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PRELIMINARY EVALUATION OF SERIAL 18FDG-PET/CT TO ASSESS RESPONSE TO TOCERANIB PHOSPHATE THERAPY IN CANINE CANCER

Authors


  • Presented in oral abstract format at the annual American College of Veterinary Radiology meeting, August 15–19, 2010; Asheville, NC.

Address correspondence and reprint requests to Amy K. LeBlanc, Associate Professor and Director of Translational Research Veterinary Medical Center, University of Tennessee 2407 River Drive Knoxville, TN 37996 (865) 755-8213 and Director of Translational Research, Imaging and Translational Research Program; Graduate School of Medicine, University of Tennessee Medical Center 1924 Alcoa Highway Knoxville, TN 37920 (865) 305-6188. Email: aleblanc@utk.edu.

Abstract

PalladiaTM (toceranib phosphate—Pfizer Animal Health) is a novel orally administered receptor tyrosine kinase inhibitor (TKI) approved for treatment of canine mast cell tumors. Receptor tyrosine kinase dysregulation leads to tumor growth, progression, and metastasis. Toceranib's targets include vascular endothelial growth factor receptor (VEGFR-2/Flk-1/KDR), platelet-derived growth factor receptor, and kit. Positron Emission Tomography/Computed Tomography (PET/CT) is used commonly to diagnose, prognosticate, and monitor response to antineoplastic therapy in human patients. In this study, serial PET/CT imaging with 18F-fluorodeoxyglucose (18FDG) was used to assess response to toceranib therapy in dogs with measurable solid malignancies. Six tumor-bearing dogs underwent tumor assessment using both standard RECIST criteria and PET/CT prior to and at a median of 5 weeks postinitiation of toceranib treatment. Toceranib was prescribed initially at a target dose 3.25 mg/kg PO q48 h, with subsequent modifications based on observed toxicity. Treatment was continued in patients achieving stable disease with acceptable drug tolerance. One dog was maintained on drug despite dose modification due to toxicity; measurable clinical and image-based responses were seen after 10 weeks of therapy. All others had stable or progressive disease based on clinical restaging and PET/CT at first recheck. . Due to discordance with anatomic and metabolic imaging, further studies are needed to investigate the role of molecular imaging in assessment of drug response and identify other potential molecular targets of toceranib.

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