¹⁸F-FDG-PET/CT in initial staging and assessment of early response to chemotherapy of pediatric rhabdomyosarcomas.

Purpose: The objective of this retrospective study was to compare positron emission tomography/computed tomography using fluorine-18-fluorodeoxyglucose (18F-FDG-PET/CT) and conventional imaging modalities (CIM) in initial staging and early assessment of response to chemotherapy in children and young adults treated for rhabdomyosarcoma (RMS).

Patients And Methods: At initial staging, 23 patients (9 months to 21 years) with histologically proven RMS underwent 18F-FDG-PET/CT in addition to CIM (MRI of the primary site, whole-body CT, and bone scintigraphy). After three courses of chemotherapy, 13 patients underwent 18F-FDG-PET/CT in addition to CIM. RECIST criteria and visual analysis of 18F-FDG uptake were used for assessment of response. The standard of reference was determined by an interdisciplinary tumor board on the basis of imaging material, histopathology, and follow-up data (median = 5 years).

Results: 18F-FDG-PET/CT sensitivity was superior to that of CIM for determination of lymph node involvement (100 vs. 75%) and detection of metastases (100 vs. 66%). 18F-FDG-PET/CT results changed therapeutic management in 13% of cases. After three courses of chemotherapy 18F-FDG-PET/CT was able to detect 92% of objective responses compared with 84% by CIM. The rate of complete response was 69% with 18F-FDG-PET/CT compared with 8% with CIM.

Conclusion: This study confirms that 18F-FDG-PET/CT reveals important additional information at initial staging of pediatric RMS, which suggests a superior prognostic value of 18F-FDG-PET/CT in early response to chemotherapy assessment.