PET/CT shows promise
as first-line tool for oncologic staging, topping MRI in one head-to-head
comparison
By Jonathan S. Batchelor
December 3, 2003
CHICAGO - Accurate
tumor staging is critical for patient management in clinical oncology. Research
conducted by a team from Essen, Germany,
suggests stage-adapted therapy – tumor staging (T), lymph node metastasis
staging (N), and distant metastasis staging (M) – may benefit by the use of a
mix of modalities.
Dr. Gerald Antoch, from the department of radiology at the
University Hospital of Essen, presented the results of a study performed to
compare the diagnostic accuracy of whole-body dual-modality PET/CT with
whole-body MRI for the staging of cancer at the RSNA 2003 on Tuesday.
The researchers conducted imaging studies with PET/CT and MRI on patients with
different malignant diseases to assess tumor staging. The studies all covered
an axial field of view from the head to the upper thighs, said Antoch
The team imaged 60 patients using a dual-modality PET/CT (Biograph,
Siemens
Medical Solutions). PET
imaging was performed one hour after the administration of 18-FDG and both intravenous and oral contrast agents
were used in the diagnostic CT portion of the scan, he said.
MRI imaging was conducted on a 1.5 T scanner (Sonata,
Siemens Medical Solutions). Unenhanced T1- and T2-weighted studies of the liver
and thorax as well as contrast-enhanced whole-body T1 coverage was conducted by
the team. PET/CT and MRI data sets were evaluated by different reader teams who
were blinded to the results of the other imaging procedure, reported Antoch.
The researchers used histological results and clinical
follow-up (mean, 199 days, +/-68) as their standards of
reference.
“We limited our whole-body modality-to-modality comparison
of accurate T-staging with PET/CT and MRI to 47 patients whose tumor stage was
histologically verified,” noted Antoch. The group found that the T-stage was
accurately determined in 41 of 47 patients (87%) with PET/CT and in 28 of 47
patients with MRI (60%).
PET/CT accurately staged lymph node status in
92 of 99 patients (93%) while MRI had a correct N-status in 82 of 99 patients
(83%), according to the researchers. The M-stage was correctly determined in 91
of 99 patients (92%) with PET/CT and in 90 of 99 patients (91%) with MRI, said
Antoch.
However, when the researchers looked at specific sites of
carcinoma, both MR and PET/CT showed staging strengths and weaknesses. Antoch
reported that PET/CT was superior in the staging of pulmonary metastases with sensitivity
and specificity both at 96%, compared with MRI’s 89%
and 81%.
Although PET/CT showed strong numbers for staging liver
metastases, a sensitivity and specificity of 90% and 98%, MRI was more accurate
with a sensitivity of 100% and a specificity of 97%. Bone metastases were also
better staged with MRI, with PET/CT demonstrating a sensitivity of 75% and a
specificity of 97%, while MRI showed an 83%
sensitivity and a 96% specificity, he said.
“When it comes to whole-body imaging for the purposes of
determining the T and N stage of tumors, PET/CT demonstrates better sensitivity
and specificity than MRI. However, for certain metastases, such as those in the
liver and bone, MRI is the superior imaging tool. On the basis of our results,
we believe that PET/CT is ready to be used as a first-line tool for oncologic
staging,” said Antoch.
By Jonathan S.
Batchelor
AuntMinnie.com staff writer
December 3, 2003
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