SPIO-enhanced MR imaging for axillary staging to avoid sentinel node biopsy in patients with breast cancer.

1103 Background: We previously demonstrated the usefulness of SPIO-enhanced MR imaging for the detection of metastases in sentinel nodes localized by computed tomography (CT) lymphography (CT-LG) in patients with breast cancer (Ann Surg Oncol, 2011). These techniques have evolved and we report our most recent results of axillary staging using them. Methods: Previously unreported 87 consecutive patients with breast cancer and clinically negative nodes were enrolled in this study. Sentinel nodes identified by CT-LG were evaluated prospectively using SPIO-enhanced MR imaging. 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 54.9 years (range, 34-77). Sentinel nodes were identified by CT-LG and removed successfully in all patients. The mean number of sentinel nodes identified by CT-LG was 1.16 (range, 1-2). Twenty of 22 patients with positive sentinel nodes definitively diagnosed by pathology demonstrated metastases on SPIO-enhanced MR imaging. Fifty-eight of 65 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 91%, 89%, and 90%, respectively. Two patients whose metastases were not detected had micrometastases. No adverse events were associated with either CT or MR imaging. Conclusions: SPIO-enhanced MR imaging provided accurate axillary staging, and therefore sentinel node biopsy may not be necessary for most patients with breast cancer.