292 Intraoperative Confocal Laser Endomicroscopy During 5-ALA Guided Glioma Surgery: Significant Considerations for Resection at the Tumor Margins

Abstract

INTRODUCTION: Fluorescence-guided surgery using 5-aminolevulinic acid (5-ALA) has proven effective in aiding the detection of glioma marginal zones and enhancing maximal safe resection. FDA-cleared confocal laser endomicroscopy is another imaging modality for intraoperative brain tissue discrimination on cellular level that could improve visualization at the glioma margin. METHODS: 5-ALA wide-field imaging and CLE were used in 9 patients with gliomas (6 enhancing, 3 non-enhancing). CLE imaging was enhanced by the use of a telesurgical pathology software platform to enable real-time conversation between neurosurgeons and pathologists located remotely. CLE was used for imaging tumor regions subjectively regarded as tumor margins under normal visualization with the operative microscope. After CLE imaging, 5-ALA wide-field imaging was performed in the same regions. A tissue was harvested at imaging locations, and interpretations of CLE and 5-ALA wide-field imaging were compared to permanent histological sections. RESULTS: Overall, 20 deep and superficial margin regions of interest (ROI) were imaged with CLE and 5-ALA imaging. Most of the ROIs interpreted by the neuropathologist as infiltrative glioma based on CLE imaging lacked 5-ALA-induced fluorescence. Permanent histological sections from the corresponding regions were concordant with the interpretation of CLE images in 15 of 20 (75%) ROIs and with the interpretation of 5-ALA imaging in 11 of 20 (55%) ROIs. Sensitivity/specificity of CLE and 5-ALA for interpretation of tumor margins were 79%/67%, and 50%/67%, respectively. Positive/negative predictive values for CLE and 5-ALA were 85%/57%, and 78%/37%, respectively. CONCLUSIONS: Conventional intraoperative understanding of tumor margins based on wide-field fluorescence could underestimate the invasiveness of gliomas. The ongoing study demonstrates that CLE shows higher accuracy in detecting regions with infiltrating tumor than intraoperative 5-ALA imaging.