Real-time in vivo kinetics of protoporphyrin IX after administration of 5-aminolevulinic acid in meningiomas and comparative analyses with glioblastomas.

Background: The usefulness of 5-aminolevulinic acid (5-ALA)–mediated fluorescence-guided surgery (FGS) in meningiomas is intensely discussed. However, data about kinetics of 5-ALA and protoporphyrin (Pp) IX in meningiomas are lacking. Methods: As the first study so far, we performed longitudinal intraoperative real-time ex situ measurements of fluorescence intensity and PpIX concentrations during FGS of ten benign and two atypical meningiomas. Kinetics were subsequently compared with data from 229 glioblastomas. Results: Spectroscopy revealed fluorescence (median 2945.65 a.u.) and PpIX accumulation (median 18.31 μg/ml) in all 43 analyzed samples. Fluorescence intensity (2961.50 a.u. vs 118.41 a.u.; p <.001) and PpIX concentrations (18.72 μg/ml vs.98 μg/ml; p <.001) were higher in samples with (N = 30) than without (N = 2) visible intraoperative tumor fluorescence. ROC curve analyses revealed a PpIX cut-off concentration of 3.85 μg/ml (AUC =.992, p =.005) and a quantitative fluorescence cut-off intensity of 286.73 a.u. (AUC =.983, p =.006) for intraoperative visible tumor fluorescence. Neither fluorescence intensity (p =.356) nor PpIX (p =.631) differed between atypical and benign meningiomas. Fluorescence and PpIX peaked 7–8 h following administration of 5-ALA. Meningiomas displayed a higher fluorescence intensity (p =.012) and PpIX concentration (p =.005) than glioblastomas 5–6 h after administration of 5-ALA. Although fluorescence was basically maintained, PpIX appeared to be cleared faster in meningiomas than in glioblastomas. Conclusions: Kinetics of PpIX and fluorescence intensity differ between meningiomas and glioblastomas in the early phase after 5-ALA administration. Modification of the timing of drug administration might impact visibility of intraoperative fluorescence and helpfulness of FGS and should be investigated in future analyses. [ABSTRACT FROM AUTHOR]