MAGNETIC RESONANCE IMAGING AFTER ADMINISTRATION OF FERUMOXTRAN-10 FOR EVALUATION OF PARAAORTIC LYMPH NODE METASTATASIS IN PATIENTS WITH PANCREATIC CANCER

Abstract

Background: Presence or absence of paraaortic lymph node metastasis is one of the most critical factors to decide indication for surgical resection of pancreatic cancer. However, conventional imaging studies such as computed tomography (CT) and magnetic resonace imaging (MRI) often fail to make a correct diagnosis of paraaortic lymph node metastasis, because paraaortic lymph nodes can be enlarged even without metastasis and because size criteria alone is not good enough to discriminate metastatic lymph nodes from non-metastatic lymph nodes with nonspecific enlargement. Therefore, we have evaluated the paraaortic lymph nodes in six patients with pancreatic cancer by MRI after administration of ferumoxtran-10 (Combidex, Advanced Magnetics, Cambridge, MA), a dextran-coated ultrasmall superparamagnetic iron oxide particle that functions as a contrast agent for lymphatic tissue. Patients and Methods: Six patients with pancreatic cancer who were scheduled for surgical resection were enrolled. All patients underwent MRI scanning 24 hours after the intravenous administration of ferumoxtran-10 as well as multi-detector CT scanning. The presence or absence of metastasis in lymph nodes was assessed on the basis of their enhancement patterns. Briefly, non-malignant nodes contain macrophages that phagocytosed ferumoxtran-10 while, due to a decrease in phagocytic activity, metastaic nodes exhibit little or no uptake of ferumoxtran-10. As a consequence, negative nodes show low signal intensity and positive nodes show partial or entire high signal intensity. The results of MRIafter ferumoctran-10 administartion were compared with those of MD-CT and with the final histopathologic diagnosis. Results: In five of the six patients, surgical resctions either by pancreaticoduodenectomy or distal pancreatectomy were carried out. Histopathologic diagnosis of the paraaortic lymph nodes was all negative for metastasis in these patients. In contrast, intraoperative histopathological study of frozen sections resulted in a diagnsosis of metastasis to paraaortic lymph nodes and by-pass operation was performed in the remining one patient. Sensitivity, specificity, and accuracy of MD-CT were 100%, 25%, and 50%, respectively when enlarged paraaortic lymph nodes > 5 mm were considered positive. Sensitivity, specificity, and accuracy of MRI after ferumoxtran-10 infusion were all 100%. Conclusions: MRI after intravenous administration of ferumoxtran-10 is useful for evaluation of paraaortic lymph node metastasis in patients with pancreatic cancer.