gms | German Medical Science

Objective: Fluorescein sodium has generated renewed interest for off-label use in fluorescence-guided resections of malignant gliomas due to potential advantages such as bright fluorescence and the possibility of intravenous application. We sought to simultaneously visualize 5-aminolevulinic acid (5-ALA) derived protoporphyrin IX (PPIX) and fluorescein fluorescence in order to detect synergies between both methods.

Method: A specialized microscope system (Leica, Heerbrugg, Switzerland) was used to visualize of both fluorescein and PPIX fluorescence in each patient. 5-ALA was administered 4 hours prior to surgery (20 mg/kg). Fluorescein (4 mg/kg, 10% solution) was applied at two different time points, either before dura opening (n=2; 1 Glioblastoma, 1 recurrent low-grade glioma) or after resection of the tumor bulk (n=2, both Glioblastoma).

Results: Neither time point of application resulted in significant fluorescein fluorescence preferentially marking tumor tissue in the low-grade or the high-grade glioma patients. Fluorescein fluorescence was observed in the dura, cortex and vessels, and was found in oozing blood which contaminated the surrounding structures. Fluorescein extravasation was also noted in areas of surgical tissue injury. Specific PPIX fluorescence was observed in all three Glioblastoma (GBM) patients, but not in the low-grade glioma patient. Surprisingly, fluorescein did not appear to accumulate in viable, marginal tumor tissue with clear PPIX fluorescence. No surgical decisions were made based on fluorescein fluorescence. Due to the lack of exploitable fluorescein fluorescence this pilot study was prematurely closed.

Conclusions: Our observations do not support a useful role for fluorescein sodium in fluorescence-guided resections of gliomas.