Abstract
PURPOSE: This study is aimed at evaluating the relationship between preoperative (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) findings and histopathological necrosis rates following chemotherapy in patients diagnosed with osteosarcoma (OST) and Ewing sarcoma (EWS). METHODS: Patients diagnosed with OST and EWS between 2017 and 2023 were retrospectively analyzed. Data recorded included preoperative (18)F-FDG PET/CT findings, demographic characteristics, histopathological diagnosis, maximum standardized uptake value at diagnosis (SUVmax1), maximum standardized uptake value after neoadjuvant chemotherapy (SUVmax2), the SUVmax change ratio (SUVmax2/SUVmax1 = SCR), and the percentage of tumor necrosis in resected specimens. RESULTS: A total of 49 patients (33 OST and 16 EWS) were included, consisting of 22 females (44.9%) and 27 males (55.1%) with a median age of 12 years (range: 4-20). Median SUVmax1, SUVmax2, and SCR values were 6.8 (0-22.5), 2.5 (0-9.42), and 0.38 (0-1.44), respectively. The median tumor necrosis percentage was 20% (range: 0-100). Stratification according to SUVmax2 (< 2.5 vs. ≥ 2.5) revealed no significant difference in necrosis percentage (p = 0.234). No significant correlation was observed between SCR and necrosis percentage (p = 0.102). However, a significant inverse correlation was found between SUVmax2 and necrosis percentage in the overall cohort (p = 0.040, r = -0.295), which was more pronounced in OST patients (p = 0.014, r = -0.426). CONCLUSION: (18)F-FDG PET/CT is a valuable imaging modality for predicting histopathological response in solid tumors. Consistent with adult studies, our findings demonstrate that post-NACT FDG uptake is inversely correlated with tumor necrosis percentage, particularly in pediatric OST patients. These results highlight the potential of (18)F-FDG PET/CT as a noninvasive prognostic tool to assist in early identification of poor responders.