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FET PET in the evaluation of indeterminate brain lesions on MRI: Differentiating glioma from other non-neoplastic
David L Chan1, Edward Hsiao2, Geoff Schembri2
1Department of Nuclear Medicine, Royal North Shore Hospital, St Leonards, NSW, Australia; Department of Medical Oncology, Royal North Shore Hospital, St Leonards, NSW, Australia.
Abstract:
We aimed to determine the utility of FET PET in the management of indeterminate CNS lesions found on MRI. We performed a retrospective analysis of patients with FET PET at a single tertiary institution from 2011 to 2015. FET PET images were processed using usual methods and measurements taken including SUVmax, TBRmax, and analysis of dynamic series where available (Kipeak, Vdpeak, as well as tumor:background ratio for these variables). Correlation studies were performed using ANOVA between cohorts of high-grade histology, low-grade histology, and benign histology/stable on observation. Thirty-five patients were included, of whom 34 were suitable for analysis with median follow-up of 5 months. The positive predictive value of FET PET in this cohort was 83.3%. FET SUVmax differentiated between patients with high-grade (mean SUV 3.38, 95% CI 2.21-4.55), low-grade (1.88, 95% CI 1.33-2.43) and benign/observation (1.42, 95% CI 1.13-1.71) cohorts (p = 0.0003). Similarly, tumour to brain ratio was significant (p < 0.0001). Kipeak distinguished between high grade and observation cohorts (p = 0.036), as did KiTBR (p = 0.025). Vd peak was not significantly different in these two cohorts (p = 0.057) but Vd TBR was (p = 0.041). In conclusion, FET PET demonstrated a high positive predictive value for glioma in patients with indeterminate brain lesions on MRI. The combination of negative FET and negative FDG PET scans may predict an indolent clinical course. Confirmatory trials are needed to establish the potential value of FET PET in guiding surgical management in this cohort.
Insights
Fluorine-18-FET PET imaging shows high accuracy in managing indeterminate brain lesions, differentiating glioma grades. Negative scans may indicate a slow-growing tumor, but further trials are needed.
Area of Science:
- Neuroimaging
- Oncology
- Nuclear Medicine
Background:
- Magnetic Resonance Imaging (MRI) can detect indeterminate Central Nervous System (CNS) lesions.
- Distinguishing between high-grade glioma, low-grade glioma, and benign lesions is crucial for patient management.
- Positron Emission Tomography (PET) with O-(2-[18F]fluoroethyl)-L-tyrosine (FET) is a promising imaging modality.
Purpose of the Study:
- To evaluate the utility of FET PET in the management of indeterminate CNS lesions identified on MRI.
- To assess the positive predictive value of FET PET for glioma.
- To determine if FET PET parameters can differentiate between different grades of CNS lesions and benign entities.
Main Methods:
- Retrospective analysis of 35 patients with indeterminate CNS lesions who underwent FET PET imaging.
- Measurements included Standardized Uptake Value (SUVmax), Tumor-to-Brain Ratio (TBRmax), and dynamic parameters (Kipeak, Vdpeak, KiTBR, VdTBR).
- Correlation studies using ANOVA were performed between high-grade, low-grade, and benign histology cohorts.
Main Results:
- FET PET demonstrated a positive predictive value of 83.3% for glioma.
- FET SUVmax and TBRmax significantly differentiated between high-grade, low-grade, and benign/observation cohorts (p < 0.001).
- Dynamic parameters like Kipeak and KiTBR also showed significant differences between high-grade and observation groups.
Conclusions:
- FET PET is a valuable tool with high positive predictive value for identifying glioma in patients with indeterminate brain lesions on MRI.
- Negative FET PET, especially in conjunction with negative FDG PET, may suggest an indolent clinical course.
- Further confirmatory trials are necessary to establish FET PET's role in guiding surgical management.
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