gms | German Medical Science

Objective: While the contribution of 5-aminolaevulinic acid (5-ALA) and intraoperative MRI (iMRI) on their own to optimize the extent of resection in glioblastoma (GBM) surgery is obvious, a possible benefit of simultaneous use of both methods in resection guidance remains elusive. In this study we compared combined 5-ALA/1.5T iMRI guidance vs. iMRI-guidance alone.

Method: From our prospective iMRI data-base 10 primary GBM patients with combined 5-ALA/iMRI-guided resections were identified between 01/2011 and 05/2012. Ten cases of sole iMRI-guided resections were matched according to tumor location and size (in cm³). Complete resection of contrast enhancement (CE) was aspired in all 20 cases; the surgeon’s evaluation of resection progress was obtained before the first iMRI scan.

Results: Average tumor volume was 24,17 cm³ ± 19,65 cm³ in the 5-ALA/iMRI and 22,73 cm³ ± 11,50 cm³ in the iMRI group. After a first iMRI scan, fewer continued resections and smaller intraoperative tumor remnants were seen in combined 5-ALA/iMRI resections (5 vs. 7 continued resections, 0,75 cm³ ± 1,36 cm³ vs. 1,07 cm³ ± 1,08 cm³ residual tumor for 5-ALA/iMRI vs. iMRI alone, respectively). Complete resection of CE was achieved in 18/20 cases, with small tumor remnants diagnosed in one patient of each group on postoperative MRI (0,5 cm³ for 5-ALA/iMRI vs. 0,14 cm³ for iMRI alone). Evaluating the resection progress, surgeons did not expect continued post-iMRI resections in 7/10 cases in both groups. This estimation is discrepant to the high frequency of continued resections observed (50% for 5-ALA/iMRI and 70% for iMRI alone). One patient in each group showed new permanent neurologic deficits. Tendency for transient deficits was higher in the 5-ALA/iMRI group (3 vs. 1 transient deficit, respectively).

Conclusions: Combined 5-ALA/iMRI guidance leads to fewer post iMRI resections and reduced tumor volumes on intraoperative scans, but additional fluorescence feedback did not influence the surgeons’ intraoperative impression: uncertainty about tumor remnants persisted. After resection of 5-ALA hotspots, superior resolution in iMRI enabled to unveil residual contrast enhancing tumor also within areas of sluggish fluorescence. 5-ALA/iMRI combination did not result in an increased rate of complete tumor resections compared to the use of iMRI alone. Future prospective studies have to confirm these preliminary results and identify useful indications for a combined use of both imaging modalities on a larger scale.