¹⁸F-FDG PET/CT in evaluating non-CNS pediatric malignancies

We reviewed our experience of ¹⁸F-FDG PET/CT in noncentral nervous system (CNS) pediatric malignancies and evaluated if PET/CT provided additional information to conventional imaging (CI) examinations to determine the efficacy of this new imaging modality in the clinical setting. Methods: One-hundred fiftyone consecutive FDG PET/CT examinations in 55 pediatric patients with non-CNS malignant tumors were reviewed. Among them, 108 PET/CT examinations were accompanied by CI, such as contrast CT or MRI, performed within a month of PET/CT in our hospital. Two radiologists reviewed the indication, purpose, and PET/CT findings and compared the findings with those of CI, if available, on the representative lesion in each of the 6 separate body regions. Positive findings included abnormal findings related to malignant lesions (suspected) as well as equivocal findings, in which the presence of malignancy could not be denied, but excluded findings considered to relate to past treatment. Accuracy of the findings was determined on the basis of the reference standard comprising histopathologic findings or informative follow-up of >1 y. An examination-based analysis was also performed in terms of additional information of PET/CT to CI. Results: There were 56 PET/CT-positive-CI-positive, 26 PET/CT-positive-CI-negative, and 54 PET/CT-negative-CI-positive lesions in 108 PET/CT examinations accompanied by CI, of which 54, 20, and 52 exhibited accurate PET/CT findings, respectively. Seventeen of the 20 PET/CT true-positive-CI falsenegative lesions represented small lymph nodes diagnosed as negative on CI. All 52 PET/CT true-negative-CI false-positive findings were observed in lesions in a posttreatment status including 30 mediastinal masses in lymphoma. Examination-based analysis revealed that additional information of PET/CT to CI was found in 37 (34%) of the 108 examinations: 23 (21%) as negative and 14 (13%) as positive PET/CT findings. Conclusion: PET/CT exhibited better diagnostic performance than CI and showed accurate findings in 90% (72/80) of lesions with discordant findings between them. Additional information of PET/ CT to CI was observed in more than one third of examinations compared. PET/CT was demonstrated to be an accurate imaging modality in evaluating pediatric patients with non-CNS malignancies.