J Nucl Med 2001 May;42(5):713-20
Dynamic pet (18)f-fdg studies in patients with primary and recurrent
soft-tissue sarcomas: impact on diagnosis and correlation with grading.
Dimitrakopoulou-Strauss A, Strauss LG, Schwarzbach M, Burger C, Heichel T,
Willeke F, Mechtersheimer G, Lehnert T.
The purpose of this study was to evaluate (18)F-FDG PET studies of primary and
recurrent sarcomas for diagnosis and correlation with grading. METHODS: The
evaluation included 56 patients, 43 with histologically proven malignancies and
13 with benign lesions. Seventeen patients were referred with suspicion on a
primary tumor, and the remaining 39 were referred with suspicion on a recurrent
tumor. The FDG studies were accomplished as a dynamic series for 60 min. The
evaluation of the FDG kinetics was performed using the following parameters:
standardized uptake value (SUV), global influx, computation of the transport
constants K1-k4 with consideration of the distribution volume (VB) according to
a two-tissue-compartment model, and fractal dimension based on the box-counting
procedure (parameter for the inhomogeneity of the tumors). RESULTS: Visual
evaluation revealed a sensitivity of 76.2%, a specificity of 42.9%, and an
accuracy of 67.9%. The vascular fraction VB and the SUV were higher in malignant
tumors compared with benign lesions (t test, P < 0.05). Although the FDG SUV
helped to distinguish benign and malignant tumors, there was some overlap, which
limited the diagnostic accuracy. The SUV and fractal dimension accounted for
significant differences in six of the nine diagnostic pairs. Whereas grade (G)
II and G III tumors were differentiated from lipomas on the basis of the fractal
dimension and some other kinetic parameters, no differences were found between G
I tumors and lipomas. On the basis of the discriminant analysis, the
differentiation of soft-tissue tumors was best for the use of six parameters of
the FDG kinetics (SUV, VB, K1, k3, influx, and fractal dimension). Eighty-four
percent of G III tumors, 37.5% of G II tumors, 80% of G I tumors, 50% of lipomas,
and 14.3% of scars could be classified correctly, whereas inflammatory lesions
were misclassified. CONCLUSION: FDG PET should be used preferentially for
monitoring patients with G III sarcomas. Visual analysis provides a low
specificity. In contrast, the evaluation of the full FDG kinetics provides
superior information, particularly for the discrimination of G I and G III
tumors (positive predictive value, >80%).
