1-[11C]-acetate PET imaging in head and neck cancer--a comparison with 18F-FDG-PET: implications for staging and radiotherapy planning.

PURPOSE: The aim of this study was to evaluate the feasibility of using 1-[(11)C]-acetate positron emission tomography (ACE-PET) to detect and delineate the gross tumour volume of head and neck cancer before radiotherapy, and to compare the results with those obtained using (18)F-fluoro-2-deoxy-D: -glucose (FDG) PET.

METHODS: Ten patients with histologically verified squamous cell carcinoma were investigated by FDG-PET and dynamic ACE-PET prior to radiotherapy. The two scans were performed on the same day or on consecutive days, except in one patient in whom they were done 5 days apart. Diagnostic CT or MRI was performed in all patients. The image data sets were analysed both visually and semi-quantitatively. All primary tumours and metastases were delineated automatically by using the 50% threshold of maximum radioactivity corrected for background. The mean standardised uptake value (SUV) and the tumour volumes were evaluated and compared.

RESULTS: All ten primary tumours were detected by ACE-PET, while nine primaries were detected by FDG-PET and CT and/or MRI. The ACE SUV tended to be lower than the FDG SUV (5.3+/-2.7 vs 9.6+/-7.0, p=0.07). The tumour volumes delineated with ACE were on average 51% larger than the FDG volumes (p<0.05). ACE-PET identified 20/21 lymph node metastases, while only 13/21 lesions were detected by FDG-PET and 16/21 lesions by CT or MRI.

CONCLUSION: ACE-PET appears promising for the staging of head and neck cancer. The biological information provided by both FDG and ACE must be carefully validated before it can be used in clinical routine for radiation treatment planning. More studies are needed to evaluate the differences in volumes and to confirm the clinical potential of both FDG and ACE-PET, especially in radiotherapy.