Re-evaluation of the diagnostic performance of 11C-methionine PET/CT according to the 2016 WHO classification of cerebral gliomas

Integration of amide proton transfer-weighted imaging and methionine positron emission tomography histogram parameters enhances the prediction of isocitrate dehydrogenase mutations in adult diffuse gliomas

BACKGROUND

To evaluate whether the combination of amide proton transfer-weighted imaging (APT-WI) and methionine positron emission tomography (MET-PET) enhances the non-invasive prediction of isocitrate dehydrogenase (IDH) mutation status in adult diffuse gliomas.

RESULTS

We retrospectively analysed 28 adult patients with histologically confirmed diffuse gliomas who underwent preoperative APT-WI and MET-PET imaging at our institution. Histogram analyses were conducted for both imaging modalities, extracting parameters such as the 10th, 50th, 70th, and 90th percentiles, mean, variance, skewness, and kurtosis. Parameters between IDH-mutant and IDH-wildtype gliomas were compared using the Mann-Whitney U test. Diagnostic performance was assessed using receiver operating characteristic (ROC) curve analysis, and combined models of the two parameters were constructed using multivariable logistic regression. IDH-wildtype gliomas exhibited significantly higher APT-WI 90th percentile (APT90) values (median: 3.51%, interquartile range [IQR]: 1.92-4.23%) compared to IDH-mutant gliomas (median: 2.24%, IQR: 1.52-2.85%, p = 0.039). Similarly, IDH-wildtype gliomas showed elevated MET-PET maximum tumour-to-normal ratios (TNRmax) (median: 2.51, IQR: 2.13-3.41) compared to IDH-mutant gliomas (median: 1.62, IQR: 1.30-2.77, p = 0.020). ROC curve analysis indicated that the combined model of APT90 and TNR kurtosis achieved an area under the curve of 0.85, demonstrating superior diagnostic accuracy compared to that of single-parameter models.

CONCLUSIONS

Combining histogram-derived parameters from APT-WI and MET-PET significantly improves the diagnostic accuracy for predicting IDH mutation status in diffuse gliomas. This non-invasive approach may serve as a valuable adjunct for preoperative evaluation and the development of personalised treatment strategies in patients with gliomas.

Efficient Detection of Oligodendroglioma With 1p/19q Codeletion Mutation via Methionine PET Imaging: A Promising Diagnostic Approach

Background Oligodendrogliomas are a distinct subtype of gliomas frequently characterized by the 1p/19q codeletion and isocitrate dehydrogenase (IDH) gene mutations, both associated with improved therapeutic response and prolonged survival. These genetic alterations modulate the transsulfuration pathway, leading to increased methionine uptake by tumor cells. Positron emission tomography (PET) with 11C-labeled methionine (MET PET) leverages these metabolic changes, providing a noninvasive means to distinguish oligodendrogliomas and predict the 1p/19q codeletion presence. This study evaluates the diagnostic potential of MET PET in detecting 1p/19q deletions and quantifying SUV max (maximum standardized uptake value) to evaluate metabolic activity in newly diagnosed oligodendrogliomas, emphasizing the value of advanced imaging in guiding targeted clinical management. Methods We performed a retrospective chart review of pediatric and adult patients treated between 1999 and 2010, a period selected to capture evolving clinical protocols and advancements in imaging techniques. This timeframe maximized data availability and provided a longitudinal perspective on how shifts in diagnostic and therapeutic strategies may have influenced outcomes. All participants underwent MET PET scans and subsequent oligodendroglioma resections, with follow-up data extending until 2010. Relevant information, including demographics, clinical details, and glioma-specific mutations, was extracted from clinical records. Cases without histological confirmation or missing genetic results (1p/19q codeletion, IDH) were excluded to safeguard data integrity and limit bias. Both univariate and multivariate linear regression analyses were employed to assess the relationship between MET PET findings (SUV max) and these genetic alterations, aiming to clarify the predictive value of PET imaging in tumor genetics. Results Among the 85 oligodendroglioma patients analyzed (median age 50 ± 3 years), 47.1% (n = 40) harbored the 1p/19q codeletion, whereas 52.9% (n = 45) did not. The median SUV max was significantly higher in patients lacking the codeletion (3.7, IQR: 2.9-4.4) than in those with it (2.2, IQR: 1.8-2.6; p < 0.001). A Mann-Whitney U test confirmed the discrepancy (U = 189, z = -6.261, p < 0.0001). Further analysis using a multiple linear regression model indicated that the absence of the 1p/19q codeletion and an elevated Ki-67 index collectively predicted higher SUV max (F(1, 82) = 10.43, p < 0.0001), accounting for approximately 42.2% of the variability in SUV max. Conclusions The findings from this study underscore the utility of the MET PET scan not only as a diagnostic tool for identifying the presence of the 1p/19q deletion in patients with oligodendrogliomas but also for evaluating tumor metabolism through SUV max measurements. The scan's ability to distinguish tumor from necrosis based on metabolic activity enhances its clinical value, providing critical insights for optimal patient management. The data suggest that patients with higher SUV max are more likely to lack the 1p/19q deletion, a finding that could significantly influence treatment decisions and prognostic assessments. Given these results, MET PET scans represent a potent tool in refining diagnostic and follow-up strategies for oligodendroglioma, guiding more targeted and effective therapeutic approaches.

Association Between Pretreatment 11C-Methionine Positron Emission Tomography Metrics, Histology, and Prognosis in 125 Newly Diagnosed Patients with Adult-Type Diffuse Glioma Based on the World Health Organization 2021Classification

OBJECTIVE

To clarify the relationships between 11C-methionine (MET) positron emission tomography (PET) metrics and the histology, genetics, and prognosis of adult-type diffuse glioma (ADG) based on the World Health Organization (WHO) 2021 classification.

METHODS

A total of 125 newly diagnosed patients with ADG were enrolled. We compared the maximum standardized uptake value (SUVmax), tumor-to-normal background ratio (TNR), metabolic tumor volume (MTV), and total lesion methionine uptake (TLMU) to the histology and genetics of the patients with ADG. We also evaluated the prognoses of the 93 surgically treated patients.

RESULTS

The patients with isocitrate dehydrogenase wild ADG showed significantly higher MET-PET metrics (P < 0.05 for all parameters), significantly shorter overall survival and progression-free survival (P < 0.0001 for both) than those of the patients with isocitrate dehydrogenase mutant (IDHm) ADG. In the IDHm ADG group, the SUVmax, MTV, and TLMU values were significantly higher in patients with IDHm grade (G) 4 astrocytoma than patients with IDHm G2/3 astrocytoma (P < 0.05 for all), but not than patients with G2-3 oligodendroglioma. The progression-free survival was significantly shorter in the patients with G4 astrocytoma versus the patients with G2/3 astrocytoma and G3 oligodendroglioma (P < 0.05 for both). The SUVmax and TNR values were significantly higher in recurrent patients than nonrecurrent patients (P < 0.01 for both), but no significant differences were found in MTV or TLMU values.

CONCLUSIONS

MET-PET metrics well reflect the histological subtype, WHO grade and prognosis of ADG based on the 2021 WHO classification, with the exception of oligodendroglial tumors. Volumetric parameters were not significantly associated with recurrence, unlike the SUVmax and TNR.

Recent Update on PET/CT Radiotracers for Imaging Cerebral Glioma

Positron emission tomography/computed tomography (PET/CT) has dramatically altered the landscape of noninvasive glioma evaluation, offering complementary insights to those gained through magnetic resonance imaging (MRI). PET/CT scans enable a multifaceted analysis of glioma biology, supporting clinical applications from grading and differential diagnosis to mapping the full extent of tumors and planning subsequent treatments and evaluations. With a broad array of specialized radiotracers, researchers and clinicians can now probe various biological characteristics of gliomas, such as glucose utilization, cellular proliferation, oxygen deficiency, amino acid trafficking, and reactive astrogliosis. This review aims to provide a recent update on the application of versatile PET/CT radiotracers in glioma research and clinical practice.

EANM practice guidelines for an appropriate use of PET and SPECT for patients with epilepsy

Epilepsy is one of the most frequent neurological conditions with an estimated prevalence of more than 50 million people worldwide and an annual incidence of two million. Although pharmacotherapy with anti-seizure medication (ASM) is the treatment of choice, ~30% of patients with epilepsy do not respond to ASM and become drug resistant. Focal epilepsy is the most frequent form of epilepsy. In patients with drug-resistant focal epilepsy, epilepsy surgery is a treatment option depending on the localisation of the seizure focus for seizure relief or seizure freedom with consecutive improvement in quality of life. Beside examinations such as scalp video/electroencephalography (EEG) telemetry, structural, and functional magnetic resonance imaging (MRI), which are primary standard tools for the diagnostic work-up and therapy management of epilepsy patients, molecular neuroimaging using different radiopharmaceuticals with single-photon emission computed tomography (SPECT) and positron emission tomography (PET) influences and impacts on therapy decisions. To date, there are no literature-based praxis recommendations for the use of Nuclear Medicine (NM) imaging procedures in epilepsy. The aims of these guidelines are to assist in understanding the role and challenges of radiotracer imaging for epilepsy; to provide practical information for performing different molecular imaging procedures for epilepsy; and to provide an algorithm for selecting the most appropriate imaging procedures in specific clinical situations based on current literature. These guidelines are written and authorized by the European Association of Nuclear Medicine (EANM) to promote optimal epilepsy imaging, especially in the presurgical setting in children, adolescents, and adults with focal epilepsy. They will assist NM healthcare professionals and also specialists such as Neurologists, Neurophysiologists, Neurosurgeons, Psychiatrists, Psychologists, and others involved in epilepsy management in the detection and interpretation of epileptic seizure onset zone (SOZ) for further treatment decision. The information provided should be applied according to local laws and regulations as well as the availability of various radiopharmaceuticals and imaging modalities.

11 C-Acetate PET/CT for Reactive Astrogliosis Outperforms 11 C-Methionine PET/CT in Glioma Classification and Survival Prediction

PURPOSE

11 C-acetate (ACE) PET/CT visualizes reactive astrogliosis in tumor microenvironment. This study compared 11 C-ACE and 11 C-methionine (MET) PET/CT for glioma classification and predicting patient survival.

PATIENTS AND METHODS

In this prospective study, a total of 142 patients with cerebral gliomas underwent preoperative MRI, 11 C-MET PET/CT, and 11 C-ACE PET/CT. Tumor-to-contralateral cortex (TNR MET ) and tumor-to-choroid plexus ratios (TNR ACE ) were calculated for 11 C-MET and 11 C-ACE. The Kruskal-Wallis test and Bonferroni post hoc analysis were used to compare the differences in 11 C-TNR MET and 11 C-TNR ACE . The Cox proportional hazards regression analysis and classification and regression tree models were used to assess progression-free survival (PFS) and overall survival (OS).

RESULTS

The median 11 C-TNR MET and 11 C-TNR ACE for oligodendrogliomas (ODs), IDH1 -mutant astrocytomas, IDH1 -wildtype astrocytomas, and glioblastomas were 2.75, 1.40, 2.30, and 3.70, respectively, and 1.40, 1.20, 1.77, and 2.87, respectively. The median 11 C-TNR MET was significantly different among the groups, except between ODs and IDH1 -wildtype astrocytomas, whereas the median 11 C-TNR ACE was significantly different among all groups. The classification and regression tree model identified 4 risk groups ( IDH1 -mutant with 11 C-TNR ACE ≤ 1.4, IDH1 -mutant with 11 C-TNR ACE > 1.4, IDH1 -wildtype with 11 C-TNR ACE ≤ 1.8, and IDH1 -wildtype with 11 C-TNR ACE > 1.8), with median PFS of 52.7, 44.5, 25.9, and 8.9 months, respectively. Using a 11 C-TNR ACE cutoff of 1.4 for IDH1 -mutant gliomas and a 11 C-TNR ACE cutoff of 2.0 for IDH1 -wildtype gliomas, all gliomas were divided into 4 groups with median OS of 52.7, 46.8, 27.6, and 12.0 months, respectively. Significant differences in PFS and OS were observed among the 4 groups after correcting for multiple comparisons.

CONCLUSIONS

11 C-ACE PET/CT is better for glioma classification and survival prediction than 11 C-MET PET/CT, highlighting its potential role in cerebral glioma patients.

[PET/CT with 11C-methionine as a predictor of disease-free survival in patients with IDH1 wild type diffuse glioma]

Prognosis of IDH (IDHwt) wild-type gliomas is worse compared to IDH-mutant tumors regardless of histological criteria for glioblastoma. However, there is still uncertainty regarding favorable course of disease and predictors of long-term survival in IDHwt gliomas.

OBJECTIVE

To study the metabolic characteristics of IDH1wt diffuse astrocytomas using 11C-methionine PET/CT and prognostic significance of PET-associated parameters for disease-free survival.

MATERIAL AND METHODS

We analyzed 79 adults with IDH1wt diffuse gliomas. Quantitative analysis consisted of 11C-methionine accumulation index and metabolic tumor volume. Kaplan-Meier and Cox analyses were used to determine prognostic significance of histological findings and PET parameters.

RESULTS

Glioblastoma and astrocytoma grade 2 or 3 were diagnosed in 41% and 59% of patients, respectively. Accumulation index significantly differed between astrocytomas grade 2 and 3 (p=0.03). Significant predictors of disease-free survival were age, histological type of astrocytoma and tumor grade, contrast enhancement, PET-associated biomarkers (accumulation index and metabolic tumor volume) and compliance of metabolic pattern with glioblastoma syndrome (p<0.05). Disease-free survival >24 months was established for age <41 years, maximum accumulation index <1.64, tumor accumulation index <1.39 and metabolic tumor volume <13.44 cm3. In multivariate Cox analysis, independent predictors of disease-free survival were age and PET syndrome of glioblastoma.

CONCLUSION

Diffuse IDH1wt gliomas are a heterogeneous group differing in metabolic characteristics and prognosis. PET/CT with 11C-methionine may be effective for stratifying patients into groups with unfavorable and favorable prognosis, as well as assessment of advisability of in-depth searching for IDH1/IDH2 mutation.

Predictive IDH Genotyping Based on the Evaluation of Spatial Metabolic Heterogeneity by Compartmental Uptake Characteristics in Preoperative Glioma Using 18F-FET PET

Molecular markers are of increasing importance for classifying, treating, and determining the prognosis for central nervous system tumors. Isocitrate dehydrogenase (IDH) is a critical regulator of glucose and amino acid metabolism. Our objective was to investigate metabolic reprogramming of glioma using compartmental uptake (CU) characteristics in O-(2-18F-fluoroethyl)-l-tyrosine (FET) PET and to evaluate its diagnostic potential for IDH genotyping. Methods: Between 2017 and 2022, patients with confirmed glioma were preoperatively investigated using static 18F-FET PET. Metabolic tumor volume (MTV), MTV for 60%-100% uptake (MTV60), and T2-weighted and contrast-enhancing lesion volumes were automatically segmented using U-Net neural architecture and isocontouring. Volume intersections were determined using the Dice coefficient. Uptake characteristics were determined for metabolically defined compartments (central [80%-100%] and peripheral [60%-75%] areas of 18F-FET uptake). CU ratio was defined as the fraction between the peripheral and central compartments. Mean target-to-background ratio was calculated. Comparisons were performed using parametric and nonparametric tests. Receiver-operating-characteristic curves, regression, and correlation were used for statistical analysis. Results: In total, 52 participants (male, 27, female, 25; mean age ± SD, 51 ± 16 y) were evaluated. MTV60 was greater and distinct from contrast-enhancing lesion volume (P = 0.046). IDH-mutated tumors presented a greater volumetric CU ratio and SUV CU ratio than IDH wild-type tumors (P < 0.05). Volumetric CU ratio determined IDH genotype with excellent diagnostic performance (area under the curve [AUC], 0.88; P < 0.001) at more than 5.49 (sensitivity, 86%, specificity, 90%), because IDH-mutated tumors presented a greater peripheral metabolic compartment than IDH wild-type tumors (P = 0.045). MTV60 and MTV were not suitable for IDH classification (P > 0.05). SUV CU ratio (AUC, 0.72; P = 0.005) and target-to-background ratio (AUC, 0.68; P = 0.016) achieved modest diagnostic performance-inferior to the volumetric CU ratio. Furthermore, the classification of loss of heterozygosity of chromosomes 1p and 19q (AUC, 0.75; P = 0.019), MGMT promoter methylation (AUC, 0.70; P = 0.011), and ATRX loss (AUC, 0.73; P = 0.004) by amino acid PET was evaluated. Conclusion: We proposed parametric 18F-FET PET as a noninvasive metabolic biomarker for the evaluation of CU characteristics, which differentiated IDH genotype with excellent diagnostic performance, establishing a critical association between spatial metabolic heterogeneity, mitochondrial tricarboxylic acid cycle, and genomic features with critical implications for clinical management and the diagnostic workup of patients with central nervous system cancer.

The prognostic power of [11C]methionine PET in IDH-wildtype diffuse gliomas with lower-grade histological features: venturing beyond WHO classification

PURPOSE

IDH-wildtype (IDH-wt) diffuse gliomas with histological features of lower-grade gliomas (LGGs) are rare and heterogeneous primary brain tumours. [11C]Methionine (MET) positron emission tomography (PET) is commonly used to evaluate glial neoplasms at diagnosis. The present study aimed to assess the prognostic value of MET PET in newly diagnosed, treatment naïve IDH-wt gliomas with histological features of LGGs.

METHODS

Patients with a histological diagnosis of IDH-wt LGG who underwent preoperative (< 100 days) MET PET/CT and surgery were retrospectively included. Qualitative and semi-quantitative analyses of MET PET images were performed. Progression-free survival (PFS) and overall survival (OS) were analysed by Kaplan-Meier curves. Cox proportional-hazards regression was used to test the association of imaging and clinical data to PFS and OS.

RESULTS

We included 48 patients (M:F = 25:23; median age 55). 39 lesions were positive and 9 negative at MET PET. Positive MET PET was significantly associated with shorter median PFS (15.7 months vs. not reached, p = 0.0146) and OS time (32.6 months vs. not reached, p = 0.0253). Incomplete surgical resection and higher TBRmean values were independent predictors of shorter PFS on multivariate analysis (p < 0.001 for both). Higher tumour grade and incomplete surgical resection were independent predictors of OS at multivariate analysis (p = 0.027 and p = 0.01, respectively).

CONCLUSION

MET PET is useful for the prognostic stratification of patients with IDH-wt glial neoplasms with histological LGGs features. Considering their huge biological heterogeneity, the combination of MET PET and molecular analyses may help to improve the prognostic accuracy in these diffuse gliomas subset and influence therapeutic choices accordingly.

Metabolic kinetic modeling of [11C]methionine based on total-body PET in multiple myeloma

PURPOSE

Multiple myeloma (MM) is a malignant disease characterized by the secretion of monoclonal immunoglobulins and has a high demand for amino acids. [11C]methionine total-body PET is capable of noninvasive dynamic monitoring of radiotracer in vivo, thus providing a way to reveal the dynamic changes of myeloma metabolism. This study aims to analyze the metabolic process of [11C]methionine based on kinetic modeling, and to preliminary reveal its application value in MM.

METHODS

Dynamic total-body [11C]methionine PET/CT was conducted with uEXPLORER in 12 subjects (9 MM patients and 3 controls). The tissue time activity curves (TACs) of organs and bone marrows were extracted. Model fitting of TACs was operated using PMOD Kinetic Modeling. After validation by Goodness of fit (GOF), the reversible two-tissue compartment model (2T4k) was used to further analysis. R software was used to analyze the correlation between kinetic parameters and clinical indicators.

RESULTS

The 2T4k has passed the criterion of GOF and was used to fit the data of 0-20 minutes. The [11C]methionine net uptake rate (Ki) was significantly higher in the MM lesions than in the non-myeloma controls (control: 0.040±0.007 mL/g/min, MM: 0.171±0.108 mL/g/min, p=0.009). The Ki values were found to be correlated with M protein levels in MM patients. MM patients with t(4;14) translocations had an elevated k4 value compared with t(4;14) negative patients.

CONCLUSION

MM lesions have a propensity for uptake of [11C]methionine. The serum levels of M protein are correlated with [11C]methionine uptake rate in myeloma. Metabolic classification based on the k4 value may be a promising strategy for risk stratification in MM.

Differentiation of astrocytoma between grades II and III using a combination of methionine positron emission tomography and magnetic resonance spectroscopy

Objective

This study aimed to establish a method for differentiating between grades II and III astrocytomas using preoperative imaging.

Methods

We retrospectively analyzed astrocytic tumors, including 18 grade II astrocytomas (isocitrate dehydrogenase (IDH)-mutant: IDH-wildtype = 8:10) and 56 grade III anaplastic astrocytomas (37:19). We recorded the maximum methionine (MET) uptake ratios (tumor-to-normal: T/N) on positron emission tomography (PET) and three MRS peak ratios: choline (Cho)/creatine (Cr), N-acetyl aspartate (NAA)/Cr, and Cho/NAA, between June 2015 and June 2020. We then evaluated the cut-off values to differentiate between grades II and III. We compared the grading results between contrast enhancement effects on MR and combinational diagnostic methods (CDM) on a scatter chart using the cutoff values of the T/N ratio and MRS parameters.

Results

The IDH-mutant group showed significant differences in the Cho/NAA ratio between grades II and III using univariate analysis; however, multiple regression analysis results negated this. The IDH-wildtype group showed no significant differences between the groups. Contrast enhancement effects also showed no significant differences in IDH status. Accordingly, regardless of the IDH status, no statistically independent factors differentiated between grades II and III. However, CDMs showed higher sensitivity and negative predictive value in distinguishing them than MRI contrast examinations for both IDH statuses. We demonstrated a significantly higher diagnostic rate of grade III than of grade II with CDM, which was more striking in the IDH-mutant group than in the wild-type group.

Conclusions

CDM could be valuable in differentiating between grade II and III astrocytic tumors.

Amino Acid Tracer PET MRI in Glioma Management: What a Neuroradiologist Needs to Know

PET with amino acid tracers provides additional insight beyond MR imaging into the biology of gliomas that can be used for initial diagnosis, delineation of tumor margins, planning of surgical and radiation therapy, assessment of residual tumor, and evaluation of posttreatment response. Hybrid PET MR imaging allows the simultaneous acquisition of various PET and MR imaging parameters in a single investigation with reduced scanning time and improved anatomic localization. This review aimed to provide neuroradiologists with a concise overview of the various amino acid tracers and a practical understanding of the clinical applications of amino acid PET MR imaging in glioma management. Future perspectives in newer advances, novel radiotracers, radiomics, and cost-effectiveness are also outlined.

Clinical applications and prospects of PET imaging in patients with IDH-mutant gliomas

PET imaging using radiolabeled amino acids in addition to MRI has become a valuable diagnostic tool in the clinical management of patients with brain tumors. This review provides a comprehensive overview of PET studies in glioma patients with a mutation in the isocitrate dehydrogenase gene (IDH). A considerable fraction of these tumors typically show no contrast enhancement on MRI, especially when classified as grade 2 according to the World Health Organization classification of Central Nervous System tumors. Major diagnostic challenges in this situation are differential diagnosis, target definition for diagnostic biopsies, delineation of glioma extent for treatment planning, differentiation of treatment-related changes from tumor progression, and the evaluation of response to alkylating agents. The main focus of this review is the role of amino acid PET in this setting. Furthermore, in light of clinical trials using IDH inhibitors targeting the mutated IDH enzyme for treating patients with IDH-mutant gliomas, we also aim to give an outlook on PET probes specifically targeting the IDH mutation, which appear potentially helpful for response assessment.

11 C-Acetate PET/CT Detects Reactive Astrogliosis Helping Glioma Classification

PURPOSE

11 C-acetate ( 11 C-ACE) uptake on PET/CT was recently discovered to represent reactive astrocytes in the tumor microenvironment. This study aimed at evaluating the role of 11 C-ACE PET/CT as an imaging biomarker of reactive astrogliosis in characterizing different types of gliomas.

METHODS

In this prospective study, a total of 182 patients underwent 11 C-ACE PET/CT before surgery. The ratio of SUV max of a glioma to the SUV mean of the contralateral choroid plexus ( 11 C-ACE TCR) on PET/CT was calculated. 11 C-ACE TCRs were compared with the World Health Organization grades and isocitrate dehydrogenase 1 ( IDH1 ) mutation status. Grade 2 was considered low-grade tumor, and grades 3 and 4 were considered high-grade tumors.

RESULTS

The median 11 C-ACE TCR was significantly higher in IDH1 wild-type (wt) tumors (n = 91) than in IDH1 -mutant (mt) tumors (n = 91) (2.38 vs 1.30, P < 0.001). Of the 91 IDH1 -mt tumors, there were no differences in the median 11 C-ACE TCRs between oligodendrogliomas (ODs) and astrocytic tumors (1.40 vs 1.20, P > 0.05). In grading low- versus high-grade gliomas, the receiver operating characteristic curve analyses showed a higher area under the curve (0.951) in IDH1 -wt tumors than in IDH1 -mt tumors (0.783, P = 0.002). Grade 2 ODs were well differentiated from high-grade gliomas. The 11 C-ACE TCR of grade 3 ODs was significantly lower than that of IDH1 -wt glioblastomas.

CONCLUSIONS

High 11 C-ACE uptake is associated with high-grade IDH1 -wt tumors, thus facilitating differentiation from high-grade IDH1-mt and low-grade gliomas. In particular, low 11 C-ACE uptake in ODs is advantageous in overcoming the limitation of radiolabeled amino acid tracers.

Facts and Fictions About [18F]FDG versus Other Tracers in Managing Patients with Brain Tumors: It Is Time to Rectify the Ongoing Misconceptions

MRI is the first-choice imaging technique for brain tumors. Positron emission tomography can be combined together with multiparametric MRI to increase diagnostic confidence. Radiolabeled amino acids have gained wide clinical acceptance. The reported pooled specificity of [¹⁸F]FDG positron emission tomography is high and [¹⁸F]FDG might still be the first-choice positron emission tomography tracer in cases of World Health Organization grade 3 to 4 gliomas or [¹⁸F]FDG-avid tumors, avoiding the use of more expensive and less available radiolabeled amino acids. The present review discusses the additional value of positron emission tomography with a focus on [¹⁸F]FDG and radiolabeled amino acids.

Role of Molecular Imaging with PET/MR Imaging in the Diagnosis and Management of Brain Tumors

Gliomas are the most common primary brain tumors. Hybrid PET/MR imaging has revolutionized brain tumor imaging, allowing for noninvasive, simultaneous assessment of morphologic, functional, metabolic, and molecular parameters within the brain. Molecular information obtained from PET imaging may aid in the detection, classification, prognostication, and therapeutic decision making for gliomas. ¹⁸F-fluorodeoxyglucose (FDG) has been widely used in the setting of brain tumor imaging, and multiple techniques may be employed to optimize this methodology. More recently, a number of non-¹⁸F-FDG-PET radiotracers have been applied toward brain tumor imaging and are used in clinical practice.

Preoperative [11C]methionine PET to personalize treatment decisions in patients with lower-grade gliomas

BACKGROUND

PET with radiolabelled amino acids is used in the preoperative evaluation of patients with glial neoplasms. This study aimed to assess the role of [ 11C]methionine (MET) PET in assessing molecular features, tumour extent, and prognosis in newly-diagnosed lower-grade gliomas (LGGs) surgically treated.

METHODS

153 patients with a new diagnosis of grade 2/3 glioma who underwent surgery at our Institution and were imaged preoperatively using [ 11C]MET PET/CT were retrospectively included. [ 11C]MET PET images were qualitatively and semiquantitatively analyzed using tumour-to-background ratio (TBR). Progression-free survival (PFS) rates were estimated using the Kaplan-Meier method and Cox proportional-hazards regression was used to test the association of clinicopathological and imaging data to PFS.

RESULTS

Overall, 111 lesions (73%) were positive, while thirty-two (21%) and ten (6%) were isometabolic and hypometabolic at [ 11C]MET PET, respectively. [ 11C]MET uptake was more common in oligodendrogliomas than IDH-mutant astrocytomas (87% vs 50% of cases, respectively). Among [ 11C]MET-positive gliomas, grade 3 oligodendrogliomas had the highest median TBRmax (3.22). In 25% of patients, PET helped to better delineate tumour margins compared to MRI only. In IDH-mutant astrocytomas, higher TBRmax values at [ 11C]MET PET were independent predictors of shorter PFS.

CONCLUSIONS

This work highlights the role of preoperative [ 11C]MET PET in estimating the type, assessing tumour extent, and predicting biological behaviour and prognosis of LGGs. Our findings support the implementation of [ 11C]MET PET in routine clinical practice to better manage these neoplasms.

60 Years of Achievements by KSNM in Neuroimaging Research

Nuclear medicine neuroimaging is able to show functional and molecular biologic abnormalities in various neuropsychiatric diseases. Therefore, it has played important roles in the clinical diagnosis and in research on the normal and pathological states of the brain. More than 400 outstanding studies have been conducted by Korean researchers over the past 60 years. In the 1990s, when multiheaded single-photon emission computed tomography (SPECT) scanners were first introduced in South Korea, stroke research using brain perfusion SPECT was conducted. With the spread of positron emission tomography (PET) scanners in the 2000s, research on the clinical usefulness of PET and the evaluation of pathophysiology in various diseases such as epilepsy, brain tumors, degenerative brain diseases, and other neuropsychiatric diseases were actively conducted using [¹⁸F]FDG and various neuroreceptor tracers. In the 2010s, with the clinical application of new radiopharmaceuticals for amyloid and tau imaging, research demonstrating the clinical usefulness of PET imaging and the pathophysiology of dementia has increased rapidly. It is expected that the role of nuclear medicine will expand with the development of new radiopharmaceuticals and analysis technologies, along with the application of artificial intelligence for early and differential diagnosis, and the development of therapeutic agents for degenerative brain diseases.

Case Report: Detection of Symptomatic Treatment-Related Changes in a Patient With Anaplastic Oligodendroglioma Using FET PET

Following local and systemic treatment of gliomas, the differentiation between glioma relapse and treatment-related changes such as pseudoprogression or radiation necrosis using conventional MRI is limited. To overcome this limitation, various amino acid PET tracers such as O-[2-(¹⁸F)-fluoroethyl]-L-tyrosine (FET) are increasingly used and provide valuable additional clinical information. We here report neuroimaging findings in a clincally symptomatic 53-year-old woman with a recurrent anaplastic oligodendroglioma with MRI findings highly suspicious for tumor progression. In contrast, FET PET imaging suggested treatment-related changes considerably earlier than the regression of contrast enhancement on MRI. In patients with oligodendroglioma, the phenomenon of symptomatic treatment-related changes is not well described, making these imaging findings unique and important for clinical decision-making.

Fractal analysis of 11C-methionine PET in patients with newly diagnosed glioma

Background

The present study tested the possible utility of fractal analysis from l-[methyl-¹¹C]-methionine (MET) uptake in patients with newly diagnosed gliomas for differentiating glioma, especially in relation to isocitrate dehydrogenase 1 (IDH1) mutation status, and as compared with the conventional standardized uptake value (SUV) parameters.

Methods

Investigations of MET PET/CT were performed retrospectively in 47 patients with newly diagnosed glioma. Tumors were divided into three groups: lower grade glioma (IDH1-mutant diffuse astrocytoma and IDH1-mutant anaplastic astrocytoma), higher grade glioma (IDH1-wildtype diffuse astrocytoma and IDH1-wildtype anaplastic astrocytoma), and glioblastoma. The fractal dimension for tumor, maximum SUV (SUVmax) for tumor (T) and mean SUV for normal contralateral hemisphere (N) were calculated, and the tumor-to-normal (T/N) ratio was determined. Metabolic tumor volume (MTV) and total lesion MET uptake (TLMU) were also measured.

Results

There were significant differences in SUVmax (p = 0.006) and T/N ratio (p = 0.02) between lower grade glioma and glioblastoma. There were no significant differences among any of the three groups in MTV or TLMU. Significant differences were obtained in the fractal dimension between lower grade glioma and higher grade glioma (p = 0.006) and glioblastoma (p < 0.001).

Conclusions

The results of this preliminary study in a small patient population suggest that the fractal dimension using MET PET in patients with newly diagnosed gliomas is useful for differentiating glioma, especially in relation to IDH1 mutation status, which has not been possible with SUV parameters.

Glycolysis on F-18 FDG PET/CT Is Superior to Amino Acid Metabolism on C-11 Methionine PET/CT in Identifying Advanced Renal Cell Carcinoma at Staging

Simple Summary

Alteration of metabolism, including glycolysis and glutaminolysis in malignant tumours, has become a hallmark of cancer and related biological aggressiveness. The metabolic signature of each cancer has been actively investigated for potential new drug development. Of the metabolic imaging biomarkers, F-18 fluorodeoxyglucose (FDG) and C-11 methionine positron emission tomography/computed tomography (PET/CT) are widely studied to evaluate the degree of glucose metabolism and amino acid metabolism, respectively. In this prospective study, we found that both F-18 FDG and C-11 methionine uptakes on PET/CT were heterogeneous in renal cell carcinomas, and increased uptake was associated with higher grades of both radiotracers. Additionally, metabolic tumour volume on F-18 FDG PET/CT but not C-11 methionine PET/CT was significant in predicting advanced-stage renal cell carcinoma. These metabolic features derived with PET/CT may help in the development of new drugs targeting glucose and amino acid metabolic pathways.

Abstract

We evaluated the value of F-18 fluorodeoxyglucose (FDG) and C-11 methionine positron emission tomography/computed tomography (PET/CT) to predict high-Fuhrman grade and advanced-stage tumours in patients with renal cell carcinoma (RCC). Forty patients with RCC underwent F-18 FDG and C-11 methionine PET/CT between September 2016 and September 2018. They were classified into limited (stages I and II, n = 15) or advanced stages (stages III and IV, n = 25) according to pathological staging. Logistic regressions were used to predict the advanced stage using various parameters, including maximum standardised uptake value (SUV_max) and metabolic tumour volume (MTV). Receiver operating characteristic analyses were performed to predict high-grade tumours (Fuhrman 3 and 4). On univariate analysis, tumour size, SUV_max and MTV of F-18 FDG and C-11 methionine, and Fuhrman grades were significant predictors for the advanced stage. On multivariate analysis, F-18 FDG MTV > 21.3 cm³ was the most significant predictor (p < 0.001). The area under the curve for predicting high-grade tumours was 0.830 for F-18 FDG (p < 0.001) and 0.726 for C-11 methionine PET/CT (p = 0.014). In conclusion, glycolysis on F-18 FDG PET/CT and amino acid metabolism on C-11 methionine PET/CT were variable but increased in high-grade RCCs. Increased MTV on F-18 FDG PET/CT is a powerful predictor of advanced-stage tumours.

Diagnostic Performance of [11C]Methionine Positron Emission Tomography in Newly Diagnosed and Untreated Glioma Based on the Revised World Health Organization 2016 Classification

BACKGROUND

The relationship between uptake of amino acid tracer with positron emission tomography (PET) and glioma subtypes/gene status is still unclear.

OBJECTIVE

To assess the relationship between uptake of [¹¹C]methionine using PET and pathology, IDH (isocitrate dehydrogenase) mutation, 1p/19q codeletion, and TERT (telomerase reverse transcriptase) promoter status in gliomas.

METHODS

The participants were 68 patients with newly diagnosed and untreated glioma who underwent surgical excision and preoperative [¹¹C]methionine PET examination at Osaka City University Hospital between July 2011 and March 2018. Clinical and imaging studies were reviewed retrospectively based on the medical records at our institution.

RESULTS

The mean lesion/contralateral normal brain tissue (L/N) ratio of diffuse astrocytomas was significantly lower than that of anaplastic astrocytomas (P = 0.00155), glioblastoma (P < 0.001), and oligodendrogliomas (P = 0.0157). The mean L/N ratio of IDH mutant gliomas was significantly lower than that of IDH wild-type gliomas (median 1.75 vs. 2.61; P = 0.00162). A mean L/N ratio of 2.05 provided the best sensitivity and specificity for distinguishing between IDH mutant and IDH wild-type gliomas (69.2% and 76.2%, respectively). The mean L/N ratio of TERT promoter mutant gliomas was significantly higher than that of TERT promoter wild-type gliomas (P = 0.0147). Multiple regression analysis showed that pathologic diagnosis was the only influential factor on L/N ratio.

CONCLUSIONS

Distinguishing glioma subtypes based on the revised 2016 World Health Organization classification of the central nervous system tumors on the basis of [¹¹C]methionine PET alone seems to be difficult. However, [¹¹C]methionine PET might be useful for predicting the IDH mutation status in newly diagnosed and untreated gliomas noninvasively before tumor resection.

Hypoxia and Amino Acid Imaging of High-Grade Glioma: 18F-FAZA PET/CT and 11C-Methionine PET/MRI

In the present case, we report the first experience of a patient with high-grade glioma who underwent dual F-FAZA PET/CT imaging for intratumoral hypoxia assessment, before treatment, and for therapy monitoring in the suspicious of recurrence, as part of a clinical research protocol. In addition, despite the diagnosis of glioblastoma, the patient at 3 years from diagnosis was alive and underwent C-methionine simultaneous PET/MRI for disease monitoring after treatment, showing stability of disease. The multitracer capability of PET in assessing different and complementary metabolic features along with the use of a last-generation scanner as PET/MRI in brain oncology are here enlighten.

A Nomogram Modeling 11C-MET PET/CT and Clinical Features in Glioma Helps Predict IDH Mutation

Purpose: We developed a ¹¹C-Methionine positron emission tomography/computed tomography (¹¹C-MET PET/CT)-based nomogram model that uses easy-accessible imaging and clinical features to achieve reliable non-invasive isocitrate dehydrogenase (IDH)-mutant prediction with strong clinical translational capability.

Methods: One hundred and ten patients with pathologically proven glioma who underwent pretreatment ¹¹C-MET PET/CT were retrospectively reviewed. IDH genotype was determined by IDH1 R132H immunohistochemistry staining. Maximum, mean and peak tumor-to-normal brain tissue (TNRmax, TNRmean, TNRpeak), metabolic tumor volume (MTV), total lesion methionine uptake (TLMU), and standard deviation of SUV (SUV_SD) of the lesions on MET PET images were obtained via a dedicated workstation (Siemens. syngo.via). Univariate and multivariate logistic regression models were used to identify the predictive factors for IDH mutation. Nomogram and calibration plots were further performed.

Results: In the entire population, TNRmean, TNRmax, TNRpeak, and SUV_SD of IDH-mutant glioma patients were significantly lower than these values of IDH wildtype. Receiver operating characteristic (ROC) analysis suggested SUV_SD had the best performance for IDH-mutant discrimination (AUC = 0.731, cut-off ≤ 0.29, p < 0.001). All pairs of the ¹¹C-MET PET metrics showed linear associations by Pearson correlation coefficients between 0.228 and 0.986. Multivariate analyses demonstrated that SUV_SD (>0.29 vs. ≤ 0.29 OR: 0.053, p = 0.010), dichotomized brain midline structure involvement (no vs. yes OR: 26.52, p = 0.000) and age (≤ 45 vs. >45 years OR: 3.23, p = 0.023), were associated with a higher incidence of IDH mutation. The nomogram modeling showed good discrimination, with a C-statistics of 0.866 (95% CI: 0.796–0.937) and was well-calibrated.

Conclusions:¹¹C-Methionine PET/CT imaging features (SUV_SD and the involvement of brain midline structure) can be conveniently used to facilitate the pre-operative prediction of IDH genotype. The nomogram model based on ¹¹C-Methionine PET/CT and clinical age features might be clinically useful in non-invasive IDH mutation status prediction for untreated glioma patients.

Glucose Loading Enhances the Value of 18F-FDG PET/CT for the Characterization and Delineation of Cerebral Gliomas

This study aimed to assess how to enhance the value of ¹⁸F-Fluorodeoxyglucose (FDG) PET/CTs for glioma grading and better delineation of the tumor boundary by glucose loading. In mouse models of brain tumor using U87MG cells, ¹⁸F-FDG-PET images were obtained after fasting and after glucose loading. There was a significant difference in the tumor-to-normal cortex-uptake ratio (TNR) between the fasting and glucose-loading scans. ¹⁴C-2-Deoxy-D-glucose (¹⁴C-DG) uptake was measured in vitro using U87MG, U373MG and primary neurons cultured with different concentrations of glucose. The tumor-to-neuron ratio of ¹⁴C-DG uptake increased with up to 10 mM of glucose. Finally, 10 low-grade and 17 high-grade glioma patients underwent fasting and glucose loading ¹⁸F-FDG PET/CT and the TNR was compared between scans. The effect of glucose loading was significant in high-grade but not in low-grade gliomas. The receiver operating characteristic curve analyses with a cut-off TNR of 0.81 showed a higher area under the curve after glucose loading than fasting for differentiating low-grade versus high-grade gliomas. In addition, the glucose loading PET/CT was more useful than the fasting PET/CT for the discrimination of oligodendrogliomas from IDH-wildtype glioblastomas. Glucose loading resulted in a greater reduction in ¹⁸F-FDG uptake in the normal cortex than in tumors, which increases the usefulness of ¹⁸F-FDG PET/CT for grading.

Diagnostic value of PET/CT with 11C-methionine (MET) and 18F-fluorothymidine (FLT) in newly diagnosed glioma based on the 2016 WHO classification

Background

The molecular features of isocitrate dehydrogenase (IDH) mutation and chromosome 1p and 19q (1p/19q) codeletion status have pivotal role for differentiating gliomas and have been integrated in the World Health Organization (WHO) classification in 2016. Positron emission tomography (PET) with 3′-deoxy-3′-[¹⁸F]fluorothymidine (FLT) has been used to evaluate tumour grade and proliferative activity and compared with l-[methyl-¹¹C]-methionine (MET) in glioma patients. Herein, we evaluated tracer uptakes of MET-PET/CT and FLT-PET/CT for differentiating glioma based on the 2016 WHO classification especially in relation to IDH1 mutation status.

Methods

In total, 81 patients with newly diagnosed supratentorial glioma were enrolled in this study. They underwent PET/CT studies with MET and FLT before surgery. The molecular features and histopathological diagnosis based on the 2016 WHO classification were determined using surgical specimens. The ratios of the maximum standardized uptake value (SUV) of the tumours to the mean SUV of the contralateral cortex (T/N ratios) were calculated on MET-PET/CT and FLT-PET/CT images.

Results

The mean T/N ratios of MET-PET/CT and FLT-PET/CT in IDH1-wildtype tumours were significantly higher than those in IDH1-mutant tumours (P < 0.001 and P < 0.001, respectively). Receiver operating characteristic analysis for differentiating IDH1 mutation status showed that the area under the curve of the FLT T/N ratio was significantly larger than that of the MET T/N ratio (P < 0.01). The mean T/N ratio of FLT-PET/CT in IDH1-wildtype tumours was significantly higher than that in IDH1-mutant tumours among grade II and III gliomas (P = 0.005), but this was not the case for MET-PET/CT. Both MET-PET/CT and FLT-PET/CT were able to distinguish between grade II and III gliomas in IDH1-mutant tumours (P = 0.002 and P < 0.001, respectively), but only FLT-PET/CT was able to distinguish between grade III and IV gliomas in IDH1-wildtype tumours (P = 0.029).

Conclusion

This study showed that FLT-PET/CT can be used to determine the IDH1 mutation status and evaluate glioma grade more accurately than MET-PET/CT. FLT-PET/CT can improve glioma differentiation based on the 2016 WHO classification, but caution must be paid for tumours without contrast enhancement and further studies should be conducted with more cases.

Increased 14C-acetate accumulation in IDH-mutated human glioblastoma: implications for detecting IDH-mutated glioblastoma with 11C-acetate PET imaging

PURPOSE

Recently, the potential value of isocitrate dehydrogenase (IDH) mutation as a prognostic marker in glioblastomas has been established. Glioblastomas are classified by their IDH mutation status under the 2016 WHO classification system. However, noninvasive diagnostic methods for the mutation status in glioblastoma patients have not been established so far. The purpose of this study was to evaluate the difference of acetate metabolism between in glioblastomas with wild-type IDH and in those with IDH mutation by comparing the uptake of ¹⁴C-acetate using genetically engineered glioblastoma cell lines in vitro and in vivo.

METHODS

We established glioblastoma cells (U251) expressing IDH1 R132H and examined the cell uptake of [1-¹⁴C]acetate. Biodistribution studies and an autoradiographic study for U251 cell tumor-bearing mice (BALB/c-nu/nu) with or without the IDH1 mutation were performed 1 h after [1-¹⁴C]acetate administration.

RESULTS

Significantly higher uptake of [1-¹⁴C]acetate was observed in U251/IDH1 R132H cells than in U251/IDH1 wild-type cells both in vitro (10.11 ± 0.94 vs. 4.26 ± 0.95%dose/mg, p = 0.0047) and in vivo (0.97 ± 0.14 vs. 0.66 ± 0.05%ID/g; p = 0.0037). Tumor-to-muscle ratios were also significantly higher in U251/IDH1 R132H tumors (3.36 ± 0.41 vs. 1.88 ± 0.59, p = 0.0030). The autoradiographic study shows the entirely higher radioactivity of the U251/IDH1 R132H tumor tissue section than that of the U251/IDH1 Wild-type tumor.

CONCLUSIONS

In vitro and in vivo studies demonstrated that the uptake of radiolabeled acetate was significantly higher in IDH-mutated cells than in IDH-wild-type cells.