Diagnostic accuracy of nodal enhancement pattern of rectal cancer at MRI enhanced with ultrasmall superparamagnetic iron oxide: findings in pathologically matched mesorectal lymph nodes.
OBJECTIVE
The purpose of this study was to evaluate the diagnostic accuracy of the pattern of nodal enhancement at MRI enhanced with ultrasmall superparamagnetic iron oxide (USPIO) in the nodal classification of rectal cancer in pathologically matched mesorectal lymph nodes.


METHODS
Twenty-five patients with adenocarcinoma of the rectum underwent prospective evaluation with 3-mm axial T2-weighted and USPIO-enhanced T2*-weighted MRI before surgery. Mesorectal nodes visible at in vivo MRI were independently scored by two radiologists as malignant or nonmalignant according to morphologic criteria (irregular nodal contour, heterogeneous signal intensity) on T2-weighted MR images and according to USPIO enhancement pattern on T2*-weighted MR images. The sensitivity, specificity, and positive and negative predictive values of morphologic and USPIO criteria in identification of malignancy in the pathologically matched mesorectal nodes were compared by use of the McNemar test. Interobserver agreement was compared by use of kappa statistics.


RESULTS
After surgery, radiologic-pathologic comparison of 126 mesorectal nodes (116 benign, 10 malignant) was possible. Use of morphologic criteria resulted in an average sensitivity of 65% (95% CI, 35-88%); specificity, 75% (67-83%); positive predictive value, 19% (8-34%); and negative predictive value, 96% (91-99%). Use of USPIO criteria resulted in an average sensitivity of 65% (95% CI, 35-88%); specificity, 93% (87-96%); positive predictive value, 43% (21-67%); and negative predictive value, 97% (92-99%). Use of USPIO MRI improved diagnostic specificity for both observers (p < 0.01). Interobserver agreement was fair for morphologic criteria (kappa = 0.39) but good for USPIO criteria (kappa = 0.68).


CONCLUSIONS
Use of the pattern of USPIO enhancement had higher diagnostic specificity than but the same sensitivity as morphologic findings in pathologically matched mesorectal lymph nodes.
Koh
Dow-Mu
DM
Department of Radiology, Royal Marsden Hospital, Sutton, Surrey SM2 5PT, United Kingdom.
George
Christopher
C
Temple
Louis
L
Collins
David J
DJ
Toomey
Paul
P
Raja
Ashraf
A
Bett
Nicholas
N
Farhat
Sami
S
Husband
Janet E
JE
Brown
Gina
G
D000230:Adenocarcinoma / Q000473:pathology*; D000368:Aged; D003287:Contrast Media; D003911:Dextrans; D005260:Female; D052203:Ferrosoferric Oxide; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008207:Lymphatic Metastasis / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D012004:Rectal Neoplasms / Q000473:pathology*; D012680:Sensitivity and Specificity
D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; C097921:ferumoxtran-10; D052203:Ferrosoferric Oxide