Abstract
PurposeTo evaluate the initial results of predicting lymph node metastasis in rectal cancer patients detected in-vivo with USPIO-enhanced MRI at 3 T compared on a node-to-node basis with histopathology. MethodsTen rectal cancer patients of all clinical stages were prospectively included for an in-vivo 0.85 mm3 isotropic 3D MRI after infusion of Ferumoxtran-10. The surgical specimens were examined ex-vivo with an 0.29 mm3 isotropic MRI examination. Two radiologists evaluated in-vivo MR images with a classification scheme to predict lymph node status. Ex-vivo MRI was used for MR-guided pathology and served as a key link between in-vivo MRI and final histopathology for the node-to-node analysis. Results138 lymph nodes were detected by reader 1 and 255 by reader 2 (p = 0.005) on in-vivo MRI with a median size of 2.6 and 2.4 mm, respectively. Lymph nodes were classified with substantial inter-reader agreement (κ = 0.73). Node-to-node comparison was possible for 55 lymph nodes (median size 3.2 mm; range 1.2–12.3), of which 6 were metastatic on pathology. Low true-positive rates (3/26, 11 % for both readers) and high true negative rates were achieved (14/17, 82 %; 19/22, 86 %). Pathological re-evaluations of 20 lymph nodes with high signal intensity on USPIO-enhanced MRI without lymph node metastases (false positives) did not reveal tumor metastasis but showed benign lymph node tissue with reactive follicles. ConclusionsHigh resolution MRI visualizes a large number of mesorectal lymph nodes. USPIO-enhanced MRI was not accurate for characterizing small benign versus small tumoral lymph nodes in rectal cancer patients. Suspicious nodes on in-vivo MRI occur as inflammatory as well as metastatic nodes.
Highlights
The presence of lymph node metastases in rectal cancer is a key factor in determining prognosis and treatment [1]
Of whom 2 female and 8 male patients with a mean age of 64 years (SD 7.7). 5 patients were scheduled for total mesorectal excision (TME) surgery only and 5 patients for neoadjuvant chemoradiotherapy (nCRT) fol lowed by TME
The current study showed the first results of 3D ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI on a 3 T MR-system
Summary
The presence of lymph node metastases in rectal cancer is a key factor in determining prognosis and treatment [1]. Diagnostic lymph node staging, is still a major challenge [2,3,4]. Over the past decade multiple imaging approaches have been assessed as a biomarker to differentiate between benign and malignant lymph nodes [5,6,7,8,9,10]. Variation in interpreting MR images leads to predominantly upstaging with potential effects on treatment [4,13]. There is a need for a more accurate pre diction of the presence of lymph node metastases
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