EP03.02 IMAGING-BASED PREDICTION OF 5-ALA FLUORESCENCE IN GLIOMAS USING PREOPERATIVE 7T MRSI COMPARED TO T1W MRI AND PET

Abstract BACKGROUND Maximizing the extent of safe tumor resection is a critical factor influencing survival outcomes in glioma patients. The use of 5-aminolevulinic acid (5-ALA) fluorescence has proven effective in enhancing resection, particularly in high-grade gliomas (HGG), where it is routinely applied. However, its utility in low-grade gliomas (LGG), especially those without significant contrast enhancement (CE), remains unclear. Clinically, T1-weighted contrast-enhanced MRI and PET imaging have shown strong associations with intraoperative 5-ALA fluorescence. This study investigated whether 7T Magnetic Resonance Spectroscopic Imaging (MRSI) could serve as a reliable preoperative tool to predict 5-ALA fluorescence, comparing its performance to that of established imaging modalities. MATERIAL AND METHODS We retrospectively evaluated 42 patients with histologically confirmed diffusely infiltrating adult-type gliomas who underwent preoperative 7T MRSI and 5-ALA fluorescence-guided surgery. Group comparisons were conducted using the Mann-Whitney U test and Chi-square test. Predictive performance was assessed using receiver operating characteristic (ROC) curve analysis and multivariate logistic models. RESULTS Significantly higher median metabolite ratios were observed in 5-ALA-positive tumors compared to 5-ALA-negative ones: Gln/tCr (p<0.001), Glx/tCr (p<0.001), Gly/tCr (p<0.001), and GSH/tCr (p<0.001) were observed in 5-ALA-positive tumors compared to 5-ALA-negative ones. The ratio of mIns/tNAA was significantly lower in the 5-ALA positive compared to the 5-ALA negative group. ROC analysis revealed strong predictive accuracy for 5-ALA fluorescence using: mIns/tNAA (81%) Gln/tCr (88%), Glx/tCr (87%), Gly/tCr (86%), and GSH/tCr (83%), with the combined accuracy of 94%. In comparison, the presence of CE on MRI predicted fluorescence was predicted in 68% of cases, while PET imaging predicted it in 86%. CONCLUSION Preoperative quantification of mIns/tNAA, Gln/tCr, Glx/tCr, Gly/tCr, and GSH/tCr ratios via 7T MRSI may effectively predict intraoperative 5-ALA fluorescence. These findings support the use of ultra-high-field MRSI as a valuable tool for surgical planning and patient selection for 5-ALA administration, with the potential to improve resection outcomes in glioma treatment.