SURG-17: ENHANCED PERMEABILITY AND RETENTION OF INDOCYANINE GREEN: NOVEL DELIVERY TECHNIQUE FOR FLUORESCENT GUIDED TUMOR RESECTION

INTRODUCTION: Defining the precise margin for surgical resection of brain tumors remains a challenge, relying primarily on surgeon intuition and preoperative MR-imaging. Techniques in intraoperative fluorescent guided-surgery including 5-ALA and methylene blue have had limited success. Our group was interested in using a novel approach using indocyanine green (ICG), an FDA-approved fluorophore that has been in clinical use for 50 years. Recent work by our group has revealed that ICG can be used to target tumors through the enhanced permeability and retention (EPR) effect. We hypothesized that ICG could identify CNS tumors and margins due to the EPR effect. METHODS: Eleven patients with brain tumor pathology (meningioma, glioblastoma, metastasis) were consented and enrolled in this prospective IRB-approved study. Patients were administered 5 mg/kg ICG intravenously prior to elective craniotomy. Laser excitation at 805nm was used to excite the surgical wound in the operating room. VisionSenseTM camera was used to capture and display the NIR signal. 80 biopsy specimens were collected and analyzed by pathologist as gold standard. Test characteristics with 95% confidence intervals were calculated using STATA 10TM. RESULTS: All 11 patients underwent ICG infusion with no evidence of toxicity. During surgery, all tumors (n = 9) that enhanced with gadolinium on MRI demonstrated quantifiable NIR signal, whereas no tumor (n = 2) that did not enhance before surgery demonstrated NIR signal. Based on pathology, the sensitivity of white light alone for any tumor was 58.9% (45-71.9) versus 85.7% (73.8-93.6%) for NIR imaging (p < 0.01). In contrast, specificity of white light was 83.3% (62.6-95.3) versus 54.2% (32.8-74.4) for NIR imaging. CONCLUSION: Indocyanine Green can be used as an optical contrast agent for brain tumors by exploiting the enhanced permeability and retention effect. This technique may hold promise as a method for sensitive detection of the tumor:brain interface to improve resection of enhancing tumors of the central nervous system.