http://www.medscape.com/viewarticle/508400


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Mangafodipir Trisodium-Enhanced MRI, Whole-Body FDG-PET Comparable in
Detecting Patients With Liver Metastases


Laurie Barclay, MD;
Medscape Medical News 2005. © 2005 Medscape




July 18, 2005 — In patients with colon and pancreatic adenocarcinoma,
liver magnetic resonance imaging (MRI) with mangafodipir trisodium
enhancement provides more detail of liver metastases, whereas whole-
body fluorodeoxyglucose positron emission tomography (FDG-PET) may
offer additional information regarding extrahepatic disease,
according to the results of a study published in the July issue of
the American Journal of Roentgenology.

"MRI has been shown to be equal in sensitivity and specificity to
[computed tomography] CT arterioportography in the detection of focal
liver lesions," write Dushyant V. Sahani, MD, from Massachusetts
General Hospital in Boston, and colleagues. "PET with fluorine-18 FDG
is established as an important method for staging gastrointestinal
malignancies. A limited number of publications have directly compared
MRI and FDG-PET for the detection of liver metastases."

The investigators retrospectively reviewed imaging data of 34
patients who had undergone mangafodipir trisodium-enhanced liver MRI
and whole-body FDG-PET for the presence and number of liver
metastases. Age range was 44 to 78 years. There were 23 men and 11
women; and 27 patients had adenocarcinoma of the colon whereas seven
had adenocarcinoma of the pancreas. The standard of reference was
histopathology in 25 patients and follow-up imaging in nine patients.

Breathhold T1-weighted gradient-recalled echo, respiratory-triggered
T2-weighted fast spin-echo, and mangafodipir trisodium--enhanced
axial fat-saturated high-spatial-resolution (256 × 512) T1-weighted
gradient-recalled echo images were obtained on a 1.5-T scanner, and
FDG-PET was performed after the injection of 15-20 mCi (555-740 MBq)
FDG.

Based on the gold standard, 30 patients had a total of 79 hepatic
metastases, including 33 lesions that measured less than 1 cm, and
four patients had no hepatic metastases. Per-patient analysis yielded
sensitivities of 96.6% for MRI and 93.3% for FDG-PET, positive
predictive values of 100% and 90.3%, and accuracies of 97.1% and
85.3%, respectively.

Per-lesion analysis revealed sensitivities of 81.4% and 67.0%,
positive predictive values of 89.8% and 81.3%, and accuracies of
75.5% and 64.1%, respectively. MRI detected more hepatic metastases
than did FDG-PET (P = .016), and MRI detected all of the 33 confirmed
subcentimeter lesions, whereas only 12 were detected on FDG-PET (P
= .0001).

"In patients with colon and pancreatic adenocarcinoma, high-spatial-
resolution mangafodipir trisodium-enhanced liver MRI and whole-body
FDG-PET were comparable in the detection of patients with liver
metastases," the authors write. "FDG-PET provided additional
information about extrahepatic disease and was useful in initial
staging. However, significantly more and smaller liver metastases
were detected on MRI than on FDG-PET."

Study limitations include the retrospective nature of the data
collection and analysis, which may introduce inadvertent bias; lack
of histopathologic confirmation in nine patients; inclusion of only
patients who underwent liver MRI, whole-body FDG-PET, and surgery or
followup imaging within six weeks; and inability to determine the
impact on treatment strategy or survival benefit for patients in whom
additional lesions were detected or missed with either technique.

"In patients being considered for liver resection after initial
staging for metastatic disease, the treatment decision should be
based primarily on liver MRI because additional lesions detected on
MRI may alter or preclude such surgery," the authors conclude.

Am J Roentgenol. 2005;185:239-246

Reviewed by Gary D. Vogin, MD


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