Change in quantitative FDG-PET was significantly more accurate than change in size at predicting histopathologic response to neoadjuvant therapy in high grade soft tissue sarcomas

10017 Background: Change in size by RECIST (Response Evaluation Criteria in Solid Tumors) has been the standard to assess response to therapy in non-GIST soft tissue sarcomas (STS). Although recent studies have demonstrated that Positron Emission Tomography with F18-fluorodeoxyglucose (FDG-PET) may be used to assess response, there has not been a direct comparison between these modalities. The aim of this study was to prospectively evaluate whether a change in quantitative FDG-PET or a change in size [computed tomography(CT)] was more accurate at predicting histopathologic response to neoadjuvant therapy in patients with high grade STS using a combined FDG-PET/CT scan. Methods: From 1/05 - 12/06 58 patients with resectable biopsy proven high grade STS scheduled to undergo neoadjuvant chemotherapy were prospectively enrolled in this study. Patients underwent FDG-PET/CT prior to and after neoadjuvant treatment (prior to surgery). Tumor FDG-uptake was quantified by standardized uptake values (SUV). Changes i...