Aim: To study the role of PET-CT in evaluating sarcomatous transformation in osteochondromas.
Materials and methods: This was a retrospective analysis of a prospective data base of 12 patients from 2005 to 2007 with a clinical diagnosis of an osteocartilaginous lesion who were referred for a FDG PET-CT study to evaluate for possible malignant transformation. Imaging was performed on a GE Discovery ST PET-CT system after intravenous injection of 370 MBq (10 mCi) of F-18 FDG.
Results: Seven patients with histopathological evidence of a sarcomatous transformation to grade II chondrosarcoma showed moderate to high FDG uptake (SUV 3.3-6.9), whereas 1 patient with a dedifferentiated chondrosarcoma showed a focus of very intense uptake (SUV 11.4). Four patients with histopathological and/or clinical or follow-up diagnosis of a benign osteocartilaginous lesion showed low grade FDG uptake (SUV 0.8-1.3). FDG uptake was also noted in an asymptomatic osteochondroma which on histopathology revealed a grade II chondrosarcoma.
Conclusions: Whole body FDG PET-CT is an important adjunct to conventional morphologic imaging in evaluating suspected malignant transformation in osteochondromas. Increased glucose metabolism can help diagnose sarcomatous transformation at the suspected sites as well as detect early malignant change at clinically unsuspected sites. Moreover, its ability to detect a focus of dedifferentiation can be useful for prognostication and to plan adjuvant treatment. A small cohort limits statistically sound conclusions to be drawn from this study, however further prospective trials based on these findings can help explore the potential application of FDG PET-CT in this clinical condition.