Evaluation of 11C-Choline PET/CT for T Staging and Tumor Volume Delineation in Nasopharyngeal Cancer Patients in Comparison to 18F-FDG PET/CT

PurposeAccurate determination of the primary tumor extension of nasopharyngeal carcinoma (NPC) by F-18-FDG PET/CT is limited by the high physiological F-18-FDG uptake in the surrounding area, especially in the brain tissue. We aimed to assess whether C-11-choline PET/CT could improve the accuracy of T staging and tumor volume delineation for NPC patients.MethodsPatients with pathologically confirmed diagnosis of NPC were enrolled. The primary tumor extension of each patient was evaluated by C-11-choline PET/CT, F-18-FDG PET/CT, and contrast-enhanced MRI. The PET/CT-based tumor volume (V-PET) was measured by 3 threshold methods, including the threshold of SUV 2.5 (Th-2.5), 40% of maximal SUV (Th-40%), and the relative background-dependent threshold (Th-bgd). Tumor volume and Dice similarity coefficient were compared among V-PET with different segmentation methods and V-MR.ResultsThirty-three patients with treatment-naive NPC and 6 patients with suspicious recurrent disease were enrolled. The NPC lesions were avid for both C-11-choline and F-18-FDG. Visual analysis showed that C-11-choline PET/CT had better contrast and higher discernability than F-18-FDG PET/CT for intracranial, skull base, and orbital involvement. C-11-choline PET/CT also exhibited advantage over MRI for differentiation between local recurrence and radiation-induced alterations. For the tumor delineated, the V-MR was larger than V-PET in general, except for F-18-FDG PET/CT with Th-2.5 threshold. For all 3 threshold methods applied, C-11-choline PET/CT produced more consistent and comparable tumor volume to MRI than F-18-FDG PET/CT. C-11-choline PET/CT with Th-bgd threshold showed the closest tumor volume and highest similarity to MRI.Conclusions(11)C-choline PET/CT provides a higher accuracy than F-18-FDG PET/CT in mapping tumor extension in locally advanced NPC and may be a promising complement to MRI in delineating the primary tumor.