Objectives: A previous study reported that a differential diagnosis between glioblastoma progression and radiation necrosis by 4-borono-2-[18F]-fluoro-phenylalanine ([18F]FBPA) PET can be made based on lesion-to-normal ratio of [18F]FBPA accumulation. Two-dimensional data acquisition mode PET alone system, with in-plane resolution of 7.9 mm and axial resolution of 13.9 mm, was used. In the current study, we aimed to confirm the differential diagnostic capability of [18F]FBPA PET/CT with higher PET spatial resolution by three-dimensional visual inspection and by measuring mean standardized uptake value (SUVmean), maximum SUV (SUVmax), metabolic tumor volume (MTV), and total lesion (TL) [18F]FBPA uptake.
Methods: Twelve patients of glioma (9), malignant meningioma (1), hemangiopericytoma (1), and metastatic brain tumor (1) were enrolled. All had preceding radiotherapy. High-resolution three-dimensional data acquisition mode PET/CT with in-plane resolution of 4.07 mm and axial resolution of 5.41 mm was employed for imaging. Images were three-dimensionally analyzed using the PMOD software. SUVmean and SUVmax of lesion and normal brain were measured. Lesion MTV and TL FBPA uptake were calculated. The diagnostic accuracy of [18F]FBPA PET/CT in detecting recurrence (n = 6) or necrosis (n = 6) was verified by clinical follow-up.
Results: All parameters showed significantly higher values for tumor recurrence than for necrosis. SUVmean in recurrence was 2.95 ± 0.84 vs 1.18 ± 0.24 in necrosis (P = 0.014); SUVmax in recurrence was 4.63 ± 1.23 vs 1.93 ± 0.44 in necrosis (P = 0.014); MTV in recurrence was 44.92 ± 28.93 mL vs 10.66 ± 8.46 mL in necrosis (P = 0.032); and mean TL FBPA uptake in recurrence was 121.01 ± 50.48 g vs 12.36 ± 9.70 g in necrosis (P = 0.0029).
Conclusion: In this preliminary feasibility study, we confirmed the possibility of differentiating tumor recurrence from radiation necrosis in patients with irradiated brain tumors by [18F]FBPA PET/CT using indices of SUVmean, SUVmax, MTV, and TL 18FBPA uptake.
Keywords: Brain tumor; FBPA; LAT1; PET; Radiation necrosis; Recurrence.