Optimal timing of first posttreatment FDG PET/CT in head and neck squamous cell carcinoma

BACKGROUND: The optimal timing for the initial posttreatment fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT scan after definitive treatment of head and neck squamous cell carcinoma (HNSCC) is unclear. METHODS: We conducted a retrospective review of 247 patients with definitively treated nonmetastatic HNSCC. First posttreatment PET/CT scans were grouped into: <7 weeks, 7 to 10 weeks, 11 to 14 weeks, and ≥15 weeks. Scans were categorized as positive or negative and accuracy of scans was calculated for each group using biopsy, subsequent imaging, or clinical follow-up for 1 year after treatment as a reference standard. RESULTS: Sixty-seven of the 247 patients (27.1%) had treatment failure. Scans performed at <7 weeks were less accurate than all other time intervals (p < .05). Scans performed at all other intervals were similar in accuracy. CONCLUSION: First posttreatment PET/CT can be obtained as early as 2 months after therapy. Scans performed earlier than 2 months have lower accuracy.