Preoperative breast cancer staging:: MR imaging of the axilla with ultrasmall superparamagnetic iron oxide enhancement

PURPOSE: To evaluate, Magnetic resonance (MR) imaging with ultrasmall superparamagnetic iron oxide. (USPIO) enhancement for preoperative axillary lymph node staging in patients with breast cancer by using histopathologic findings as the standard of reference. MATERIALS AND METHODS: MR imaging was performed with a 1.5-T system within 24-36 hours after the start of intravenous slow-drip infusion of USPIO in 20 patients with breast cancer who were scheduled for surgery, followed by gadolinium-enhanced MR imaging, Lymph nodes were staged prospectively by using newly established criteria, and results were correlated with histologic findings. RESULTS: In two patients, preoperative findings led to a change in therapeutic approach, and neoadjuvant chemotherapy was given; both patients were excluded from statistical analysis. Results of axillary staging with USPIO-enhanced MR imaging were true-positive in nine, I true-negative in seven, false-positive in zero, and false-negative in two of 18, patients (sensitivity, 82%; specificity, 100%; positive predictive value 100%; second reader, K = 1.0). Four hundred five lymph nodes were detected kith MR imaging. For first and second readers, respectively, lymph node-based sensitivity was, 83% and 73% and specificity was 96% and 97% (K 0.68). USPIO as the intravascular contrast agent could not replace gadolinium for assessment of the primary tumor; however, no clinically relevant interaction was seen. Thus, an integrated, imaging approach was feasible in all patients. CONCLUSION: USPIO-enhanced MR imaging has the potential to become an adjunct to conventional,MR imaging of the breast for preoperative assessment of axillary lymph nodes in patients with breast cancer. (C) RSNA, 2002.