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FDG-PET Can Help Differentiate Benign From Malignant Compression Fractures

May 28, 2009
Written by: , Filed in: Emergency Radiology
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Differentiating benign from malignant compression fractures can be challenging, especially in elderly patients. CT and MRI are usually used for assessment, but the diagnosis is sometimes equivalent.

FDG-PET yields metabolic information of tissues, which may allow differentiation between benign and malignant compression fractures.

A recent study set out to evaluate FDG-PET for differentiating benign from malignant compression fractures.

The study has shown that FDG-PET is helpful in differentiating benign from malignant compression fractures, and can be a problem solver in cases of equivocal CT or MRI findings.

The Study/Methodology
In this retrospective review, semiquantitative and qualitative analyses of FDG uptake was performed in 33 patients, and maximum standard uptake values (SUVs) were generated, with lesions >3.0 being considered malignant and <3.0 benign. Lesions between 2.0 and 3.0 were indeterminate and the uptake pattern was factored in.

Results of the Study
There were 33 patients with 43 compression fractures. In total, 29 patients had a history of malignancy; the remainder of patients had FDG-PET for workup of indeterminate lung nodules.

Nine patients had CT and 14 patients had MRI of the spine within 4 weeks of the FDG-PET. Seventeen patients had serial FDG-PET exams.

Nine patients had biopsies and the remainder were followed clinically with repeat imaging studies.

Of 9 biopsies, 3 were benign and 6 were malignant compression fractures.

Emergency Radiology The University of Washington School of Medicine, Harborview Medical Center, Department of Radiology * Features case-based presentations with extensive explanations – 15 hours of video * What, when, and how of imaging in relation to specific topics in emergency medicine * Stresses the interaction and communication required to be an effective part of the emergency medicine team * Provides guidance in diagnosis of polytrauma, commonly missed diagnoses, and when to change existing protocols Click here to read more or order: Emergency Radiology

Of 24 followed patients, 6 were thought to have malignant compression fractures and 18 were thought to have benign results.

Five fractures were acute and benign. On visual inspection, 26 fractures on FDG-PET were benign and 17 were malignant. Uptake was intense for malignant fractures, while benign compression fractures showed only mildly or no increased uptake.

FDG-PET characterized 12 lesions correctly as malignant and 24 as benign. There were 2 false-negative cases (uptake moderately increased, with SUVs 2.5 and 2.8) and 5 false-positive cases. Three false-positive cases were on marrow-stimulating drugs.

Quantitative analysis demonstrated the SUVs for benign fractures ranging from 0.7 to 4.9 (mean 1.94 +/- 0.97) and for malignant fractures 2.2 to 7.1 (mean 3.99 +/- 1.52). This difference was statistically significant (P <0.001). Sensitivity, specificity, positive- and negative-predictive values, and accuracy were 86%, 83%, 84%, 71%, and 92%, respectively.

Conclusions
FDG-PET is helpful in differentiating benign from malignant compression fractures, and can be a problem solver in cases of equivocal CT or MRI findings.

Reviewer’s Comments

Limiting factors in this study were the retrospective nature and lack of cases with infection, which can mimic malignancies.

However, investigators were blinded to clinical history and data, therefore misinterpreting patients on marrow-stimulating drugs. This information is usually available, eliminating some of the false-positive cases.

Author: Cornelia Wenokor, MD

Reference:
Bredella MA, Essary B, et al. Use of FDG-PET in Differentiating Benign From Malignant Compression Fractures. Skeletal Radiol; 2008; 37 (May): 405-413

Emergency Radiology The University of Washington School of Medicine, Harborview Medical Center, Department of Radiology * Features case-based presentations with extensive explanations – 15 hours of video * What, when, and how of imaging in relation to specific topics in emergency medicine * Stresses the interaction and communication required to be an effective part of the emergency medicine team * Provides guidance in diagnosis of polytrauma, commonly missed diagnoses, and when to change existing protocols Click here to read more or order: Emergency Radiology
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