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

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.