Metabolic characteristics of [18F]fluoroboronotyrosine (FBY) PET in malignant brain tumors

[18F]fluoroboronotyrosine (FBY) is a large neutral amino acid transporter 1 (LAT-1) dependent boron-derived tyrosine which has diagnostic and therapeutic potentiality. This study aimed to investigate the imaging characteristics of FBY positron emission tomography (PET) in malignant brain tumors.A total of 35 patients with 36 lesions were prospectively enrolled for FBY positron emission tomography (PET) and magnetic resonance imaging (MRI). Three-dimensional region of interest was semiautomatically defined on MRI and coregistered to FBY PET images. Five quantitative parameters, namely, standardized uptake value (SUV) maximum (SUVmax), SUVmean, metabolic tumor volume (MTV), total lesion activity (TLA) and tumor-to-normal ratio (T/N ratio), were calculated. The mean and standard deviation values of the parameters in different circumstances were calculated, and the Wilcoxon rank-sum test was applied to reveal the differences of FBY parameters.The maximum and mean standardized uptake value (SUV) of the normal brain were 0.119 ± 0.030 and 0.038 ± 0.017 in the study cohort. Majority of the neoplastic lesions displayed elevated FBY uptake, with SUVmax of 0.26 ± 0.14, 3.00 ± 0.61, 2.30 ± 0.51, 2.62 ± 0.36, and T/N ratio of 2.2 ± 1.3, 22.6 ± 6.6, 23.7 ± 8.3, 20.2 ± 3.8 for primary lower grade glioma (LGG), primary glioblastoma (GBM), recurrent diffuse glioma and metastatic brain tumor, respectively. Primary GBM showed significantly higher SUVmax, SUVmean and T/N ratio than primary LGG (p = 0.015-0.032). Meanwhile, 1 gliosis and 1 stable disease were also included and exhibited minimum FBY activity, with SUVmax of 0.17 and 0.33, T/N ratio of 1.04 and 2.58, respectively.Elevated FBY activity can be seen in most malignant brain tumors, and primary GBM, recurrent glioma and metastatic brain tumor displayed significant tumor to background ratio, which may facilitate the malignancy stratification and future boron neutron capture therapy.