FDG PET/CT imaging of desmoplastic small round cell tumor: findings at staging, during treatment and at follow-up.

BACKGROUND: Desmoplastic small round cell tumor (DSRCT) is a very uncommon soft-tissue tumor of children and young adults. It has an aggressive course with generally poor survival. In general the assessment of tumor burden and response has relied upon CT or MRI. However these tumors are often metabolically active and can be evaluated using FDG PET/CT imaging.
OBJECTIVE: The purpose of this study was to determine the metabolic activity of desmoplastic small round cell tumors using FDG PET/CT imaging and the potential utility of FDG PET/CT in this disease.
MATERIALS AND METHODS: Eight patients (seven male, one female; ages 2-20 years, median 11 years) with confirmed DSRCT underwent 82 positron emission tomography/computed tomography (PET/CT) scans. PET/CT was used for initial staging (seven patients, eight scans), monitoring response to therapy (eight patients, 37 scans) and for surveillance of DSRCT recurrence (six patients, 37 scans).
RESULTS: Each scan performed at diagnosis showed abnormally elevated uptake in the primary tumor. Five patients had abdominal pelvic involvement, and two of those also had thoracic disease. Six patients whose scans showed no abnormal sites of uptake at the end of therapy have had progression-free survivals of 2-10 years. One patient whose scan continued to show uptake during treatment died of disease 1.3 years from diagnosis. Another patient with persistent uptake remained in treatment 3 years after initial diagnosis. One surveillance scan identified recurrent disease.
CONCLUSION: FDG PET/CT identified elevated metabolic activity in each patient studied. Despite our small sample size, FDG PET/CT scans appear useful for the management of patients with DSCRT. Patients whose studies become negative during or following treatment may have a prolonged remission.