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

Abstract

Purpose Accurate determination of the primary tumor extension of nasopharyngeal carcinoma (NPC) by 18F-FDG PET/CT is limited by the high physiological 18F-FDG uptake in the surrounding area, especially in the brain tissue. We aimed to assess whether 11C-choline PET/CT could improve the accuracy of T staging and tumor volume delineation for NPC patients. Methods Patients with pathologically confirmed diagnosis of NPC were enrolled. The primary tumor extension of each patient was evaluated by 11C-choline PET/CT, 18F-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 (Th2.5), 40% of maximal SUV (Th40%), and the relative background-dependent threshold (Thbgd). Tumor volume and Dice similarity coefficient were compared among V PET with different segmentation methods and V MR. Results Thirty-three patients with treatment-naive NPC and 6 patients with suspicious recurrent disease were enrolled. The NPC lesions were avid for both 11C-choline and 18F-FDG. Visual analysis showed that 11C-choline PET/CT had better contrast and higher discernability than 18F-FDG PET/CT for intracranial, skull base, and orbital involvement. 11C-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 18F-FDG PET/CT with Th2.5 threshold. For all 3 threshold methods applied, 11C-choline PET/CT produced more consistent and comparable tumor volume to MRI than 18F-FDG PET/CT. 11C-choline PET/CT with Thbgd threshold showed the closest tumor volume and highest similarity to MRI. Conclusions 11C-choline PET/CT provides a higher accuracy than 18F-FDG PET/CT in mapping tumor extension in locally advanced NPC and may be a promising complement to MRI in delineating the primary tumor.