is not sufficient accuracy with the conventional methods. Recently, superparamagnetic nanoparticles-enhanced 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 CT lymphography in patients with breast cancer. This study evaluated MR imaging with superparamagnetic iron oxide (SPIO) enhancement for the detection of metastases in sentinel nodes localized by CT lymphography in patients with breast cancer, with histopathologic findings as the reference standard.Methods: This study included 102 patients with breast cancer with clinically negative nodes. Each contrast agent was injected intradermally into the skin overlying the breast tumor and in the subareolar region. Sentinel nodes were identified by CT lymphography, and SPIO-enhanced MR imaging of the axilla was performed to detect metastases in the sentinel nodes. 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 node biopsy was performed using a combination of dye and radiocolloid. Imaging results were correlated with histopathologic findings.Results: The mean number of sentinel nodes identified by CT lymphography was 1.1 (range 1–3). Twenty-one of 25 patients with positive sentinel nodes definitively diagnosed by pathology demonstrated metastases on SPIO-enhanced MR imaging. Seventy of 77 patients with negative sentinel nodes definitively diagnosed by pathology were non-metastatic on imaging studies. The sensitivity, specificity, and overall accuracy of MR imaging for the diagnosis of sentinel node metastases were 84%, 91%, and 89%, respectively. In four of 10 patients with micrometastases, the metastases were not detected, but all 15 patients with macrometastases were successfully demonstrated. There were no adverse events associated with either CT or MR imaging.Conclusions: SPIO-enhanced MR imaging is a useful method of detecting metastases in sentinel nodes localized by CT lymphography in patients with breast cancer. Patients with clinically negative nodes may be spared sentinel node biopsy when the sentinel node is diagnosed as disease-free using SPIO-enhanced MR imaging. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1010.