¹⁸F-FGln PET/CT guided surgical biopsy and resection in patient with brain tumors

Purpose: MRI alone has its limitations for target selection in biopsy or resection in newly diagnosed and pretreated pediatric brain tumor patients. ¹⁸F-(2S, 4R) 4-fluoroglutamine (¹⁸F-FGln) PET imaging is considered to identify metabolically active glioma tissue. We retrospectively analyzed our experience with ¹⁸F-FGln-PET in targeted surgical interventions for brain tumors.

Methods: In 46 cases with lesions suspicious of a growing brain tumor on MRI, either newly diagnosed or after antitumoral treatment led to ¹⁸F-FGln-PET imaging for target selection prior to stereotactic biopsy, navigated open biopsy or navigated microsurgical tumor resection. Indications for ¹⁸F-FGln-PET imaging were visualization of metabolic active tumor tissue within diffuse tumors or pretreated lesions as well as depicting their extent and characteristics. Histopathologic diagnoses were made in all cases (21 high-grade gliomas, 14 metastases to the brain, 3 lymphomas, 2 germ cell tumors, 2 necrotic tissue after radiotherapy, 2 meningeomas, 1 hemangioblastoma and 1schwannoma).

Results: ¹⁸F-FGln-PET integration in surgery was feasible in all patients using stereotaxy or neuronavigation. Sensitivity for tumor detection was 42/46(SUVmax>1.5). ¹⁸F-FGln-PET was false positive in two pretreated patients. Differences in SUVmax between high-grade gliomas (5.18±1.14), metastases (3.11±1.68), and primary brain lymphomas (7.01±1.39) were significant (P < 0.05). These differences were also significant at pairwise analysis. The time activity curve (TAC) of dynamic ¹⁸F-FGln PET/CT in the three groups of malignant tumors show that lymphomas with a rapid increase in the early phase (0~5min.pi), and a consistent in the middle (5~15min.pi) and late phase (15~30min.pi); the high-grade gliomas with a low level in the initial phase, a slow increase in the middle and late phase; the metastases with a slow increase in the first and middle phase, and a consistent in late phase.

Conclusions: ¹⁸F-FGln-PET imaging is helpful for target selection and can be integrated in surgical guidance. ¹⁸F-FGln-PET image-guided surgical targeting yielded histological diagnosis with decent specificity and high sensitivity in brain tumor patients. Our results warrant further evaluation of ¹⁸F-FET-PET imaging for surgical guidance. High-grade gliomas, metastases, and lymphomas may be distinguished on the basis of measured ¹⁸F-FGln uptake and TAC. Higher uptake of ¹⁸F-FGln is a significant feature of primary brain lymphomas.