Professor of Surgery University of Pennsylvania Philadelphia, Pennsylvania
Near-Infrared Imaging of Canine Primary Lung Tumors Using a Cathepsin Activated Fluorophore. Holt D1, Huck J1, Bradley C1, Kennedy G2, Bensen E3, Singhal S2. 1University of Pennsylvania, School of Veterinary Medicine, Philadelphia, PA; 2University of Pennsylvania, School of Medicine, Philadelphia, PA; 3Vergent Biosciences, Minneapolis, MN.
Surgical tumor resection with complete margins is the most important predictor of patient survival for many solid tumors. Current methods of intraoperative tumor margin and regional lymph node assessment are lacking. We evaluated intraoperative, near-infrared (NIR) imaging using a cathepsin-activated NIR fluorophore for localization of canine primary lung tumors, margin assessment, and evaluation of regional lymph nodes in a pilot study. Four dogs with primary lung tumors underwent open thoracotomy and tumor excision following intravenous injection of VGT 309. Lungs were imaged using a NIR imaging device both in vivo and ex vivo. Tumor signal-to-background ratio (SBR) was measured in all cases. NIR imaging with VGT 309 identified all four lung tumors and their margins accurately (SBR = 2–3.3, median = 2.85, P < 0.001). One true positive and one false positive fluorescent bronchial lymph node were identified in separate cases. One fluorescent satellite pulmonary nodule showed marked histiocytic infiltration and no neoplasia on biopsy. Based on these preliminary results cathepsin-based NIR fluorophores show promise for identifying non-small cell lung tumors. However, cathepsins in macrophages may result in false positive fluorescence of regional lymph nodes and satellite pulmonary lesions.