Confocal endomicroscopy accuracy in identifying central nervous system tumors tissue at the infiltration margins: results from a prospective clinical trial.

Background: We have previously shown the usefulness of a new confocal endomicroscopy system (CONVIVO^®) in providing a quick and reliable method for intraoperative diagnosis ex vivo in glioblastoma (GBM). In this study, we aimed to assess the intraoperative usefulness of CONVIVO^® in an in-vivo setting, focusing on its capability to explore the presence of residual tumor at the resection margins of Central Nervous System (CNS) tumors.

Methods: We consecutively enrolled patients submitted to fluorescein-guided CNS-tumor removal (May 2020 to December 2022). CONVIVO^® was used in vivo to obtain images from virtual biopsies at the central tumor core and at its margin of resection, evaluating its ability to offer a histological diagnosis at the center and a tumor tissue identification at the periphery, with respect to corresponding standard histological sections. CONVIVO^® images were analyzed before interpretation of permanent or frozen sections, with the pathologist being totally blinded to histological results.

Results: Seventy-five patients were studied. The most frequent diagnoses were GBM (50.6%) and metastasis (13.3%). At the tumor margins, on a total of 169 biopsies, we obtained an overall accuracy in tumor tissue identification of 82.2% (95% CI 75.0-89.5) in GBM/Grade 4 IDH-mutated astrocytomas, and 85.8% (95% CI 80.5-91.1) considering all tumors together. At the tumor center, a correct intraoperative diagnosis was obtained in 67.6% (95% CI 56.9-78.2) of all the cases, and in 80.9% (95% CI 69.1-92.8) of the GBM/Grade 4 IDH-mutated astrocytoma subgroup.

Conclusions: CONVIVO^® allowed to accurately assess the presence of pathological marginal tissue remnants during resection of aggressive CNS tumors. More studies are needed to evaluate if this could possibly improve the extent of resection.