Evaluation of lymph node metastases of breast cancer using ultrasmall superparamagnetic iron oxide-enhanced magnetic resonance imaging

BACKGROUND: We assessed the utility of enhanced magnetic resonance imaging (MRI) using ultrasmall superparamagnetic iron oxide (USPIO) in the evaluation of axillary lymph node metastases in patients with breast cancer. STUDY DESIGN: MR examination of the axilla was performed before and 24-36 h after USPIO administration for patients with stage II or III breast cancer. Diagnostic performance was compared using size criteria (metastasis was defined when short axis diameter >5 or >10mm) or morphologic criteria on conventional MRI, the combined study of USPIO precontrast and postcontrast images, and USPIO postcontrast study alone. RESULTS: A total of 622 nodes (503 metastatic and 119 nonmetastatic nodes) were dissected from 33 patients. The results of conventional MRI for nodes >5mm were 59.1% sensitivity, 86.7% specificity, and 80.4% overall accuracy. Results for nodes >10mm were 15.7% sensitivity, 99.2% specificity, and 80.2% overall accuracy. Results based on morphology were 36.5% sensitivity, 94.1% specificity, and 81.0% overall accuracy. The results of the combined study of USPIO precontrast and postcontrast images were 86.4% sensitivity, 97.5% specificity, 91.1% positive predictive value, 96.1% negative predictive value, and 95.0% overall accuracy. The results of USPIO postcontrast images alone were 84.7% sensitivity, 96.8% specificity, and 94.0% overall accuracy. Patient-based results of postcontrast USPIO study alone were 100.0% sensitivity, 80.0% specificity, and 93.9% overall accuracy. CONCLUSIONS: USPIO postcontrast study alone was useful in the assessment of axillary lymph node metastases in patients with breast cancer.