Role of 18F-Fluorodeoxyglucose Positron Emission Tomography in Children With Germ Cell Tumor After Chemotherapy

Background/Aim: F-18-fluoro-2-deoxyglucose positron emission tomography/computed tomography (F-18-FDG PET/CT) is a diagnostic tool widely used in adult oncology and some pediatric oncological settings. There are no established recommendations for the use of this imaging modality in pediatric malignant germ cell tumors (mGCT), however. Our aim is to evaluate the role of F-18-FDG PET/CT in the restaging of mGCT after chemotherapy in children and adolescents. Methods: We retrospectively reviewed patients with mGCT treated in Associazione Italiana Ematologia Oncologia Pediatrica (AIEOP) centers who underwent F-18-FDG PET/CT between 2011 and 2021. Results: Seventeen patients (median age 13 y) were included in the study. In 14 patients, F-18-FDG PET/CT was performed at diagnosis; 12 showed pathologic uptake. The 2 F-18-FDG PET/CT negative cases were histologically defined as yolk sac tumor (YST) and mixed (chorioncarcinoma, YST). Nine of the 12 patients who had pathologic F-18-FDG PET/CT at diagnosis repeated the examination after neoadjuvant chemotherapy, before, second look surgery. In 5 cases, no pathologic uptake was evident. Histology showed necrosis alone in 4 cases and necrosis and mature teratoma in 1. In 3 of the 6 cases with pathologic uptake (2 of 6 patients did not perform the examination at diagnosis), histology showed persistence of malignant component, whereas in the remaining 3 cases, necrosis and mature teratoma were present. Conclusion: In our review of a series of children with mGCT, F-18-FDG PET/CT after neoadjuvant chemotherapy showed 1 of 5 false negatives and was unable to discriminate between residual malignant component and mature teratoma.