Objective: The purpose of this study was to administer ultrasmall superparamagnetic iron oxide (USPIO) and compare changes in signal intensity of lymph nodes in patients with primary abdominal and pelvic malignancies. Also, we correlated radiographic with pathologic findings.
Subjects and methods: Nineteen patients with proven primary abdominal or pelvic cancer (prostatic [n = 10]; colonic [n = 5]; endometrial [n = 1]; Merkel cell tumor [n = 1]; lymphoma [n = 1]; seminoma [n = 1]) were enrolled as part of our phase II and phase III clinical trials. In these patients, 49 lymph nodes (mean size, 1.4 cm) revealed on CT or MR imaging were evaluated on T1-weighted spin-echo, T2-weighted fast spin-echo, and T2*-weighted gradient-echo MR imaging at 1.5 T 24-36 hr after IV administration of USPIO. Quantitative analyses used measurements of unenhanced and enhanced region-of-interest values in lymph nodes. Qualitative assessment used subjective evaluation and classification of changes in signal intensity. All patients underwent lymph node biopsy or surgical dissection followed by histopathologic correlation.
Results: Of the 49 lymph nodes that were evaluated, 20 were benign and 29 were malignant. A decrease in nodal signal intensity on enhanced T2-weighted and T2*-weighted gradient-echo images was seen in 20 benign lymph nodes and two malignant lymph nodes. No appreciable signal change was noted in 27 of the 29 malignant lymph nodes. The mean signal intensity on fast spin-echo T2-weighted images for benign lymph nodes changed from 186.48 (unenhanced) to 73.66 (enhanced). Conversely, mean signal intensity for malignant lymph nodes was relatively unchanged from 191.17 (unenhanced) to 183.18 (enhanced).
Conclusion: USPIO appears to be a useful MR contrast agent for characterizing benign and malignant lymph nodes based on the enhancement criteria evaluated in our study.