Diagnostic value of PET/CT for the staging and restaging of pediatric tumors

Objective The objective of this retrospective study was to compare the diagnostic value of 2-[F-18]fluoro-2-deoxy-D-glucose positron emission tomography (F-18-FDG PET)/CT versus F-18-FDG PET and CT alone for staging and restaging of pediatric solid tumors. Methods Forty-three children and adolescents (19 females and 24 males; mean age, 15.2 years; age range, 6-20 years) with osteosarcoma (n=1), squamous cell carcinoma (n=1), synovial sarcoma (n=2), germ cell tumor (n=2), neuroblastoma (n=2), desmoid tumor (n=2), melanoma (n=3), rhabdomyosarcoma (n=5), Hodgkin's lymphoma (n=7), non-Hodgkinlymphoma (n=9), and Ewing's sarcoma (n=9) who had undergone F-18-FDG PET/CT imaging for primary staging or follow-up of metastases were included in this study. The presence, location, and size of primary tumors was determined separately for PET/CT, PET, and CT by two experienced reviewers. The diagnosis of the primary tumor was confirmed by histopathology. The presence or absence of metastases was confirmed by histopathology (n=62) or clinical and imaging follow-up (n= 238). Results The sensitivities for the detection of solid primary tumors using integrated F-18-FDG PET/CT (95%), F-18-FDG PET alone (73%), and CT alone (93%) were not significantly different (p>0.05). Seventeen patients showed a total of 153 distant metastases. Integrated PET/CT had a significantly higher sensitivity for the detection of these metastases (91%) than PET alone (37%; p<0.05), but not CT alone (83%; p>0.05). When lesions with a diameter of less than 0.5 cm were excluded, PET/CT (89%) showed a significantly higher specificity compared to PET (45%; p<0.05) and CT (55%; p<0.05). In a sub-analysis of pulmonary metastases, the values for sensitivity and specificity were 90%, 14%, 82% and 63%, 78%, 65%, respectively, for integrated PET/CT, stand-alone PET, and stand-alone CT. For the detection of regional lymph node metastases, F-18-FDG PET/CT, F-18-FDG PET alone, and CT alone were diagnostically correct in 83%, 61%, and 42%. A sub-analysis focusing on the ability of PET/CT, PET, and CT to detect osseous metastases showed no statistically significant difference between the three imaging modalities (p>0.05). Conclusion Our study showed a significantly increased sensitivity of PET/CT over that of PET for the detection of distant metastases but not over that of CT alone. However, the specificity of PET/CT for the characterization of pulmonary metastases with a diameter>0.5 cm and lymph node metastases with a diameter of <1 cm was significantly increased over that of CT alone.