Distribution of FDG PET and CT Imaging Results after Radiation

Objective: Both FDG PET and CT imaging can evaluate for persistent or recurrent malignancy after radiation treatment. Currently, there is a paucity of information about the discrepancy rates with these modalities. We want to determine the distribution of the results of posttreatment FDG PET/CT scans and their level of concordance.Method: We reviewed the records of 486 patients with head and neck squamous cell carcinoma who underwent a postradiation FDG PET/CT scan between 2000 to 2011. PET and CT positivity were defined as a standardized uptake value (SUV) of ≥ 3.0 and a lymph node size of ≥1 cm, respectively.Results: Sixty-four patients in whom 80 PET/CT scans were performed were eligible. A total of 62.5% (50) of the scans were both PET and CT negative. Scans that were PET positive and CT negative comprised 16.2% (13), while 11.3% (9) were PET negative and CT positive. The remaining 10.0% (8) had positive PET and CT scans. Among those with a positive CT scan (17), 47% (8) had a positive PET scan, yet am...