The role of amino-acid PET in the light of the new WHO classification 2016 for brain tumors

Updates in IDH-Wildtype Glioblastoma

Glioblastoma is the most aggressive primary brain tumor with a poor prognosis. The 2021 WHO CNS5 classification has further stressed the importance of molecular signatures in diagnosis although therapeutic breakthroughs are still lacking. In this review article, updates on the current and novel therapies in IDH-wildtype GBM will be discussed.

Amino Acid PET Imaging with 18F-DOPA in the evaluation of Pediatric Brain Tumors

Although MRI is the workhorse of brain tumor initial evaluation and follow-up, there is a growing amount of data recommending the incorporation of amino-acid PET imaging at different stages of the management of these patients. Recent nuclear medicine and neuro-oncology clinical practice recommendations support the use of amino-acid imaging in brain tumor imaging. Considering 18F-DOPA is FDA approved for the evaluation of parkinsonian syndromes, it could be used clinically for other valuable clinical indications such as brain tumor evaluations. This value seems to be well established in adults and has growing evidence for its use in pediatrics as well. We offer to present four pediatric brain tumor cases imaged with 18F-DOPA and review the literature.

MGMT Promoter Methylation and IDH1 Mutations Do Not Affect [18F]FDOPA Uptake in Primary Brain Tumors

The aim of our study was to investigate the effects of methylation of O⁶-methylguanine-DNA methyltransferase promoter (MGMTp) and isocitrate dehydrogenase 1 (IDH 1) mutations on amino acid metabolism evaluated with 3,4-dihydroxy-6-[¹⁸F]-fluoro-l-phenylalanine ([¹⁸F] FDOPA) positron emission tomography/computed tomography (PET/CT). Seventy-two patients with primary brain tumors were enrolled in the study (33 women and 39 men; mean age 44 ± 12 years old). All of them were subjected to PET/CT examination after surgical treatment. Of them, 29 (40.3%) were affected by grade II glioma and 43 (59.7%) by grade III. PET/CT was scored as positive or negative and standardized uptake value ratio (SUVr) was calculated as the ratio between SUVmax of the lesion vs. that of the background. Statistical analysis was performed with the Mann–Whitney U test. Methylation of MGMTp was detectable in 61 out of the 72 patients examinated. Mean SUVr in patients without methylation of MGMTp was 1.44 ± 0.38 vs. 1.35 ± 0.48 of patients with methylation (p = 0.15). Data on IDH1 mutations were available for 43 subjects; of them, 31 are IDH-mutant. Mean SUVr was 1.38 ± 0.51 in patients IDH mutant and 1.46 ± 0.56 in patients IDH wild type. MGMTp methylation and IDH1 mutations do not affect [¹⁸F] FDOPA uptake in primary brain tumors and therefore cannot be assessed or predicted by radiopharmaceutical uptake parameters.

Glioblastoma in adults: a Society for Neuro-Oncology (SNO) and European Society of Neuro-Oncology (EANO) consensus review on current management and future directions

Glioblastomas are the most common form of malignant primary brain tumor and an important cause of morbidity and mortality. In recent years there have been important advances in understanding the molecular pathogenesis and biology of these tumors, but this has not translated into significantly improved outcomes for patients. In this consensus review from the Society for Neuro-Oncology (SNO) and the European Association of Neuro-Oncology (EANO), the current management of isocitrate dehydrogenase wildtype (IDHwt) glioblastomas will be discussed. In addition, novel therapies such as targeted molecular therapies, agents targeting DNA damage response and metabolism, immunotherapies, and viral therapies will be reviewed, as well as the current challenges and future directions for research.

Identification of a Specific Gene Module for Predicting Prognosis in Glioblastoma Patients

Introduction: Glioblastoma (GBM) is the most common and malignant variant of intrinsic glial brain tumors. The poor prognosis of GBM has not significantly improved despite the development of innovative diagnostic methods and new therapies. Therefore, further understanding the molecular mechanism that underlies the aggressive behavior of GBM and the identification of appropriate prognostic markers and therapeutic targets is necessary to allow early diagnosis, to develop appropriate therapies and to improve prognoses.

Methods: We used a weighted gene co-expression network analysis (WGCNA) to construct a gene co-expression network with 524 glioblastoma samples from The Cancer Genome Atlas (TCGA). A risk score was then constructed based on four module genes and the patients' overall survival (OS) rate. The prognostic and predictive accuracy of the risk score were verified in the GSE16011 cohort and the REMBRANDT cohort.

Results: We identified a gene module (the green module) related to prognosis. Then, multivariate Cox analysis was performed on 4 hub genes to construct a Cox proportional hazards regression model from 524 glioblastoma patients. A risk score for predicting survival time was calculated with the following formula based on the top four genes in the green module: risk score = (0.00889 × EXP_CLEC5A) + (0.0681 × EXP_FMOD) + (0.1724 × EXP_FKBP9) + (0.1557 × EXP_LGALS8). The 5-year survival rate of the high-risk group (survival rate: 2.7%, 95% CI: 1.2–6.3%) was significantly lower than that of the low-risk group (survival rate: 8.8%, 95% CI: 5.5–14.1%).

Conclusions: This study demonstrated the potential application of a WGCNA-based gene prognostic model for predicting the survival outcome of glioblastoma patients.

18F-DOPA uptake does not correlate with IDH mutation status and 1p/19q co-deletion in glioma

OBJECTIVE

The role of amino acid positron emission tomography (PET) in glioma grading and outcome prognostication has not yet been well established. This is particularly true in the context of the new WHO 2016 classification, which introduced a definition of glioma subtypes primarily based on molecular fingerprints. The aim of the present study was to correlate 3,4‑dihydroxy‑6‑[¹⁸F]‑fluoro-L‑phenylalanine (F-DOPA) uptake parameters with IDH mutation, 1p/19q status, and survival outcomes in patients with glioma.

METHODS

The study population consisted of 33 patients (17 M/16 F, mean age: 46 ± 13 years) who underwent F-DOPA PET/CT for the evaluation of tumor extent before the start of chemo or radiotherapy. The presence of IDH mutation and 1p/19q status was assessed in all the cases. Tumor volume and semiquantitative uptake parameters, namely SUV_max, tumor-to-normal brain ratio and tumor-to-normal striatum ratio, were calculated for each tumor. Imaging-derived parameters were compared between patients stratified according to molecular fingerprints, using parametric or non-parametric tests, where appropriate. The Kaplan-Meier method was used to assess differences of overall survival (OS) and progression-free survival (PFS) between groups. PET parameters were also tested as prognostic factors in univariate Cox survival regression models.

RESULTS

There were 12 IDH-wild-type and 21 IDH-mutant patients. Stratification according to 1p/19q co-deletion resulted in 20 non-co-deleted and 13 co-deleted patients. Median follow-up time from PET/CT exam was 30.5 months (range 3.5-74 months). Semiquantitative uptake parameters did correlate neither with IDH mutation nor with 1p/19q status. Uptake was similar in low-grade and high-grade tumors, respectively. In addition, F-DOPA uptake parameters, macroscopic tumor volume, or tumor grade did not stratify OS, while a correlation between SUV_max and PFS was shown in the subgroup of astrocytomas. On the other hand, IDH mutation status and presence of 1p/19q co-deletion had a significant impact on survival outcomes. The prognostic value of IDH mutation status was also confirmed in the subgroup of patients with astrocytic tumors.

CONCLUSIONS

F-DOPA uptake parameters do not correlate with tumor molecular and histological characteristics. The predictive value of PET-derived parameters on outcomes of survival is limited.