Top Line: Does FET-PET improve reirradiation outcomes for recurrent GBM?
The Study: Amino acid PET tracers provide a different way of looking at brain tumors than standard MRI. These tracers are more sensitive and have more contrast relative to background that FDG PET. Among these, 18F-fluoroethyltyrosine (FET) has been found to have higher specificity than contrast enhanced MRI in diagnosing recurrent GBM. GLIAA was a randomized trial that sought to determine if using FET-PET to treat recurrent GBM could increase PFS compared with standard MRI. It included 200 patients planned to be treated with reirradiation (39 Gy in 13 fractions) for recurrent GBM. They were randomized to have target volumes delineated using either FET-PET or MRI. Mean GTV volumes were similar with FET-PET and MRI (10.7 cc v 10 cc), however the GTV volumes did not completely overlap. The mean volume of overlap between FET-PET and MRI was 5.4 cc. In both arms, >90% of the GTV from the alternative modality was within the 30 Gy isodose line. The use of FET-PET did not significantly increase median PFS (4 v 4.9 months). There were also no significant differences in adverse events.
TBL: Using FET-PET did not significantly improve PFS compared to standard MRI in patients treated with reirradiation for GBM. | Grosu, Lancet Oncol 2025
The Study: Amino acid PET tracers provide a different way of looking at brain tumors than standard MRI. These tracers are more sensitive and have more contrast relative to background that FDG PET. Among these, 18F-fluoroethyltyrosine (FET) has been found to have higher specificity than contrast enhanced MRI in diagnosing recurrent GBM. GLIAA was a randomized trial that sought to determine if using FET-PET to treat recurrent GBM could increase PFS compared with standard MRI. It included 200 patients planned to be treated with reirradiation (39 Gy in 13 fractions) for recurrent GBM. They were randomized to have target volumes delineated using either FET-PET or MRI. Mean GTV volumes were similar with FET-PET and MRI (10.7 cc v 10 cc), however the GTV volumes did not completely overlap. The mean volume of overlap between FET-PET and MRI was 5.4 cc. In both arms, >90% of the GTV from the alternative modality was within the 30 Gy isodose line. The use of FET-PET did not significantly increase median PFS (4 v 4.9 months). There were also no significant differences in adverse events.
TBL: Using FET-PET did not significantly improve PFS compared to standard MRI in patients treated with reirradiation for GBM. | Grosu, Lancet Oncol 2025