Comparison of Different Images in Gross Target Volume Delineating on VX2 Nasopharyngeal Transplantation Tumor Models

Background: To determine optimum conditions for diagnosis of nasopharyngeal carcinoma, we established VX2 rabbit model to delineate gross target volume (GTV) in different imaging methods. Methods: The orthotopic nasopharyngeal carcinoma (NPC) was established in sixteen New Zealand rabbits. After 7-days inoculation, the rabbits were examined by CT scanning and then sacrificed for pathological examination. To achieve best delineation, different GTVs of CT, MRI, 18F-FDG PET/CT, and 18F-FLT PET/CT images were correlated with pathological GTV (GTVp). Findings: We found a 45% and 60% of the maximum standardized uptake value (SUVmax) as the optimal SUV threshold for the target volume of NPC in 18F-FDG PET/CT and 18F-FLT PET/CT images, respectively (GTVFDG45% and GTVFLT60%). Moreover, the GTVMRI and GTVCT were significantly higher than the GTVp (P ≤ 0.05), while the GTVFDG45% and especially GTVFLT60% were similar to the GTVp (R = 0.892 and R = 0.902, respectively; P ≤ 0.001). Interpretation: Notably, the results suggested that 18F-FLT PET/CT could reflect the tumor boundaries more accurately than 18F-FDG PET/CT, MRI and CT, which makes 18F-FLT PET-CT more advantageous for the clinical delineation of the target volume in NPC. Funding Statement: This research received financial support from the Scientific Research Project Fund of the Affiliated Hospital of Southwest Medical University (2013-60). Declaration of Interests: The authors have no financial interests related to the material in the manuscript. The authors declare that there are no conflicts of interest. Ethics Approval Statement: This study was approved by an independent ethics committee/institutional review board at Department of Oncology, Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China. All animal-related procedures and protocol were approved under the guidelines of the National Institutes of Health (NIH) Animal Care (1995, USA) and the local Ethics Committee guidelines by Institutional Animal Care and Treatment Committee of Southwest Medical University (Luzhou, China).