ACTR-32. 5-ALA FLUORESCENCE IS A POWERFUL MARKER FOR DETECTION OF UNEXPECTED GLIOBLASTOMA TISSUE DURING SURGERY OF RADIOLOGICALLY SUSPECTED LOW-GRADE GLIOMAS

Abstract

BACKGROUND: Precise tissue sampling during resection of suspected low-grade gliomas (LGG) is the basis for an accurate histopathological diagnosis to enable adequate patient management. In the course of malignant transformation of initial LGG, small intratumoral areas of glioblastoma tissue can potentially arise that might be unrecognized during surgery and thus result in treatment failure. Recently, 5-aminolevulinic acid (5-ALA) induced fluorescence was identified as intraoperative marker for visualization of focal intratumoral WHO grade III areas. The aim of this study is thus to clarify if 5-ALA is also capable to identify areas of unexpected glioblastoma tissue during surgery of radiologically suspected LGG. METHODS: Our database at the Medical University of Vienna and University of California, San Francisco was screened for adult patients with 5-ALA fluorescence-guided resection of a suspected glioma with non-significant MRI contrast-enhancement (CE; no, patchy/faint or focal CE). In this study, only patients with newly diagnosed lesions were included. In contrast, recurrent gliomas and biopsy only cases were excluded. In all patients, histopathological diagnosis was established according to the WHO classification. RESULTS: Altogether, 7 patients (median age: 53 years, range: 30-66 years) with histological diagnosis of a glioblastoma were identified despite initial radiological suspicion of LGG. Of these, no CE was found on preoperative MRI in two cases (29%), patchy/faint CE in two cases (29%) and focal CE in three cases (42%). During surgery, intratumoral areas with focal 5-ALA induced fluorescence were observed in all 7 patients. In contrast, no visible fluorescence was found in the remaining intratumoral regions. CONCLUSIONS: Our study indicates that 5-ALA induced fluorescence is able to identify intratumoral areas containing even focal glioblastoma tissue in radiologically suspected LGG. Thus, the 5-ALA technique will in future markedly improve tissue sampling during resection of suspected LGG to allow a precise histopathological diagnosis and optimized postoperative patient management.