SURG-18. Results Utilizing the Tumor-Targeting Fluorescence Imaging Agent Tozuleristide and the Canvas Imaging System in an Exploratory Cohort of Adults Undergoing Resection of Vestibular Schwannoma

INTRODUCTION This investigator-initiated study evaluated tozuleristide (Blaze Bioscience, Inc.), a tumor-targeting near-infrared fluorescence-guided surgery (FGS) imaging agent in combination with the Canvas imaging system (Blaze Bioscience, Inc.), to aid in safe and effective resection of enhancing vestibular schwannoma tumors in the cerebellopontine angle. METHODS Adults undergoing initial resection of suspected vestibular schwannomas received 24 mg of tozuleristide 16-20 hours pre-operatively. The Canvas imaging system was used intraoperatively to visualize tumor fluorescence. The protocol specified that the surgeon biopsy regions of interest (ROI) identified under white light as definite tumor. Intraoperative fluorescence assessments of ROIs were obtained and compared to post-operative histopathology to correlate fluorescence with tumor. Subjects were not selected for capacity to safely achieve gross total resection (GTR). RESULTS Preliminary results from 3 subjects who underwent all study procedures indicate that 3/3 tumors were fluorescent. All biopsies were consistent with vestibular schwannoma by histopathology examination and were highly fluorescent. The facial nerve was identified and stimulated in all patients. In all patients, resection of tumor capsule was stopped when the facial nerve was no longer visualized due to being covered in fluorescent tissue. Two patients underwent GTR and near GTR (maximum tumor diameter 20.8mm and 25.5 mm) and one patient underwent subtotal resection (STR) (maximum tumor diameter 41.8mm). Near GTR patients had post-operative House Brackmann (HB) scores of 2 and 4 which improved to HB 1 and 2 within 6 months. The STR patient had HB score of 1. No residual fluorescence was seen in the patient with GTR. After administration of 24 mg tozuleristide pre-operatively, 100% of vestibular schwannomas exhibited fluorescence. The utility of tozuleristide fluorescence appears to be in distinguishing fluorescent tumor capsule and nerve. Further investigation in a larger study is warranted and may be generalizable to patients with other enhancing tumors of the skull base.