gms | German Medical Science

Objective: Complete resection of the contrast-enhancing tumor tissue is a main surgical goal in patients with glioblastoma (GBM). Complete tumor removal can be increased from 36 to 65% by microscopic fluorescence-guided (FG) resection. Recently, a study was published showing that an endoscope being capable of inducing fluorescence, detects residual fluorescent tumor tissuenot being visualized by the microscope, and increases radicality. However, the influence on the extent of resection has not yet been quantified.

Methods: A standard dose of 5- ALA (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 residual fluorescent tissue, being not visualized by the microscope. The residual fluorescent tissue was completely resected and imbedded separately for histopathological examination. Non-enhanced and contrast-enhanced 3D T1w datasets acquired before and within 48 hours after tumor resection were analyzed using 3D Slicer. Bias field corrected data were used to segment brain parenchyma, tumor, and resection cavity in order to derive their volume as well as the differences in parenchymal volume pre- and post-surgery. Thus, the postoperatively quantified brain parenchyma volume is equivalent to the overall resected fluorescent tissue.

Results: 12 patients with GBM were included. The mean tumor volume was 52.22 cm³ (range 16.61–122.40 cm³). The mean volume of the resection cavity was 33.15 cm³ and significantly smaller than the tumor volume (p = 0.015). However, the mean volume of the overall resected fluorescent tissue was 114.09 cm³ and thus, significantly larger than the mean tumor volume (p< 0.001), yielding a mean volume of non-enhancing but fluorescent tissue of 61.87 cm³. The mean relative size of the overall resected volume compared to the tumor volume was 244.41 % (range 101–419 cm³). In all cases, histopathological examination confirmed residual tumor tissue in the separately preserved biopsies.

Conclusion: Endoscopic FG-resection of GBM is a useful adjunct to the microscope and allows supramarginal resection due to the detection of residual fluorescent tumor tissue, not being visualized by the microscope.