Prediction of response to lomustine-based chemotherapy in glioma patients at recurrence using MRI and FET PET

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

PURPOSE

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-[ 18 F]-fluoroethyl)-L-tyrosine (FET) PET information compared with FET PET results alone to differentiate tumor relapse from treatment-related changes.

PATIENTS AND METHODS

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).

RESULTS

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).

CONCLUSIONS

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.

Oligodendroglioma of the Hippocampus: A Case Report and Systematic Review on Therapeutic Approaches of Oligodendroglioma After WHO 2021 Classification

Background: Oligodendrogliomas are a molecularly distinct subtype of glioma according to the WHO 2021 tumor classification, defined as isocitrate dehydrogenase (IDH) mutations and 1p/19q co-deletion. This updated classification has changed the approach to glioma management by emphasizing the critical role of molecular diagnostics. This study explores current therapeutic strategies for adult oligodendrogliomas and contextualizes findings with a patient with a Grade 3 oligodendroglioma of the hippocampus. Methods: A systematic review was conducted, synthesizing evidence from 36 studies published between 2021 and 2024. The review focuses on surgical resection, PCV chemotherapy (procarbazine, lomustine, vincristine), and radiotherapy, with progression-free survival (PFS) and overall survival (OS) as primary outcomes. Moreover, a 45-year-old woman diagnosed with an IDH-mutant, 1p/19q-co-deleted Grade 3 oligodendroglioma is presented to illustrate clinical management. Results: The review highlights the significance of molecular profiling in personalizing treatment strategies. The findings highlight that maximal safe surgical resection combined with PCV chemotherapy and radiotherapy optimizes PFS and OS. However, our case underwent chemotherapy and radiotherapy after a multidisciplinary consultation, demonstrating favorable initial outcomes. These findings reaffirm the importance of integrating molecular insight into clinical decision-making. Conclusions: Advancements in molecular diagnostics have profoundly enhanced the personalization of therapy for oligodendrogliomas, yielding improved survival outcomes. Optimal management should entail a multidisciplinary approach incorporating surgery, chemotherapy, and radiotherapy, guided by molecular features. This study reinforces the necessity of molecular-driven strategies to improve survival and quality of care for patients with oligodendroglioma.

Towards Effective Treatment of Glioblastoma: The Role of Combination Therapies and the Potential of Phytotherapy and Micotherapy

Glioblastoma multiforme (GBM) is one of the most aggressive and difficult-to-treat brain tumors, with a poor prognosis due to its high resistance to conventional therapies. Current treatment options, including surgical resection, radiotherapy, and chemotherapy, have limited effectiveness in improving long-term survival. Despite the emergence of new therapies, monotherapy approaches have not shown significant improvements, highlighting the need for innovative therapeutic strategies. Combination therapies appear to be the most promising solution, as they target multiple molecular pathways involved in GBM progression. One area of growing interest is the incorporation of phytotherapy and micotherapy as complementary treatments, which offer potential benefits due to their anti-tumor, anti-inflammatory, and immunomodulatory properties. This review examines the current challenges in GBM treatment, discusses the potential of combination therapies, and highlights the promising role of phytotherapy and micotherapy as integrative therapeutic options for GBM management.

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.

Contribution of [18F]FET PET in the Management of Gliomas, from Diagnosis to Follow-Up: A Review

Gliomas, the most common type of primary malignant brain tumors in adults, pose significant challenges in diagnosis and management due to their heterogeneity and potential aggressiveness. This review evaluates the utility of O-(2-[18F]fluoroethyl)-L-tyrosine ([18F]FET) positron emission tomography (PET), a promising imaging modality, to enhance the clinical management of gliomas. We reviewed 82 studies involving 4657 patients, focusing on the application of [18F]FET in several key areas: diagnosis, grading, identification of IDH status and presence of oligodendroglial component, guided resection or biopsy, detection of residual tumor, guided radiotherapy, detection of malignant transformation in low-grade glioma, differentiation of recurrence versus treatment-related changes and prognostic factors, and treatment response evaluation. Our findings confirm that [18F]FET helps delineate tumor tissue, improves diagnostic accuracy, and aids in therapeutic decision-making by providing crucial insights into tumor metabolism. This review underscores the need for standardized parameters and further multicentric studies to solidify the role of [18F]FET PET in routine clinical practice. By offering a comprehensive overview of current research and practical implications, this paper highlights the added value of [18F]FET PET in improving management of glioma patients from diagnosis to follow-up.

PET-based response assessment criteria for diffuse gliomas (PET RANO 1.0): a report of the RANO group

Response Assessment in Neuro-Oncology (RANO) response criteria have been established and were updated in 2023 for MRI-based response evaluation of diffuse gliomas in clinical trials. In addition, PET-based imaging with amino acid tracers is increasingly considered for disease monitoring in both clinical practice and clinical trials. So far, a standardised framework defining timepoints for baseline and follow-up investigations and response evaluation criteria for PET imaging of diffuse gliomas has not been established. Therefore, in this Policy Review, we propose a set of criteria for response assessment based on amino acid PET imaging in clinical trials enrolling participants with diffuse gliomas as defined in the 2021 WHO classification of tumours of the central nervous system. These proposed PET RANO criteria provide a conceptual framework that facilitates the structured implementation of PET imaging into clinical research and, ultimately, clinical routine. To this end, the PET RANO 1.0 criteria are intended to encourage specific investigations of amino acid PET imaging of gliomas.

Magnetic resonance imaging and o-(2-[18F]fluoroethyl)-l-tyrosine positron emission tomography for early response assessment of nivolumab and bevacizumab in patients with recurrent high-grade astrocytic glioma

Background

In the present study, early response assessment by o-(2-[18F]fluoroethyl)-l-tyrosine (FET) positron emission tomography (PET) and contrast-enhanced magnetic resonance imaging (MRI) were investigated in a phase II open-label single-center study of nivolumab plus bevacizumab for recurrent high-grade astrocytic glioma.

Methods

Twenty patients with nonresectable first recurrence of high-grade astrocytic glioma after EORTC/NCIC protocol underwent [18F]FET PET/MRI at baseline and after 2 cycles of treatment. Whole brain values of contrast-enhancing volume on MRI (CEV), of the mean (TBRmean) and maximal tumor-to-background ratio (TBRmax), and of metabolically active volume (MTV) on [18F]FET PET were obtained. Regional changes in [18F]FET uptake were assessed by parametric response mapping (PRM). Prediction of overall survival (OS) and response (OS > 11 months) were assessed by Cox and receiver operating characteristic (ROC) analysis, respectively. Also, MRI (response assessment in neuro-oncology [RANO] 2.0) and PET-based (PET RANO 1.0) response assessment criteria were compared.

Results

In ROC analysis responders were separated (P < .05) from nonresponders by lower MTV at follow-up (AUC 0.771, cutoff 18.3 mL), larger decrease in MTV (AUC 0.757, cutoff -5.3 mL), larger decrease in both TBRmax (AUC 0.814, cutoff -0.53) and relative TBRmax (AUC 0.829, cutoff -11%) and smaller PRM progressive volume (AUC 0.843, cutoff 4.0 mL). Change in CEV did not predict response. RANO 2.0 and PET RANO response assessment criteria had similar and only borderline prognostic values.

Conclusions

The study indicates that [18F]FET PET is superior to contrast-enhanced MRI for early response assessment in patients with recurrent high-grade astrocytic glioma treated with nivolumab and bevacizumab.

18F-Fluoroethyl-L Tyrosine Positron Emission Tomography Radiomics in the Differentiation of Treatment-Related Changes from Disease Progression in Patients with Glioblastoma

The follow-up of glioma patients after therapeutic intervention remains a challenging topic, as therapy-related changes can emulate true progression in contrast-enhanced magnetic resonance imaging. 18F-fluoroethyl-tyrosine (18F-FET) is a radiopharmaceutical that accumulates in glioma cells due to an increased expression of L-amino acid transporters and, contrary to gadolinium, does not depend on blood-brain barrier disruption to reach tumoral cells. It has demonstrated a high diagnostic value in the differentiation of tumoral viability and pseudoprogression or any other therapy-related changes, especially when combining traditional visual analysis with modern radiomics. In this review, we aim to cover the potential role of 18F-FET positron emission tomography in everyday clinical practice when applied to the follow-up of patients after the first therapeutical intervention, early response evaluation, and the differential diagnosis between therapy-related changes and progression.

Clinical Value of Hybrid PET/MR Imaging: Brain Imaging Using PET/MR Imaging

Hybrid PET/MR imaging offers a unique opportunity to acquire MR imaging and PET information during a single imaging session. PET/MR imaging has numerous advantages, including enhanced diagnostic accuracy, improved disease characterization, and better treatment planning and monitoring. It enables the immediate integration of anatomic, functional, and metabolic imaging information, allowing for personalized characterization and monitoring of neurologic diseases. This review presents recent advances in PET/MR imaging and highlights advantages in clinical practice for neuro-oncology, epilepsy, and neurodegenerative disorders. PET/MR imaging provides valuable information about brain tumor metabolism, perfusion, and anatomic features, aiding in accurate delineation, treatment response assessment, and prognostication.

Automated Brain Tumor Detection and Segmentation for Treatment Response Assessment Using Amino Acid PET

Evaluation of metabolic tumor volume (MTV) changes using amino acid PET has become an important tool for response assessment in brain tumor patients. MTV is usually determined by manual or semiautomatic delineation, which is laborious and may be prone to intra- and interobserver variability. The goal of our study was to develop a method for automated MTV segmentation and to evaluate its performance for response assessment in patients with gliomas. Methods: In total, 699 amino acid PET scans using the tracer O-(2-[18F]fluoroethyl)-l-tyrosine (18F-FET) from 555 brain tumor patients at initial diagnosis or during follow-up were retrospectively evaluated (mainly glioma patients, 76%). 18F-FET PET MTVs were segmented semiautomatically by experienced readers. An artificial neural network (no new U-Net) was configured on 476 scans from 399 patients, and the network performance was evaluated on a test dataset including 223 scans from 156 patients. Surface and volumetric Dice similarity coefficients (DSCs) were used to evaluate segmentation quality. Finally, the network was applied to a recently published 18F-FET PET study on response assessment in glioblastoma patients treated with adjuvant temozolomide chemotherapy for a fully automated response assessment in comparison to an experienced physician. Results: In the test dataset, 92% of lesions with increased uptake (n = 189) and 85% of lesions with iso- or hypometabolic uptake (n = 33) were correctly identified (F1 score, 92%). Single lesions with a contiguous uptake had the highest DSC, followed by lesions with heterogeneous, noncontiguous uptake and multifocal lesions (surface DSC: 0.96, 0.93, and 0.81 respectively; volume DSC: 0.83, 0.77, and 0.67, respectively). Change in MTV, as detected by the automated segmentation, was a significant determinant of disease-free and overall survival, in agreement with the physician's assessment. Conclusion: Our deep learning-based 18F-FET PET segmentation allows reliable, robust, and fully automated evaluation of MTV in brain tumor patients and demonstrates clinical value for automated response assessment.

Amino Acid PET in Neurooncology

For decades, several amino acid PET tracers have been used to optimize diagnostics in patients with brain tumors. In clinical routine, the most important clinical indications for amino acid PET in brain tumor patients are differentiation of neoplasm from nonneoplastic etiologies, delineation of tumor extent for further diagnostic and treatment planning (i.e., diagnostic biopsy, resection, or radiotherapy), differentiation of treatment-related changes such as pseudoprogression or radiation necrosis after radiation or chemoradiation from tumor progression at follow-up, and assessment of response to anticancer therapy, including prediction of patient outcome. This continuing education article addresses the diagnostic value of amino acid PET for patients with either glioblastoma or metastatic brain cancer.