Objective: The sensitivity of 5-aminolevolinic acid (5-ALA) in detecting intraoperative glioblastoma (GBM) tissue compared to postoperative (18)F-fluoroethyl-L-tyrosine and T1 contrast uptake of tumor cells in positron emission tomography (PET) and magnetic resonance imaging (MRI) scans was investigated in a retrospective image correlative study.
Methods: Ten patients with histological verified GBM in eloquent brain regions underwent 11 surgeries with neuronavigation and 5-ALA assisted tumor resection. Residual 5-ALA fluorescence was labeled intraoperatively on the navigation MRI scans and images were fused with postoperative (18)F-FET PET and T1 contrast MRI.
Results: Intraoperatively, at the end of save resection, in all patients 2-5 faint 5-ALA positive resection planes were detected (mean 3·6), compared to 0-4 (18)F-FET positive resection planes (mean 1·4) and 0-2 positive T1 contrast MRI resection planes in postoperative scans. The difference between the number of 5-ALA and (18)F-FET positive resection planes was statistically significant (P = 0·0002). The histological investigation of 5-ALA positive resection margins demonstrated infiltrative tumor in every case. Residual 5-ALA fluorescence on resection margins and postoperative (18)F-FET uptake areas or residual contrast T1 areas were colocalized in all cases, documented by pre-/postoperative image fusion.
Conclusion: Residual faint 5ALA uptake is documented in large areas at the end of GBM resection and corresponds to tumor infiltration. These 5-ALA positive resection plans exceeded the (18)F-FET uptake areas in postoperative PET scans. Thus, intraoperative 5-ALA residual fluorescence seems to be a more sensitive marker than (18)F-FET PET for residual tumor in malignant gliomas.