Comparison of ¹⁸F-FDG-PET-CT and Bone Scintigraphy for Evaluation of Osseous Metastases in Newly Diagnosed and Recurrent Osteosarcoma

Background: Bone scintigraphy (BS) is used to detect osseous metastases in osteosarcoma. ¹⁸F-fluorodeoxyglucose-positron emission tomography–computed tomography (¹⁸F-FDG-PET-CT) is being increasingly used for staging. We compared the sensitivity, specificity, and diagnostic accuracy of ¹⁸F-FDG–PET-CT and BS for detecting osseous metastases in osteosarcoma. Methods: We retrospectively reviewed 39 patients with osteosarcoma who had paired PET–CT and BS at diagnosis and/or first recurrence from 2003 to 2012. Imaging studies were reviewed by two pediatric imaging specialists who were blinded to results of the opposing modality and reference standard. Reviewers categorized lesions as benign, malignant, or indeterminate. Reference standard for lesion histology was biopsy or clinical follow-up. Diagnostic performance of PET–CT, BS, and combined modalities were determined. Results: There were 40 examinations from 39 patients and 65 distant lesions were evaluated. Median age was 12 years (range 5–19 years). Four patients had 15 osseous metastases at diagnosis (two biopsied and 13 clinically), and two had five osseous metastases at recurrence (one biopsied and five clinically). For distant sites, sensitivity, specificity, and diagnostic accuracy were 79%, 89% and 86% for PET–CT, 32%, 96%, and 77% for BS, and 95%, 85%, and 88% for PET–CT/BS combined. Sensitivity of PET–CT was superior to BS (P = 0.035); combined imaging modalities were superior to BS (P < 0.001) but not better than PET–CT alone (P = 0.25). Specificity for BS approached significance compared to combined imaging (P = 0.063). Examination-based analysis yielded similar results between individual and combined imaging modalities. Conclusions: ¹⁸F-FDG–PET–CT demonstrated superior sensitivity over BS for detecting osseous metastases, supporting the use of ¹⁸F-FDG–PET–CT for staging of osteosarcoma.