Grading of tumors and tumorlike lesions of bone: Evaluation by FDG PET

Clinical diagnosis of skeletal tumors can be difficult, because such lesion s compose a large, heterogeneous group of entities with different biologic behaviors. The aim of this prospective study was to assess the value of PET in grading tumors and tumorlike lesions of bone. Methods: Two hundred two patients with suspected primary bone tumors were investigated using FDG PET . Uptake of FDG was evaluated semiquantitatively by determining the tumor-t o-background ratio (T/B). All patients underwent biopsy, resulting in the h istologic detection of 70 high-grade sarcomas, 21 low-grade sarcomas, 40 be nign tumors, 47 tumorlike lesions, 6 osseous lymphomas, 6 plasmacytomas, an d 12 metastases of an unknown primary tumor. Results: All lesions, with the exception of 3 benign tumors, were detected by increased FDG uptake. Altho ugh sarcomas showed significantly higher T/Bs than did latent or active ben ign lesions (P < 0.001), aggressive benign lesions could not be distinguish ed from sarcomas. Using a T/B cutoff level for malignancy of 3.0, the sensi tivity of FDG PET was 93.0%, the specificity was 66.7%, and the accuracy wa s 81.7%. Conclusion: FDG PET provides a promising tool for estimating the b iologic activity of skeletal lesions, implicating consequences for the choi ce of surgical strategy.