Endoscopic Fluorescence-Guided Resection Increases Radicality in Glioblastoma Surgery

Abstract

BACKGROUND Several studies have proven the benefit of a greater extent of resection on progression-free survival and overall survival in glioblastoma (GBM). Possible reasons for incomplete tumor resection might be wrong interpretation of fading fluorescence or overseen fluorescent tumor tissue by a lacking line of sight between tumor tissue and the microscope. OBJECTIVE To evaluate if an endoscope being capable of inducing fluorescence might overcome some limitations of microscopic fluorescence-guided (FG) resection. METHODS 5-Aminolevulinic acid (20 mg/kg) was given 4 h before surgery. Microsurgical resection of all fluorescent tissue was performed. Then, the resection cavity was scanned with the endoscope. Fluorescent tissue, not being visualized by the microscope, was additionally removed and histopathologically examined separately. Neuronavigation was used for defining the sites of additional tumor resection. All patients underwent magnetic resonance imaging within 48 h after surgery. RESULTS Twenty patients with GBM were operated using microscopic and endoscopic FG resection. In all patients, additional fluorescent tissue was detected with the endoscope. This tissue was completely resected in 19 patients (95%). Eloquent localization precluded complete resection in the remaining patient. In 19 patients (95%), histopathological examination confirmed tumor in the additionally resected tissue. In 19 patients (95%), complete resection was confirmed. In all patients, endoscopic FG resection reached beyond the borders of contrast-enhancing tumor. CONCLUSION Endoscopic FG resection of GBM allows increasing the complete resection rate substantially and therefore is a useful adjunct to microscopic FG resection.

Endoscope-assisted fluorescence-guided resection allowing supratotal removal in glioblastoma surgery

“…After publication of a technical note in 2014, a first clinical series showed that residual fluorescent tumor tissue not visualized with the microscope could be detected with endoscopic assistance. 6,10 This finding is not surprising because inducing fluorescence is mainly related to adequate exposure to blue light. According to the inversesquare law ("illumination of a surface receiving its flux from a point source is inversely proportional to the square of the distance between the surface and the source"), the endoscope, as compared to the microscope, is capable of significantly reducing the distance between the light source and the tissue.…”

“…According to the inversesquare law ("illumination of a surface receiving its flux from a point source is inversely proportional to the square of the distance between the surface and the source"), the endoscope, as compared to the microscope, is capable of significantly reducing the distance between the light source and the tissue. 6 Besides the barriers of the depth of the surgical field, the presence of overhanging tissue or collapse of the resection cavity can lead to insufficient visualization of the tumor margins. 12 Furthermore, blind spots for microscopic FG resection can exist in the area of the craniotomy 10 as well as at the margin of the tumor due to collapse of the resection cavity.…”

“…12 Furthermore, blind spots for microscopic FG resection can exist in the area of the craniotomy 10 as well as at the margin of the tumor due to collapse of the resection cavity. 6 These blind spots can be visualized with the endoscope. Thus, endoscopic assistance appears to be a useful adjunct to increase the radicality of resection in GBM surgery.…”

“…Thus, endoscopic assistance appears to be a useful adjunct to increase the radicality of resection in GBM surgery. 6…”

“…A recently published study has shown that the assistance of an endoscope with a white and a blue light source, which is capable of inducing fluorescence, allows one to further increase the percentage of GTR by overcoming the limitations of the microscope. 6 However, the impact of combined microscopic and endoscopic FG resection on EOR has not been quantified. As previous studies have shown that malignant tumor cells spread beyond the areas of contrast enhancement on MRI, [7][8][9] the aim of our study was to determine if endoscope-assisted FG resection enables supratotal resection beyond the borders of contrast-enhancing GBM by comparing the volume of contrast-enhancing tumor on preoperative MRI with the volume of resected GBM tissue on postoperative MRI after such a resection.…”