Value of FDG positron emission tomography in conjunction with MR imaging for evaluating therapy response in patients with musculoskeletal sarcomas.

OBJECTIVE The purpose of our study was to investigate the potential of FDG positron emission tomography (PET) to distinguish viable tumor from changes caused by therapy in areas with equivocal MR imaging findings in patients with musculoskeletal sarcomas. MATERIALS AND METHODS We evaluated 12 patients (nine males, three females; age range, 9-56 years; mean age, 25 years) with a history of bone or soft-tissue sarcoma who had undergone various treatments (surgery, chemotherapy, radiation therapy, or a combination of treatments) and who presented with clinically suspected recurrent or residual tumor. All patients underwent gadopentetate dimeglumine-enhanced MR imaging and whole-body FDG PET. Imaging results were correlated with histologic findings or with clinical findings from long-term follow-up. RESULTS In nine patients, MR imaging findings were equivocal in differentiating between posttherapeutic changes and tumor recurrence. FDG PET images showed increased uptake, suggestive of recurrent tumor, in five patients. These findings were confirmed by biopsy. Four patients showed no increased uptake on FDG PET and were closely monitored clinically. No tumor recurrence was found in these patients. One patient showed MR imaging findings suggestive of recurrent tumor that was confirmed on FDG PET and at histology. Two patients underwent a limb salvage procedure before MR imaging, but MR images were deemed inadequate for interpretation because of extensive metallic artifacts. FDG PET was helpful in evaluating these patients for tumor recurrence. CONCLUSION FDG PET is a useful adjunct to MR imaging in distinguishing viable tumor from posttherapeutic changes in patients with bone and soft-tissue sarcomas.