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IMAGING
Utility
of PET/CT in differentiating benign from malignant adrenal nodules in
patients with cancer
Vikram R, Yeung HD, Macapinlac HA, Iyer RB
Department of Diagnostic Radiology, The University of Texas M.D. Anderson
Cancer Center, Houston, TX, USA
AJR Am J Roentgenol. 2008; 191: 1545-51
- Objective:
The
purpose of this retrospective study was to determine the sensitivity
and specificity of combined PET/CT in differentiating benign from malignant
adrenal nodules measuring at least 1 cm in diameter in patients with
cancer.
-
Materials and Methods: We
reviewed the radiology reports and images of patients with known malignant
disease who had undergone PET/CT for cancer staging or surveillance
and who had adrenal nodules at least 1 cm in diameter. We identified
112 adrenal nodules in 96 patients. Two-dimensional PET had been performed
1 hour after administration of (18)F-FDG. Unenhanced CT was performed
for attenuation correction, to determine lesion size, and for coregistration
with PET data. Adrenal nodules were considered to have a positive PET
result if the average standardized uptake value was greater than that
of the liver. Follow-up data and biopsy reports were used to determine
the pathologic status of the adrenal nodules.
-
Results:
Thirty adrenal lesions were malignant. Twenty-five of the 30 malignant
nodules had positive PET results. Twelve of 82 benign nodules were PET
positive with a sensitivity of 83.3% and specificity of 85.4%. Patients
with four of five malignant nodules with negative PET results had received
previous therapy. The positive predictive value for detection of malignant
lesions was 67%, and the negative predictive value was 93%.
-
Conclusion:
Adrenal masses that are not FDG avid are likely to be benign with a
high negative predictive value. Especially in patients undergoing therapy,
however, there is a small but statistically significant false-negative
rate. A considerable proportion of benign nodules have increased FDG
activity.
- Editorial
Comment
Accurate characterization of most adrenal lesions is usually obtained
with either CT or MRI. The use of standard CT techniques (unenhanced
CT attenuation and CT washouts-absolute percentage) isolated or combined
with MRI techniques (“chemical shift imaging”, diffusion-weighted
images and 3D-spectroscopy) are usually sufficient for the differentiation
between benign and malignant lesion in the vast majority of adrenal
nodules. Nuclear medicine studies prove to be useful adjuncts. Controversial
reports have been published on the role of PET/CT in this clinical and
radiologic setting because some adrenal adenomas and in?ammatory / infectious
lesions demonstrate slight increased radiotracer uptake. Similarly,
necrotic or hemorrhagic malignant adrenal lesions occasionally may cause
false-negative results.
The authors of this manuscript show that although with these few limitations
PET/CT is useful for characterizing adrenal nodules. In our opinion,
PET/CT should be used whenever CT and / or MRI techniques are not diagnostic.
One important point to consider is that all these imaging techniques
are complimentary and thus can be associated since they use fundamentally
different biologic principles. Following this simplified algorithm,
the use of image-guided adrenal biopsy will be in the near future used
only in those rare patients where adrenal lesions remain indeterminate
after CT, MRI and PET/CT techniques.
Dr.
Adilson Prando
Chief, Department of Radiology and
Diagnostic Imaging, Vera Cruz Hospital
Campinas, São Paulo, Brazil
E-mail: adilson.prando@gmail.com |