gms | German Medical Science

Objective: Several Studies have proven the benefit of a wider extent of resection on progression-free survival and overall survival in glioblastoma (GBM) surgery. Thus, complete resection of the contrast-enhancing tumor tissue is a main surgical goal. Complete tumor removal can be increased from 36 to 65% by microscopic fluorescence-guided (FG) resection. One possible reason for incomplete tumor resection might be overseen fluorescent tumor tissue by a lacking line of sight between tumor tissue and the microscope. The aim of this study was to evaluate if an endoscope being capable of inducing fluorescence and visualizing hidden areas in the tumor cavity might overcome limitations of microscopic FG-resection.

Methods: A standard dose of 5-ALA of 20 mg/kg was given 4 hours before surgery. After completing microscopic FG resection, the resection cavity was scanned using the prototype of an endoscope with a blue light source to detect overseen fluorescent tissue. Residual fluorescent tissue was imbedded separately for histopathological examination. To identify residual contrast-enhancing tumor tissue patients received standard magnetic resonance imaging (MRI) within 48 hours after surgery. Neurological status was quantified by NIHSS pre- and postoperatively as well as the Karnofsky performance score (KPS).

Results: Twenty patients with GBM (12 male, 8 female) and a mean age of 73 years (46- 79) were operated, using microscopic as well as endoscopic FG-resection. Tumor location was temporal in 8, frontal in 7, parietal in 4 and occipital in 1 patient, respectively. The mean tumor volume was 28.4 ml. In all cases, fluorescent tissue that was not visualized by the microscope, was detected using the endoscope. In 19 patients (95%), histopathological examination confirmed residual tumor tissue in the separately preserved biopsies. In 18 patients (90%), complete resection was achieved. In all patients, endoscopic FG-resection was beyond the borders of MRI contrast-enhancement, documented by neuronavigation. The mean pre- and postoperative NIHSS was 1.1 (SD ± 0.91, SD ± 0.99). The mean postoperative KPS was 81,6 (SD ± 16.0).

Conclusion: Endoscopic FG-resection of GBM is a useful adjunct to microscopic FG resection to improve complete resection rate and to detect residual tumor tissue, not being visualized by the microscope. Furthermore, we have disproven that enhanced fluorescence within the tumor cavity is the result of auto-fluorescence of normal brain tissue.