Incorporation Of Fdg-Pet/Ct Into Radiation Therapy Planning To Improve Treatment Of Canine Nasal Tumors

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Loeber SJ, Custis JT, Randall EK, et al.

in Scientific Proceedings (Abstract). American College of Veterinary Radiology 2014.

Introduction/ Purpose: Nasal tumors in dogs are often malignant with a high rate of tumor recurrence and poor long-term survival. Metabolic imaging with 18- fluorodeoxyglucose-positron emission tomography-computed tomography (FOG- PET/CT) is a non-invasive means of quantifying tumor metabolic activity in the context of anatomic location. We hypothesize that FOG-PET/CT will allow us to better identify nasal tumor extent and highly metabolic, aggressive areas of the tumor compared to CT alone.

Methods: FOG-PET/CT scans were done in place of conventional radiotherapy planning CT on 7 dogs with probable nasal cancer that were admitted to the CSU Veterinary Teaching Hospital for radiotherapy. Tumor volumes and standardized uptake values (SUV , index of glucose metabolic activity) were compared from post-contrast CT , PET and fused PET/CT scans using 30-region-of-interest (ROI) analysis on the Philips Extended Brilliance Workstation (EBW).

Results: Nasal histopathologies included basal squamous cell carcinoma (n=3), adenocarcinoma (n=1) and chondrosarcoma (n=2). One additional dog had a nasal mass that was clinically presumed and treated as neoplastic, but histologically was Iymphocytic-plasmacytic rhinitis. The carcinomas were intensely hypermetabolic (11.8, 13.5, 20.9 and 25.91 max SUV). The chondrosarcomas were moderately hypermetabolic (4.22 and 5.28 max SUV) whereas the presumed, unconfirmed neoplasm was mildly hypermetabolic (2.3 max SUV). In 5/7 dogs, the contrast- enhanced CT volume mildly or substantially exceeded the PET volume, possibly because of enhancing peritumor reaction. In 2 of the dogs with carcinoma, the PET volume was 35-56% > CT volume indicating that some hypermetabolic infiltrate detected on PET was normal on CT. In all 7 dogs, the PET scan showed additional, different hypermetabolic regions of potential tumor not detected by CT.

Discussion/Conclusion: The combination of PET/CT has the best chance of identifying potential areas of tumor to target with radiotherapy, although peritumor reaction will also be included.