Fluorescence Guidance in Glioma Surgery: A Narrative Review of Current Evidence and the Drive Towards Objective Margin Differentiation.

Fluorescence-guided surgery (FGS) was pioneered for glioma and is now established as the standard of care. Gliomas are infiltrative tumours with diffuse margins. FGS provides improved intra-operative identification of tumour margins based on tumour-specific emission visible to the operating surgeon, resulting in increased rates of gross total resection. Multiple fluorescence agents may be used including 5-ALA, fluorescein sodium, and indocyanine green (ICG). This review details the indication, required equipment, mechanism of action, evidence base, limitations, and regulatory issues for each fluorophore as utilised in current clinical practice. FGS for glioma is limited by a reliance on subjective interpretation of visible fluorescence, which is often not present in low-grade glioma (LGG) or at the infiltrative tumour margin. Consequently, there has been a drive to develop enhanced, objective FGS techniques utilising both quantitative fluorescence (QF) imaging systems and novel fluorophores. This review provides an overview of emerging QF imaging systems for FGS. The pipeline for novel fluorophore development is also summarised.