Amino Acid PET Research Articles

Functional connectivity between tumor region and resting-state networks as imaging biomarker for overall survival in recurrent gliomas diagnosed by FET PET

Abstract Background Amino acid PET using the tracer O-(2-[18F]fluoroethyl)-L-tyrosine (FET) is one of the most reliable imaging methods for detecting glioma recurrence. Here, we hypothesized that functional MR connectivity between the metabolic active recurrent tumor region and resting-state networks of the brain could serve as a prognostic imaging biomarker for overall survival (OS). Methods The study included 82 patients (26-81 years; median ECOG performance score, 0) with recurrent gliomas following therapy (WHO-CNS 2021 grade 4 glioblastoma, n=57; grade 3 or 4 astrocytoma, n=12; grade 2 or 3 oligodendroglioma, n=13) diagnosed by FET PET simultaneously acquired with functional resting-state MR. Functional connectivity (FC) was assessed between tumor regions and seven canonical resting-state networks. Results WHO tumor grade and IDH mutation status were strong predictors of OS after recurrence (p<0.001). Overall FC between tumor regions and networks was highest in oligodendrogliomas and was inversely related to tumor grade (p=0.031). FC between the tumor region and the dorsal attention network was associated with longer OS (HR, 0.88; 95%CI, 0.80-0.97; p=0.007), and showed an independent association with OS (HR, 0.90; 95%CI, 0.81-0.99; p=0.033) in a model including clinical factors, tumor volume and MGMT. In the glioblastoma subgroup, tumor volume and FC between tumor and the visual network (HR, 0.90; 95%CI, 0.82-0.99, p=0.031) were independent predictors of survival. Conclusion Recurrent gliomas exhibit significant FC to resting-state networks of the brain. Besides tumor type and grade, high FC between the tumor and distinct networks could serve as independent prognostic factors for improved OS in these patients.

Borderline Findings in O-(2-[18F]-Fluoroethyl)-l-Tyrosine PET of Patients with Suspected Glioma Relapse: Role in Clinical Practice.

One of the most common clinical indications for amino acid PET using the tracer O-(2-[18F]-fluoroethyl)-l-tyrosine (18F-FET) is the differentiation of tumor relapse from treatment-related changes in patients with gliomas. A subset of patients may present with an uptake of 18F-FET close to recommended threshold values. The goal of this study was to investigate the frequency of borderline cases and the role of quantitative 18F-FET PET parameters in this situation. Methods: We retrospectively identified 439 patients with pretreated gliomas who underwent 18F-FET PET for suspected tumor relapse and in whom the final diagnoses were confirmed by histopathology (n = 175) or clinical course (n = 264). Two experienced nuclear medicine physicians, masked to the final diagnoses, evaluated visually the PET scans by consensus. The findings were classified into 3 categories: clearly positive findings, borderline findings, or clearly negative findings. The diagnostic performance of established 18F-FET PET parameters (i.e., tumor-to-brain ratio [TBR], time-to-peak ratio, slope, intercept) was evaluated separately for these 3 groups using receiver operating characteristics analyses. Results: In the visual analysis, 18F-FET uptake was classified as clearly negative in 67 patients (15%), clearly positive in 234 patients (53%), and borderline in 136 patients (31%), with averaged mean TBR values of 1.5, 2.3, and 1.9, respectively. Receiver operating characteristics analysis showed a high accuracy for TBR values in patients rated as clearly positive or negative in visual rating (area under curve [AUC], 0.84-0.86), whereas the diagnostic performance of TBR values in borderline cases according to visual analysis was significantly lower (AUC, <0.60). Using TBR values ± 10% above or below the cutoff values increased the AUC by approximately 10% (AUC, 0.82-0.84). Conclusion: A considerable number of patients may present with borderline findings in 18F-FET PET. In these patients, quantitative parameters should be used with caution for decision-making. The use of TBR values above or below the range of the cutoff values ±10% may increase the reliability of quantitative parameters to differentiate between tumor relapse and treatment-related changes.

The Value of Multidisciplinary Neuro-oncological Tumor Boards to Increase the Accuracy of FET PET for Identifying Brain Tumor Relapse.

Especially in Europe, amino acid PET is increasingly integrated into multidisciplinary neuro-oncological tumor boards (MNTBs) to overcome diagnostic uncertainties such as treatment-related changes. We evaluated the accuracy of MNTB decisions that included the O-(2-[18F]-fluoroethyl)-L-tyrosine (FET) PET information compared with FET PET results alone to differentiate tumor relapse from treatment-related changes. In a single academic center, we retrospectively evaluated 180 MNTB decisions of 151 patients with CNS WHO grade 3 or 4 gliomas (n = 122) or brain metastases (n = 29) presenting equivocal MRI findings following anticancer treatment. All patients underwent FET PET imaging besides MRI before MNTB discussion. Additionally, the patient's clinical status and pretreatment were considered for decision-making. The diagnostic performance was calculated for FET PET findings alone and MNTB decisions that included FET PET results using 2 × 2 contingency tables. MNTB decisions were validated using the neuropathological result in 43% (n = 78) or clinicoradiologically in 57% (n = 102). FET PET results alone yielded an accuracy of 87% (sensitivity, 90%; specificity, 65%; positive predictive value, 95%). When integrating FET PET results for decision-making in the MNTB setting, the accuracy increased to 95% (sensitivity, 99%; specificity, 70%; positive predictive value, 96%; P = 0.002). In MNTB decisions concerning glioblastoma patients, the median survival was 2.4 times longer when FET PET suggested treatment-related changes (15.6 vs 6.4 months; P = 0.009). Our results suggest that MNTB discussion further enhances the FET PET value for identifying brain tumor relapse. A prospective evaluation of FET PET results with and without integration in an MNTB is warranted.

Flip-flop phenomenon on dual SSTR PET and amino acid PET in a case of recurrent meningioma with malignant transformation.

Flip-flop phenomenon on dual SSTR PET and amino acid PET in a case of recurrent meningioma with malignant transformation.

CNSC-16. ASSOCIATION BETWEEN RESTING-STATE-NETWORK FUNCTIONAL CONNECTIVITY AND SURVIVAL IN RECURRENT GLIOMAS DIAGNOSED USING FET PET

Abstract BACKGROUND Functional connectivity between glioma-infiltrated brain tissue and remote cortical regions has been linked to overall survival (OS) in patients with newly diagnosed glioblastoma. We studied the association of functional connectivity between tumor and resting-state networks and OS in patients with recurrent gliomas. PATIENTS AND METHODS The study included 82 patients (26-81 years; median ECOG performance score, 0) with recurrent gliomas (grade 4 glioblastoma, n=57; grade 3 and 4 astrocytoma, n=12; grade 2 and 3 oligodendroglioma, n=13) who had undergone first-line therapy. Diagnosis of recurrence was confirmed by amino acid PET using the tracer O-(2-[18F]-fluoroethyl)-L-tyrosine (FET). FET PET and resting-state functional MRI were simultaneously acquired on a 3T hybrid PET/MR scanner. We performed a seed-based dual regression analysis to determine the functional connectivity between metabolically active tumors and seven canonical resting state networks. RESULTS Average functional connectivity was highest in oligodendrogliomas (z-score, 6.9±1.9) and was inversely related to the tumor grade (p=0.031). Univariate Cox regression analysis revealed a significant (p&amp;lt;0.05) positive association between OS and tumor connectivity with the visual, somatomotor, and dorsal attention networks. Subsequent stepwise multivariate Cox regression analysis refined this association to the dorsal attention network alone (HR, 0.88; 95% CI, 0.80-0.97; p=0.007). Patients with the highest functional connectivity (z-score&amp;gt;8.3, n=21) had a median OS of 31.4 months, while those with the lowest functional connectivity (z-score&amp;lt;4.3, n=21) had 10.6 months. Functional connectivity between tumors and the dorsal attention network showed an independent association with OS (HR, 0.90; 95% CI, 0.81-0.99; p=0.033) in a multivariate model, including various prognostic factors. CONCLUSION Recurrent gliomas exhibit significant functional connectivity to most of the major known resting-state networks, highest in oligodendrogliomas. The data suggest that high functional connectivity between the tumor and the dorsal attention network is an independent prognostic factor for improved OS.

NIMG-48. MEASURABLE DISEASE AS BASELINE CRITERION FOR RESPONSE ASSESSMENT IN GLIOBLASTOMA TRIALS – A COMPARATIVE STUDY OF MRI-BASED (RANO 2.0) VERSUS PET-BASED (PET RANO 1.0) ASSESSMENT

Abstract Response assessment in glioblastoma relies on measuring contrast enhancement on MRI according to RANO 2.0 criteria, and ‘measurable disease’ often serves as inclusion criterion for clinical trials. Recently, criteria based on amino acid PET have been proposed for response assessment in clinical trials (PET RANO 1.0). Here, we compare ‘measurable disease’ as defined by PET RANO 1.0 with the standard MRI-based RANO 2.0 criteria in glioblastoma patients. In this retrospective single-center study, we identified patients with newly diagnosed IDH-wildtype glioblastoma who underwent [18F]FET PET and MRI after resection or biopsy and before chemoradiotherapy. Two independent investigators analyzed ‘measurable disease’ according to PET RANO 1.0 versus MRI-based RANO 2.0 criteria. Additionally, lesion size and uptake intensity, including maximal and mean target-to-background ratio, were assessed. We evaluated 136 patients with 76 cases after biopsy and 60 after microsurgical resection. Using RANO 2.0, 35/76 patients (46.1%) had measurable disease in the biopsy group, and 25/60 (41.6%) in the resected group (median sum of maximum cross-sectional diameters: 39.7mm and 28.0mm, respectively). Utilizing PET RANO 1.0, a significantly higher proportion (overall 123/136, 90.4%; 66/76 (86.8%) after biopsy; 57/60 (95.0%) after resection) had measurable disease (p&amp;lt;0.001). None of the 10 patients in the biopsy group nor of the 3 patients in the resected group without measurable disease on PET had measurable disease on MRI. Contrariwise, 32/41 patients (73.2%) in the biopsy group and 30/35 (85.7%) in the resected group without measurable disease on MRI exhibited measurable disease on PET. PET RANO 1.0 identifies a significantly higher number of patients with ‘measurable disease’ compared to conventional MRI-based criteria in the perioperative period of glioblastoma. PET-based assessment may thus serve as a novel baseline parameter for evaluating treatment response in glioblastoma trials, that may allow the enrollment of larger patient populations. Further validation in prospective trials is warranted.

BIOM-44.18F-DOPA-PET THRESHOLDS FOR BOTH NEWLY DIAGNOSED AND RECURRENT ASTROCYTOMA USING PATHOLOGICAL GROUPING OF SPATIALLY CORRELATED BIOPSIES

Abstract BACKGROUND Glioma radiotherapy planning requires accurate tumor delineation. While T1- contrast-enhanced-MRI (T1-CE-MRI) is the standard, due to blood-brain-barrier breakdown dependencies, T1-CE-MRI fails to reflect the extent of glioma. Studies using amino acid PET tracers report glioma uptake up to 3cm-4cm beyond T1-CE. In this study, amino acid tracer 18F-fluoro-dihydroxyphenylalanine (18F-DOPA) uptake was correlated with histopathological features to determine tumor thresholds. METHODS Using registered 18F-DOPA-PET and T1-CE-MRI images in the Stealth Neuronavigation system targeting concordant and discordant regions, 181 stereotactic biopsy samples (newly-diagnosed=74; recurrent=107) were obtained from 59 enrolled astrocytoma patients across two prospective phase II clinical trials between 2010-2019. An experienced neuropathologist reviewed each sample with hematoxylin and eosin stain and assigned an alphanumeric score: mitotic activity (0=no tumor; 1=no mitosis; 2=few/scattered mitosis; 3=frequent mitosis) and cellular density (A=&amp;lt;25%; B=25%-50%; C=50%-75%; D=&amp;gt;75%). Samples assigned 1C-1D, 2B-2D, or 3A-3D were categorized as histopathological high-score (aggressive disease), remaining samples as low-score. Relative mean (rFDOPA_mean) tumor-to-background uptake ratios were computed for 5mm uniformly expanded volumes from each Stealth biopsy coordinate using the crescent and wedge normalization methods. Relative uptake was compared overall and separately within newly-diagnosed/recurrent disease subgroups. An optimal rFDOPA_mean threshold to delineate high- from low-score was determined using the maximal Youden index of ROC curves. RESULTS Overall, high-score samples (n=116) had higher median (IQR) rFDOPA_mean uptake than low-score samples (n=65): high-score rFDOPA:mean=1.70(1.16-2.26), low-score rFDOPA:mean=1.16(0.83-1.49), Kruskal-Wallis p&amp;lt;0.001. The uptake difference between high- vs. low-score samples was observed within newly-diagnosed and recurrent subgroups, but was only significant for newly-diagnosed (p&amp;lt;0.001). For newly-diagnosed, an rFDOPA:mean=1.49 cutoff between high- and low-score groups shows 69% accuracy, 63% sensitivity, 80% specificity (AUC=0.782). Using the wedge normalization method, rFDOPA_mean values were 0.2 higher than crescent method values. CONCLUSIONS This work presents histologically verified 18F-DOPA-PET thresholds for aggressive disease in newly-diagnosed astrocytoma patients. Separate thresholds will need to be determined for recurrent glioma patients.

P13.01.A 11C-METHIONIN PET FOR RADIOTHERAPY TREATMENT PLANNING IN PATIENTS WITH RAPID EARLY PROGRESSION AFTER GLIOBLASTOMA SURGERY: PROSPECTIVE PHASE II TRIAL

Abstract BACKGROUND Radiotherapy (RT) is a standard treatment for nearly all glioblastoma patients following initial surgery. Few retrospective studies indicate negative prognostic instances of progression during the planning magnetic resonance (MR) (up to 1 week before initiating RT), termed Rapid Early Progression (REP). The optimal RT management for REP patients remains uncertain. The objective of this prospective phase II trial (NCT05608395) is to assess impact of 11C-Methionine PET used for RT planning in REP glioblastoma patients. It is one of the first prospective clinical interventional trials focused on this specific cohort of patients. MATERIAL AND METHODS We enrolled glioblastoma, IDHwt, or Astrocytoma, IDHmt, WHO grade IV patients, who developed REP characterized by 1) increase in postoperative residuum by ≥ 25%, 2) appearance of new contras enhancing lesion, 3) unequivocal progression of the unresected satelite. Patients received treatment based on the Stupp or Perry protocol. Treatment response was evaluated using RANO criteria. RT target volumes were delineated as follows: Gross tumor volume included tumor cavity, enhancing lesion and 11C-MET PET (1.3 tumor-to-background ratio). The clinical target volume was GTV plus a modified 2cm margin reflecting surrounding organs at risk. Volumetric analyses of different radiotherapy target volume were performed using EclipseTM software including patterns of failure. RESULTS During 12/2020 - 12/2023, total of 31 patients were enrolled (16 treated via abbreviated RT course); median age 60 years, ECOG 0-1 in 28 patients, median follow up 20 months. No effect of 11C-MET PET - based radiotherapy treatment planning of GBM patients with REP was observed on PFS (median 3.4 months comparing to 4.9 in historical control cohort) and OS (12.3 months comparing to 15.7 months). Median MET volume was 7.3cm3 (43% of MRI volume), MET avidity was presented in 7 patients et least 1cm beyond MRI volume. Central recurrence was presented in 87% patients. CONCLUSION The optimal treatment of patients with REP is unknown and needs to be studied in more details including dose escalation studies with reduced target margins potentialy directed also by aminoacid PET examination. Adjustment of target radiotherapy volumes using 11C-MET PET did not lead to improved PFS or OS. Supported by NU20-03-00148.

18F]DOPA PET for lesion definition and contouring using different thresholds in patients with gliomas.

Amino-acid (AA) PET has recently been endorsed by the ESTRO-EANO guidelines for RT-planning in glioblastomas, with recommended lesion-to-brain-ratio thresholds (1.6-1.8) derived from a biopsy-controlled FET-PET study. We aimed to compare target definition at [18F]DOPA-PET between the ESTRO-EANO thresholds and other biological-tumor-volume (BTV) thresholds (derived from the striatum) typically used in [18F]DOPA-PET. A retrospective analysis was conducted on glioma patients scanned with [18F]DOPA-PET/CT at our center between April 2021 and January 2024. 3D BTV was semi-automatically computed using a dedicated workstation (Philips HealthCare) with four thresholds: 1.6xSUV<inf>mean</inf> of background, 1.8xSUV<inf>mean</inf> of background, SUV<inf>mean</inf> and SUV<inf>max</inf> of the contralateral striatum. The delineation accuracy of different thresholds was visually evaluated and a t-test was used to compare the different VOIs volumes (0.05 significance-level). 50 patients were included (36 previously received surgery). Volume definition based on the striatum SUV<inf>max</inf> was significantly smaller compared to other thresholds (2.1 cm3), resulting in inaccurate VOIs at visual inspection in 21/50 patients. No significant differences were highlighted in BTV defined based on 1.6 or 1.8xSUV<inf>mean</inf> of background (15.7 vs. 12.7 cm3; VOIs accurate in 49/50 and 46/50 patients, respectively). BTV based on striatum SUV<inf>mean</inf> was significantly smaller compared to the 1.6xSUV<inf>mean</inf> threshold only in surgically-treated patients (P=0.04), while no significant differences were highlighted compared to the 1.8xSUV<inf>mean</inf> threshold regardless of the patients' group. The ESTRO-EANO FET-PET thresholds proved to be interchangeable in patients scanned with [18F]DOPA-PET, while the use of a threshold based on the contralateral-striatum SUV<inf>mean</inf> provided partially overlapping results prompting further investigation.

PET imaging of gliomas: Status quo and quo vadis?

PET imaging, particularly using amino acid tracers, has become a valuable adjunct to anatomical MRI in the clinical management of patients with glioma. Collaborative international efforts have led to the development of clinical and technical guidelines for PET imaging in gliomas. The increasing readiness of statutory health insurance agencies, especially in European countries, to reimburse amino acid PET underscores its growing importance in clinical practice. Integrating artificial intelligence and radiomics in PET imaging of patients with glioma may significantly improve tumor detection, segmentation, and response assessment. Efforts are ongoing to facilitate the clinical translation of these techniques. Considerable progress in computer technology developments (eg quantum computers) may be helpful to accelerate these efforts. Next-generation PET scanners, such as long-axial field-of-view PET/CT scanners, have improved image quality and body coverage and therefore expanded the spectrum of indications for PET imaging in Neuro-Oncology (eg PET imaging of the whole spine). Encouraging results of clinical trials in patients with glioma have prompted the development of PET tracers directing therapeutically relevant targets (eg the mutant isocitrate dehydrogenase) for novel anticancer agents in gliomas to improve response assessment. In addition, the success of theranostics for the treatment of extracranial neoplasms such as neuroendocrine tumors and prostate cancer has currently prompted efforts to translate this approach to patients with glioma. These advancements highlight the evolving role of PET imaging in Neuro-Oncology, offering insights into tumor biology and treatment response, thereby informing personalized patient care. Nevertheless, these innovations warrant further validation in the near future.

The role of [18F]FDOPA PET as an adjunct to conventional MRI in the diagnosis of aggressive glial lesions.

Amino acid PET is recommended for the initial diagnosis of brain lesions, but its value for identifying aggressive lesions remains to be established. The current study therefore evaluates the added-value of dynamic [18F]FDOPA PET as an adjunct to conventional MRI for determining the aggressiveness of presumed glial lesions at diagnosis. Consecutive patients, with a minimal 1 year-follow-up, underwent contrast-enhanced MRI (CE MRI) and dynamic [18F]FDOPA PET to characterize their suspected glial lesion. Lesions were classified semi-automatically by their CE MRI (MRI-/+), and PET parameters (static tumor-to-background ratio, TBR; dynamic time-to-peak ratio, TTPratio). Diagnostic accuracies of MRI and PET parameters for the differentiation of tumor aggressiveness were evaluated by chi-square test or receiver operating characteristic analyses. Aggressive lesions were either defined as lesions with dismal molecular characteristics based on the WHO 2021 classification of brain tumors or with compatible clinico-radiological profiles. Time-to-treatment failure (TTF) and overall survival (OS) were evaluated. Of the 109 patients included, 46 had aggressive lesions (45 confirmed by histo-molecular analyses). CE MRI identified aggressive lesions with an accuracy of 73%. TBRmax (threshold of 3.2), and TTPratio (threshold of 5.4min) respectively identified aggressive lesions with an accuracy of 83% and 76% and were independent of CE MRI and clinical factors in the multivariate analysis. Among the MRI-lesions, 11/56 (20%) were aggressive and respectively 55% and 50% of these aggressive lesions showed high TBRmax and short TTPratio in PET. High TBRmax and short TTPratio in PET were significantly associated to poorer survivals (p ≤ 0.009). Dynamic [18F]FDOPA PET provides a similar diagnostic accuracy as contrast enhancement in MRI to identify the aggressiveness of suspected glial lesions at diagnosis. Both methods, however, are complementary and [18F]FDOPA PET may be a useful additional tool in equivocal cases.

Amino-acid PET as a prognostic tool after post Stupp protocol temozolomide therapy in high-grade glioma patients

PurposeThis study aimed to evaluate the prognostic performance of amino-acid PET in high-grade gliomas (HGG) patients at the time of temozolomide (TMZ) treatment discontinuation, after the Stupp protocol.MethodsThe analysis included consecutive HGG patients with dynamic [18F]FDOPA PET imaging within 3 months of the end of TMZ therapy, post-Stupp protocol. Static and dynamic PET parameters, responses to RANO criteria for MRI and clinical and histo-molecular factors were correlated to progression-free (PFS).ResultsThirty-two patients (59.4 [54.0;67.6] years old, 13 (41%) women) were included. Static PET parameters peak tumor-to-background ratio and metabolic tumor volume (respective thresholds of 1.9 and 1.5 mL) showed the best 84% accuracies for predicting PFS at 6 months (p = 0.02). These static PET parameters were also independent predictor of PFS in multivariate analysis (p ≤ 0.05).ConclusionIn HGG patients having undergone a Stupp protocol, the absence of significant PET uptake after TMZ constitutes a favorable prognostic factor.

Preferred Imaging for Target Volume Delineation for Radiotherapy of Recurrent Glioblastoma: A Literature Review of the Available Evidence.

Recurrence in glioblastoma lacks a standardized treatment, prompting an exploration of re-irradiation's efficacy. A comprehensive systematic review from January 2005 to May 2023 assessed the role of MRI sequences in recurrent glioblastoma re-irradiation. The search criteria, employing MeSH terms, targeted English-language, peer-reviewed articles. The inclusion criteria comprised both retrospective and prospective studies, excluding certain types and populations for specificity. The PICO methodology guided data extraction, and the statistical analysis employed Chi-squared tests via MedCalc v22.009. Out of the 355 identified studies, 81 met the criteria, involving 3280 patients across 65 retrospective and 16 prospective studies. The key findings indicate diverse treatment modalities, with linac-based photons predominating. The median age at re-irradiation was 54 years, and the median time interval between radiation courses was 15.5 months. Contrast-enhanced T1-weighted sequences were favored for target delineation, with PET-imaging used in fewer studies. Re-irradiation was generally well tolerated (median G3 adverse events: 3.5%). The clinical outcomes varied, with a median 1-year local control rate of 61% and a median overall survival of 11 months. No significant differences were noted in the G3 toxicity and clinical outcomes based on the MRI sequence preference or PET-based delineation. In the setting of recurrent glioblastoma, contrast-enhanced T1-weighted sequences were preferred for target delineation, allowing clinicians to deliver a safe and effective therapeutic option; amino acid PET imaging may represent a useful device to discriminate radionecrosis from recurrent disease. Future investigations, including the ongoing GLIAA, NOA-10, ARO 2013/1 trial, will aim to refine approaches and standardize methodologies for improved outcomes in recurrent glioblastoma re-irradiation.

Preoperative 11 C-Methionine PET-MRI in Pediatric Infratentorial Tumors.

MRI is the main imaging modality for pediatric brain tumors, but amino acid PET can provide additional information. Simultaneous PET-MRI acquisition allows to fully assess the tumor and lower the radiation exposure. Although symptomatic posterior fossa tumors are typically resected, the patient management is evolving and will benefit from an improved preoperative tumor characterization. We aimed to explore, in children with newly diagnosed posterior fossa tumor, the complementarity of the information provided by amino acid PET and MRI parameters and the correlation to histopathological results. Children with a newly diagnosed posterior fossa tumor prospectively underwent a preoperative 11 C-methionine (MET) PET-MRI. Images were assessed visually and semiquantitatively. Using correlation, minimum apparent diffusion coefficient (ADC min ) and contrast enhancement were compared with MET SUV max . The diameter of the enhancing lesions was compared with metabolic tumoral volume. Lesions were classified according to the 2021 World Health Organization (WHO) classification. Ten children were included 4 pilocytic astrocytomas, 2 medulloblastomas, 1 ganglioglioma, 1 central nervous system embryonal tumor, and 1 schwannoma. All lesions showed visually increased MET uptake. A negative moderate correlation was found between ADC min and SUV max values ( r = -0.39). Mean SUV max was 3.8 (range, 3.3-4.2) in WHO grade 4 versus 2.5 (range, 1.7-3.0) in WHO grade 1 lesions. A positive moderate correlation was found between metabolic tumoral volume and diameter values ( r = 0.34). There was no correlation between SUV max and contrast enhancement intensity ( r = -0.15). Preoperative 11 C-MET PET and MRI could provide complementary information to characterize pediatric infratentorial tumors.

Advanced Imaging in the Diagnosis and Response Assessment of High-Grade Glioma: AJR Expert Panel Narrative Review.

This AJR Expert Panel Narrative explores the current status of advanced MRI and PET techniques for the post-therapeutic response assessment of high-grade adult-type gliomas, focusing on ongoing clinical controversies in current practice. Discussed techniques that complement conventional MRI and aid the differentiation of recurrent tumor from post-treatment effects include DWI and diffusion tensor imaging; perfusion MRI techniques including dynamic susceptibility contrast (DSC), dynamic contrast-enhanced MRI, and arterial spin labeling; MR spectroscopy including assessment of 2-hydroxyglutarate (2HG) concentration; glucose- and amino acid (AA)-based PET; and amide proton transfer imaging. Updated criteria for Response Assessment in Neuro-Oncology are presented. Given the abundant supporting clinical evidence, the panel supports a recommendation that routine response assessment after HGG treatment should include perfusion MRI, particularly given the development of a consensus recommended DSC-MRI protocol. Although published studies support 2HG MRS and AA PET, these techniques' widespread adoption will likely require increased availability (for 2HG MRS) or increased insurance funding in the United States (for AA PET). The article concludes with a series of consensus opinions from the author panel, centered on the clinical integration of the advanced imaging techniques into posttreatment surveillance protocols.

Example of Artificial Intelligence-Based Decision Support for Amino Acid PET: Early Prediction of Suspected Brain Tumor Foci for Patient Management.

Example of Artificial Intelligence-Based Decision Support for Amino Acid PET: Early Prediction of Suspected Brain Tumor Foci for Patient Management.

Amino acid PET vs. RANO MRI for prediction of overall survival in patients with recurrent high grade glioma under bevacizumab therapy.

To summarize evidence on the comparative value of amino acid (AA) PET and conventional MRI for prediction of overall survival (OS) in patients with recurrent high grade glioma (rHGG) under bevacizumab therapy. Medical databases were screened for studies with individual data on OS, follow-up MRI, and PET findings in the same patient. MRI images were assessed according to the RANO criteria. A receiver operating characteristic curve analysis was used to predict OS at 9 months. Five studies with a total of 72 patients were included. Median OS was significantly lower in the PET-positive than in the PET-negative group. PET findings predicted OS with a pooled sensitivity and specificity of 76% and 71%, respectively. Corresponding values for MRI were 32% and 82%. Area under the curve and sensitivity were significantly higher for PET than for MRI. For monitoring of patients with rHGG under bevacizumab therapy, AA-PET should be preferred over RANO MRI.

Measure what is measurable: PET RANO 1.0 criteria for interpretation of amino acid PET of diffuse gliomas.

Measure what is measurable: PET RANO 1.0 criteria for interpretation of amino acid PET of diffuse gliomas.

11C]-methionine positron emission tomography in the evaluation of pediatric low-grade gliomas.

[11C]-Methionine positron emission tomography (PET; [11C]-MET-PET) is principally used for the evaluation of brain tumors in adults. Although amino acid PET tracers are more commonly used in the evaluation of pediatric brain tumors, data on [11C]-MET-PET imaging of pediatric low-grade gliomas (pLGG) is scarce. This study aimed to investigate the roles of [11C]-MET-PET in the evaluation of pLGGs. Eighteen patients with newly diagnosed pLGG and 26 previously treated pLGG patients underwent [11C]-MET-PET met the inclusion and exclusion criteria. Tumor-to-brain uptake ratio (TBR) and metabolic tumor volumes were assessed for diagnostic performances (newly diagnosed, 15; previously treated 26), change with therapy (newly diagnosed, 9; previously treated 7), and variability among different histology (n = 12) and molecular markers (n = 7) of pLGGs. The sensitivity of [11C]-MET-PET for diagnosing pLGG, newly diagnosed, and previously treated combined was 93% for both TBRmax and TBRpeak, 76% for TBRmean, and 95% for qualitative evaluation. TBRmax showed a statistically significant reduction after treatment, while other PET parameters showed a tendency to decrease. Median TBRmax, TBRpeak, and TBRmean values were slightly higher in the BRAFV600E mutated tumors compared to the BRAF fused tumors. Median TBRmax, and TBRpeak in diffuse astrocytomas were higher compared to pilocytic astrocytomas, but median TBRmean, was slightly higher in pilocytic astrocytomas. However, formal statistical analysis was not done due to the small sample size. Our study shows that [11C]-MET-PET reliably characterizes new and previously treated pLGGs. Our study also shows that quantitative parameters tend to decrease with treatment, and differences may exist between various pLGG types.

Imaging challenges: Immunotherapy's influence on the diagnostic accuracy of amino acid PET in suspected progressive brain metastases

Imaging challenges: Immunotherapy's influence on the diagnostic accuracy of amino acid PET in suspected progressive brain metastases