gms | German Medical Science

Objective: Tumor resection plays a role in the initial treatment but also in the setting of recurrent glioblastoma (rGBM). In order to achieve maximum resection, 5-aminolaevulinic acid (5’ALA) and intraoperative MRI (iMRI) can be used as surgical tools. 5’ALA is a very helpful fluorescent marker in first resection of GBMs, but recurrent GBM tumors sometimes show very little or only very weak fluorescence, making it difficult for the surgeon to identify tumor tissue, or to discriminate between recurrent tumor or radiation necrosis. In order to obtain best possible surgical results, we recently began to combine 5’ALA with iMRI.

Method: We have performed tumor resections for histologically proven rGBM in 7 patients, combining the use of 5-ALA (20 mk/kg bodyweight) with an iMRI device (0.15 T). We assessed intraoperative fluorescence findings, and compared fluorescence findings with intraoperatively obtained imaging. All patients had early postoperative MRI to verify final iMRI scans and received adjuvant treatment according to interdiscipliniary tumor board decision and were regularly followed.

Results: Median tumor volume was 8.2 cm³, median KPS was 90, and median patient age was 61 years. Intraoperatively, one tumor (14.3%) did not exhibit fluorescence. In contrast, all tumors were well visualized with iMRI and contrast media. In one patient, iMRI indicated residual tumor that was not identified with 5’ALA. Complete tumor resections could be achieved according to iMRI in all cases, which was later confirmed by early postoperative MRI. Median survival since repeat surgery was 6.6 months, while over all survival was 30.8 months according to Kaplan-Meier estimates

Conclusions: In setting of rGBM, not all tumors exhibit fluorescence after preoperative administration of 5’ALA. Repeat -surgeries should better be performed with the combined use of 5’ALA and iMRI in order to achieve best surgical results and to thus prolong patient’s’ survival.