Improving the Extent of Malignant Glioma Resection by Dual Intraoperative Visualization Approach

Abstract

Despite continuing debates around cytoreductive surgery in malignant gliomas, there is broad consensus that increased extent of tumor reduction improves overall survival. However, maximization of the extent of tumor resection is hampered by difficulty in intraoperative discrimination between normal and pathological tissue. In this context, two established methods for tumor visualization, fluorescence guided surgery with 5-ALA and intraoperative MRI (iMRI) with integrated functional neuronavigation were investigated as a dual intraoperative visualization (DIV) approach. Thirty seven patients presumably suffering from malignant gliomas (WHO grade III or IV) according to radiological appearance were included. Twenty-one experimental sequences showing complete resection according to the 5-ALA technique were confirmed by iMRI. Fourteen sequences showing complete resection according to the 5-ALA technique could not be confirmed by iMRI, which detected residual tumor. Further analysis revealed that these sequences could be classified as functional grade II tumors (adjacent to eloquent brain areas). The combination of fluorescence guided resection and intraoperative evaluation by high field MRI significantly increased the extent of tumor resection in this subgroup of malignant gliomas located adjacent to eloquent areas from 61.7% to 100%; 5-ALA alone proved to be insufficient in attaining gross total resection without the danger of incurring postoperative neurological deterioration. Furthermore, in the case of functional grade III gliomas, iMRI in combination with functional neuronavigation was significantly superior to the 5-ALA resection technique. The extent of resection could be increased from 57.1% to 71.2% without incurring postoperative neurological deficits.

Accuracy of High-Field Intraoperative MRI in the Detectability of Residual Tumor in Glioma Grade IV Resections

“…Gessler described that ioMRI was the only indicator for residual tumor in only 26.3 % of cases and fluorescence guidance in 21.1 % of cases. Gessler et al agree with Eyüpoglu that 5-ALA may by misleading if tumorous tissue is hidden by healthy tissue, spatula or blood [25], and complementary use of ioMRI may help to avoid these pitfalls [5]. In this study the sensitivity was 75 % and the specificity was 100 % for ioMRI, while the sensitivity was 70 % and the specificity was 100 % for fluorescence guidance.…”

“…They stated that the accuracy of ioMRI might be underestimated due to this limitation, and that ioMRI shows an underdetection of solid tumor masses. This goes along with the findings of Eyüpoglu and Gessler [5,17], who both revealed inconsistent findings between ioMRI and fluorescence guidance. Gessler described that ioMRI was the only indicator for residual tumor in only 26.3 % of cases and fluorescence guidance in 21.1 % of cases.…”

“…Eyüpoglu et al used high-field (1.5 T) ioMRI and ALA-guided resection and could show that the extent of resection increases from 84 % to 99 % with the additional usage of ioMRI. The combination with 5-ALA-guided resection was also advantageous in the vicinity of eloquent brain regions, facilitating more radical resection compared to 5-ALA alone [5]. Showing 97 % resectability of contrast-enhancing tissue after intraoperative MRI [24], high-field ioMRI in our study showed a sensitivity of 95 % but a rather low specificity of 69.5 %, which was related to scars, bleeding, artifacts and a personal factor of a higher affinity to decide for a second resection if contrast enhancement was seen, to avoid misinterpretations leading to remaining contrast-enhancing tumorous tissue.…”

“…In summary, complementary use of fluorescence guidance, intraoperative ultrasound and/or ioMRI may optimize resection rates and can be regarded as a contemporary operative setting in glioma surgery, although it is not proven so far that ioMRI is crucial to increase resection rates of tumorous tissue [5,17]. So far, the gold standard to define the extent of resection and to detect tumor borders in MRI is GD-DPTA enhancement [26].…”

Tumor detection with 5-aminolevulinic acid fluorescence and Gd-DTPA–enhanced intraoperative MRI at the border of contrast-enhancing lesions: a prospective study based on histopathological assessment

“…However, due to these studies' small sample sizes no final conclusion can be drawn. 4,28 In our opinion the combined use of both techniques might increase safety of 5-ALA-guided resection close to eloquent areas and would overcome the issue of missed fluorescence in concealed regions of the resection cavity. Furthermore, the lower specificity of 5-ALA in comparison with iMRI would be balanced.…”