Although considerable progress has been made in the treatment of Ewing Sarcoma (ES), the prognosis of metastatic disease is unsatisfactory. 18 F-FDG-PET/CT (18 F-Fluorodeoxyglucose-Positron emission tomography/Computed tomography) is utilized for diagnosis, primary staging and therapy control. The prognostic significance of FDG-PET/CT is unknown and was examined in this study.
In this study, 21 patients with ES (female = 8, male = 13, median age 18 years) were analyzed. The PET/CT examination was utilized for primary staging and for therapy monitoring. 35 histological resected tissues as gold standard were compared with the PET/CT images. 33 resected tissues could be used for direct comparison of PET/CT with MRI (magnetic resonance imaging). The median follow-up was 30 months (range 9 - 109 months). The overall survival (OS) was estimated by Kaplan-Meyer. The PET/CT images were analyzed by the standardized uptake value (SUV).
The OS after 2 years was 66.7 % and 23.8 % after 5 years. Compared with 35 histological tissuses the FDG-PET/CT revealed a sensitivity of 96% and a specificity of 90%; the corresponding positive (PPV) and negative predictive values (NPV) were 96 % and 90 %. A direct comparison of PET/CT and MRI revealed a sensitivity of 96 % (PET/CT), 92 % (MRI), a specificity of 100 % (PET/CT), 62.5 % (MRI), PPV of 100 % vs, 88 % and NPV of 89 % vs. 71 %. Patients with negative FDG-PET/CT findings had a very good overall survival of 90 %, while the prognosis of patients with positive FDG-PET/CT images remains poor (19 %). Furthermore, the evaluation of tumoral FDG uptake before and after therapy demonsrated that the SUV after chemotherapy could also be predictive in terms of survival (p = 0.0007).
FDG-PET/CT has become a high diagnostic value in the evaluation of initial tumor diagnosis, restaging and assessment of therapy response in patients with ES. Patients with ES and negative follow-up PET/CT imaging have an excellent OS. Despite intensive multimodal therapy concepts, the OS of patients with positive follow-up imaging is poor. Responders showed a decrease of the SUV, non-responders an increase. Both modalities, MRI and PET/CT detected different qualities of the tumor manifestations.||dc.description.abstract