5-Aminolevulinic Acid Fluorescence-Guided Resection of 18F-FET-PET Positive Tumor Beyond Gadolinium Enhancing Tumor Improves Survival in Glioblastoma

Abstract BACKGROUND The value of early postoperative 18 F-FET-PET in patients with glioblastoma (GBM) is unclear. Five-aminolevulinic acid (5-ALA) is used for fluorescence-guided resections in these patients and previous data suggest that fluorescence and 18 F-FET-PET both demarcate larger tumor volumes than gadolinium enhanced magnet resonance imaging (MRI). OBJECTIVE To correlate fluorescence with enhancing volumes on postoperative MRI and 18 F-FET-PET tumor volumes, and determine the value of postoperative 18 F-FET-PET for predicting survival through observational study. METHODS GBM patients underwent fluorescence-guided resection after administration of 5-ALA followed by early postoperative MRI and 18 F-FET-PET for determination of residual tissue volumes. All patients were treated with standard temozolomide radiochemotherapy and monitored for progression-free and overall survival (PFS, OS). RESULTS A total of 31 patients were included. For functional reasons, residual 5-ALA derived fluorescent tissue was left unresected in 18 patients with a median 18 F-FET-PET volume of 17.82 cm 3 (interquartile range 6.50-29.19). In patients without residual fluorescence, median 18 F-FET-PET volume was 1.20 cm 3 (interquartile range 0.87-5.50) and complete resection of gadolinium enhancing tumor was observed in 100% of patients. A 18 F-FET-PET volume of above 4.3 cm 3 was associated with worse OS (logrank P -value ≤ .05), also in patients with no residual contrast enhancing tumor on MRI. More patients in whom fluorescencing tissue had been removed completely had postoperative 18 F-FET-PET tumor volumes below 4.3 cm 3 . CONCLUSION Postoperative 18 F-FET-PET volumes predict OS and PFS. Resection of 5-ALA derived fluorescence beyond gadolinium enhancing tumor tissue leads to lower postoperative 18 F-FET-PET tumor volumes and improved OS and PFS without additional deficits.