Correlating Metabolic Activity on 18F-FDG PET/CT With Histopathologic Characteristics of Osseous and Soft-Tissue Sarcomas: A Retrospective Review of 136 Patients

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Abstract
OBJECTIVE. The objective of our study was to determine whether there is a statistically significant correlation between metabolic activity of osseous and soft-tissue sarcomas as measured by the maximum standardized uptake value (SUVmax) on 18F-FDG PET/CT and histopathologic characteristics such as mitotic counts, the presence of necrosis, and the presence of a myxoid component. MATERIALS AND METHODS. We retrospectively evaluated 238 consecutive patients with known soft-tissue or osseous sarcoma who underwent 18F-FDG PET/CT for initial staging or assessment for recurrence of disease. The SUVmax of each primary or of the most intense metastatic lesion was measured and was compared with the histologic data provided in the final pathology reports. RESULTS. Histopathologic data were available for 136 sarcomas. The median SUVmax values of sarcomas with mitotic counts of less than 2.00 (per 10 high-power fields [HPF]), 2.00–6.99, 7.00–16.24, and 16.25 or greater were 5.0, 6.6, 10.3, and 13.0, respectively (p = 0.0003). The median SUVmax for the sarcomas with necrosis (90 patients) was 8.6 and for those without necrosis (43 patients), 6.0 (p = 0.026). The median SUVmax for the sarcomas without a myxoid component (118 patients) was 7.7 and with a myxoid component (16 patients) was 6.2 (p = 0.28). CONCLUSION. There was a statistically significant correlation between the mitotic count and the SUVmax as well as between the presence of tumor necrosis and the SUVmax. Although a correlation between the presence of a myxoid component and SUVmax was shown, it was not found to be statistically significant. These findings improve on the current information in the literature regarding the use of PET/CT for guidance in sarcoma biopsy. Correlating the SUVmax with histologic markers that also feature prominently in major sarcoma grading systems may help improve the accuracy of grading and of prognostication by allowing the SUVmax to potentially serve as a surrogate marker in these grading systems, particularly in cases in which there is interobserver disagreement in the pathologic diagnosis or in cases in which the sarcoma cannot be properly classified on the basis of histopathologic evaluation alone.