Metabolic Imaging of Pediatric Head and Neck Rhabdomyosarcoma: From Initial Staging to Treatment Response Assessment with F18-FDG PET/CT

Objective: To describe the staging and treatment-response characteristics of F18-FDG PET/CT in pediatric head and neck rhabdomyosarcoma (RMS) and their relationship with pretreatment stage and outcome.Materials and Methods: We retrospectively reviewed 21 pediatric patients (≤18 years) with head and neck RMS who underwent F18-FDG PET/CT. Pretreatment COG/IRS stage was confirmed in all patients (I = 9, II = 3, III = 8, IV = 1). Staging SUVmax was analyzed in 18 patients; 3 underwent postoperative-only PET/CT. Interval treatment-response PET/CT (n=15) was categorized as good/complete, minimal, or substantial residual response. Median follow-up was 23 months (range 9-92).Results: Median age was 5 years (range 2-17); 16 patients were male. Orbital tumors were the most common (38.1%), followed by parameningeal (33.3%) and non-parameningeal non-orbital sites (28.6%). Staging SUVmax increased with stage (3.5, 7.9, and 7.2 in stages I, II, and III; p=0.034; rho=0.55, p=0.019). Mortality was 62.5% in stage III versus 16.7% in stage I-II (p=0.062); the stage IV patient was alive. Among 15 patients with treatment-response imaging, 46.7% achieved good/complete response, 33.3% achieved minimal response, and 20% achieved substantial residual uptake; mortality did not differ by response tier (p=0.61).Conclusion: Pretreatment stage showed a trend toward association with outcome, with the highest mortality in stage III disease, and staging SUVmax correlated significantly with stage. Early metabolic response did not reliably predict outcome. F18-FDG PET/CT provides useful staging and treatment-response information but should be interpreted alongside clinical stage and close follow-up.