Prediction of pathology and survival by FDG PET in gliomas

Advances in Neuro-Oncological Imaging: An Update on Diagnostic Approach to Brain Tumors

This study delineates the pivotal role of imaging within the field of neurology, emphasizing its significance in the diagnosis, prognostication, and evaluation of treatment responses for central nervous system (CNS) tumors. A comprehensive understanding of both the capabilities and limitations inherent in emerging imaging technologies is imperative for delivering a heightened level of personalized care to individuals with neuro-oncological conditions. Ongoing research in neuro-oncological imaging endeavors to rectify some limitations of radiological modalities, aiming to augment accuracy and efficacy in the management of brain tumors. This review is dedicated to the comparison and critical examination of the latest advancements in diverse imaging modalities employed in neuro-oncology. The objective is to investigate their respective impacts on diagnosis, cancer staging, prognosis, and post-treatment monitoring. By providing a comprehensive analysis of these modalities, this review aims to contribute to the collective knowledge in the field, fostering an informed approach to neuro-oncological care. In conclusion, the outlook for neuro-oncological imaging appears promising, and sustained exploration in this domain is anticipated to yield further breakthroughs, ultimately enhancing outcomes for individuals grappling with CNS tumors.

Combined Metabolic and Functional Tumor Volumes on [18F]FDG-PET/MRI in Neuroblastoma Using Voxel-Wise Analysis

PURPOSE

The purpose of our study was to evaluate the association between the [18F]FDG standard uptake value (SUV) and the apparent diffusion coefficient (ADC) in neuroblastoma (NB) by voxel-wise analysis.

METHODS

From our prospective observational PET/MRI study, a subcohort of patients diagnosed with NB with both baseline imaging and post-chemotherapy imaging was further investigated. After registration and tumor segmentation, metabolic and functional tumor volumes were calculated from the ADC and SUV values using dedicated software allowing for voxel-wise analysis. Under the mean of thresholds, each voxel was assigned to one of three virtual tissue groups: highly vital (v) (low ADC and high SUV), possibly low vital (lv) (high ADC and low SUV), and equivocal (e) with high ADC and high SUV or low ADC and low SUV. Moreover, three clusters were generated from the total tumor volumes using the method of multiple Gaussian distributions. The Pearson's correlation coefficient between the ADC and the SUV was calculated for each group.

RESULTS

Out of 43 PET/MRIs in 21 patients with NB, 16 MRIs in 8 patients met the inclusion criteria (PET/MRIs before and after chemotherapy). The proportion of tumor volumes were 26%, 36%, and 38% (v, lv, e) at baseline, 0.03%, 66%, and 34% after treatment in patients with response, and 42%, 25%, and 33% with progressive disease, respectively. In all clusters, the ADC and the SUV correlated negatively. In the cluster that corresponded to highly vital tissue, the ADC and the SUV showed a moderate negative correlation before treatment (R = -0.18; p < 0.0001) and the strongest negative correlation after treatment (R = -0.45; p < 0.0001). Interestingly, only patients with progression (n = 2) under therapy had a relevant part in this cluster post-treatment.

CONCLUSION

Our results indicate that voxel-wise analysis of the ADC and the SUV is feasible and can quantify the different quality of tissue in neuroblastic tumors. Monitoring ADCs as well as SUV levels can quantify tumor dynamics during therapy.

Imaging Cancer in Neuroradiology

Neuroimaging plays a pivotal role in the diagnosis, management, and prognostication of brain tumors. Recently, the World Health Organization published the fifth edition of the WHO Classification of Tumors of the Central Nervous System (CNS5), which places greater emphasis on tumor genetics and molecular markers to complement the existing histological and immunohistochemical approaches. Recent advances in computational power allowed modern neuro-oncological imaging to move from a strictly morphology-based discipline to advanced neuroimaging techniques with quantifiable tissue characteristics such as tumor cellularity, microstructural organization, hemodynamic, functional, and metabolic features, providing more precise tumor diagnosis and management. The aim of this review is to highlight the key imaging features of the recently published CNS5, outlining the current imaging standards and summarizing the latest advances in neuro-oncological imaging techniques and their role in complementing traditional brain tumor imaging and management.

Nuclear medicine and radiotherapy in the clinical management of glioblastoma patients

Introduction

The aim of the narrative review was to analyse the applications of nuclear medicine (NM) techniques such as PET/CT with different tracers in combination with radiotherapy for the clinical management of glioblastoma patients.

Materials and methods

Key references were derived from a PubMed query. Hand searching and clinicaltrials.gov were also used.

Results

This paper contains a narrative report and a critical discussion of NM approaches in combination with radiotherapy in glioma patients.

Conclusions

NM can provide the Radiation Oncologist several aids that can be useful in the clinical management of glioblastoma patients. At the same, these results need to be validated in prospective and multicenter trials.

PET/MRI in Pediatric Neuroimaging: Primer for Clinical Practice

Modern pediatric imaging seeks to provide not only exceptional anatomic detail but also physiologic and metabolic information of the pathology in question with as little radiation penalty as possible. Hybrid PET/MR imaging combines exquisite soft-tissue information obtained by MR imaging with functional information provided by PET, including metabolic markers, receptor binding, perfusion, and neurotransmitter release data. In pediatric neuro-oncology, PET/MR imaging is, in many ways, ideal for follow-up compared with PET/CT, given the superiority of MR imaging in neuroimaging compared with CT and the lower radiation dose, which is relevant in serial imaging and long-term follow-up of pediatric patients. In addition, although MR imaging is the main imaging technique for the evaluation of spinal pathology, PET/MR imaging may provide useful information in several clinical scenarios, including tumor staging and follow-up, treatment response assessment of spinal malignancies, and vertebral osteomyelitis. This review article covers neuropediatric applications of PET/MR imaging in addition to considerations regarding radiopharmaceuticals, imaging protocols, and current challenges to clinical implementation.

Advanced Imaging Techniques for Newly Diagnosed and Recurrent Gliomas

Management of gliomas following initial diagnosis requires thoughtful presurgical planning followed by regular imaging to monitor treatment response and survey for new tumor growth. Traditional MR imaging modalities such as T1 post-contrast and T2-weighted sequences have long been a staple of tumor diagnosis, surgical planning, and post-treatment surveillance. While these sequences remain integral in the management of gliomas, advances in imaging techniques have allowed for a more detailed characterization of tumor characteristics. Advanced MR sequences such as perfusion, diffusion, and susceptibility weighted imaging, as well as PET scans have emerged as valuable tools to inform clinical decision making and provide a non-invasive way to help distinguish between tumor recurrence and pseudoprogression. Furthermore, these advances in imaging have extended to the operating room and assist in making surgical resections safer. Nevertheless, surgery, chemotherapy, and radiation treatment continue to make the interpretation of MR changes difficult for glioma patients. As analytics and machine learning techniques improve, radiomics offers the potential to be more quantitative and personalized in the interpretation of imaging data for gliomas. In this review, we describe the role of these newer imaging modalities during the different stages of management for patients with gliomas, focusing on the pre-operative, post-operative, and surveillance periods. Finally, we discuss radiomics as a means of promoting personalized patient care in the future.

Feasibility on the Use of Radiomics Features of 11[C]-MET PET/CT in Central Nervous System Tumours: Preliminary Results on Potential Grading Discrimination Using a Machine Learning Model

Background/Aim: Nowadays, Machine Learning (ML) algorithms have demonstrated remarkable progress in image-recognition tasks and could be useful for the new concept of precision medicine in order to help physicians in the choice of therapeutic strategies for brain tumours. Previous data suggest that, in the central nervous system (CNS) tumours, amino acid PET may more accurately demarcate the active disease than paramagnetic enhanced MRI, which is currently the standard method of evaluation in brain tumours and helps in the assessment of disease grading, as a fundamental basis for proper clinical patient management. The aim of this study is to evaluate the feasibility of ML on 11[C]-MET PET/CT scan images and to propose a radiomics workflow using a machine-learning method to create a predictive model capable of discriminating between low-grade and high-grade CNS tumours. Materials and Methods: In this retrospective study, fifty-six patients affected by a primary brain tumour who underwent 11[C]-MET PET/CT were selected from January 2016 to December 2019. Pathological examination was available in all patients to confirm the diagnosis and grading of disease. PET/CT acquisition was performed after 10 min from the administration of 11C-Methionine (401–610 MBq) for a time acquisition of 15 min. 11[C]-MET PET/CT images were acquired using two scanners (24 patients on a Siemens scan and 32 patients on a GE scan). Then, LIFEx software was used to delineate brain tumours using two different semi-automatic and user-independent segmentation approaches and to extract 44 radiomics features for each segmentation. A novel mixed descriptive-inferential sequential approach was used to identify a subset of relevant features that correlate with the grading of disease confirmed by pathological examination and clinical outcome. Finally, a machine learning model based on discriminant analysis was used in the evaluation of grading prediction (low grade CNS vs. high-grade CNS) of 11[C]-MET PET/CT. Results: The proposed machine learning model based on (i) two semi-automatic and user-independent segmentation processes, (ii) an innovative feature selection and reduction process, and (iii) the discriminant analysis, showed good performance in the prediction of tumour grade when the volumetric segmentation was used for feature extraction. In this case, the proposed model obtained an accuracy of ~85% (AUC ~79%) in the subgroup of patients who underwent Siemens tomography scans, of 80.51% (AUC 65.73%) in patients who underwent GE tomography scans, and of 70.31% (AUC 64.13%) in the whole patients’ dataset (Siemens and GE scans). Conclusions: This preliminary study on the use of an ML model demonstrated to be feasible and able to select radiomics features of 11[C]-MET PET with potential value in prediction of grading of disease. Further studies are needed to improve radiomics algorithms to personalize predictive and prognostic models and potentially support the medical decision process.

Discordant findings of different positron emission tomography/CT tracers in a case of glioblastoma

¹⁸F-2-fluoro-2-deoxy-D-glucose ([¹⁸F]-FDG) positron emission tomography (PET) CT has proven useful in the evaluation of high-grade glioma and is also useful as a predictor of the degree of malignancy in newly diagnosed brain tumors. It is commonly accepted that high-grade gliomas are characterized by increased FDG uptake, whereas the low-grade glioma demonstrates reduced or absent FDG uptake. [¹⁸F]-FDOPA is an amino acid PET tracer which is a marker of the proliferative activity of brain tumors and demonstrates positive uptake in all grades of brain tumors; however, the degree of tracer uptake is significantly higher in high-grade tumors as compared to low-grade tumors. Here, we discuss a case where both FDG and DOPA PET/CT scans raised suspicion of low-grade glioma; however, the final histopathology report confirmed WHO grade IV Glioblastoma.

Short-term fasting in glioma patients: analysis of diet diaries and metabolic parameters of the ERGO2 trial

Purpose

The prospective, randomized ERGO2 trial investigated the effect of calorie-restricted ketogenic diet and intermittent fasting (KD-IF) on re-irradiation for recurrent brain tumors. The study did not meet its primary endpoint of improved progression-free survival in comparison to standard diet (SD). We here report the results of the quality of life/neurocognition and a detailed analysis of the diet diaries.

Methods

50 patients were randomized 1:1 to re-irradiation combined with either SD or KD-IF. The KD-IF schedule included 3 days of ketogenic diet (KD: 21–23 kcal/kg/d, carbohydrate intake limited to 50 g/d), followed by 3 days of fasting and again 3 days of KD. Follow-up included examination of cognition, quality of life and serum samples.

Results

The 20 patients who completed KD-IF met the prespecified goals for calorie and carbohydrate restriction. Substantial decreases in leptin and insulin and an increase in uric acid were observed. The SD group, of note, had a lower calorie intake than expected (21 kcal/kg/d instead of 30 kcal/kg/d). Neither quality of life nor cognition were affected by the diet. Low glucose emerged as a significant prognostic parameter in a best responder analysis.

Conclusion

The strict caloric goals of the ERGO2 trial were tolerated well by patients with recurrent brain cancer. The short diet schedule led to significant metabolic changes with low glucose emerging as a candidate marker of better prognosis. The unexpected lower calorie intake of the control group complicates the interpretation of the results.

Clinicaltrials.gov number: NCT01754350; Registration: 21.12.2012.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02666-1.

miR-542-3p Contributes to the HK2-Mediated High Glycolytic Phenotype in Human Glioma Cells

(1) Background: The elevation of glucose metabolism is linked to high-grade gliomas such as glioblastoma multiforme (GBM). The high glycolytic phenotype is associated with cellular proliferation and resistance to treatment with chemotherapeutic agents in GBM. MicroRNA-542-3p (miR-542-3p) has been implicated in several tumors including gliomas. However, the role of miR-542-3p in glucose metabolism in human gliomas remains unclear; (2) Methods: We measured the levels of cellular proliferation in human glioma cells. We measured the glycolytic activity in miR-542-3p knockdown and over-expressed human glioma cells. We measured the levels of miR-542-3p and HK2 in glioma tissues from patients with low- and high-grade gliomas using imaging analysis; (3) Results: We show that knockdown of miR-542-3p significantly suppressed cellular proliferation in human glioma cells. Knockdown of miR-542-3p suppressed HK2-induced glycolytic activity in human glioma cells. Consistently, over-expression of miR-542-3p increased HK2-induced glycolytic activity in human glioma cells. The levels of miR-542-3p and HK2 were significantly elevated in glioma tissues of patients with high-grade gliomas relative to that in low-grade gliomas. The elevation of HK2 levels in patients with high-grade gliomas were positively correlated with the high levels of miR-542-3p in GBM and low-grade gliomas (LGG) based on the datasets from the Cancer Genome Atlas (TCGA) database. Moreover, the high levels of miR-542-3p were associated with poor survival rate in the TCGA database; (4) Conclusions: miR-542-3p contributes to the HK2-mediated high glycolytic phenotype in human glioma cells.

Exploring the crosstalk of glycolysis and mitochondrial metabolism in psychiatric disorders and brain tumours

Dysfunction of metabolic pathways characterises a plethora of common pathologies and has emerged as an underlying hallmark of disease phenotypes. Here, we focus on psychiatric disorders and brain tumours and explore changes in the interplay between glycolysis and mitochondrial energy metabolism in the brain. We discuss alterations in glycolysis versus core mitochondrial metabolic pathways, such as the tricarboxylic acid cycle and oxidative phosphorylation, in major psychiatric disorders and brain tumours. We investigate potential common patterns of altered mitochondrial metabolism in different brain regions and sample types and explore how changes in mitochondrial number, shape and morphology affect disease-related manifestations. We also highlight the potential of pharmacologically targeting mitochondria to achieve therapeutic effects.

A Critical Review of PET Tracers Used for Brain Tumor Imaging

The brain is a common site for metastases as well as primary tumors. Although evaluation of these malignancies with contrast-enhanced MR imaging defines current clinical practice, ¹⁸F-fluorodeoxyglucose (FDG)-PET has shown considerable utility in this area. In addition, many other tracers targeting various aspects of tumor biology have been developed and tested. This article discusses recent developments in PET imaging and the anticipated role of FDG and other tracers in the assessment of brain tumors.

Pseudoprogression versus true progression in glioblastoma patients: A multiapproach literature review. Part 2 - Radiological features and metric markers

After chemoradiotherapy for glioblastoma, pseudoprogression can occur and must be distinguished from true progression to correctly manage glioblastoma treatment and follow-up. Conventional treatment response assessment is evaluated via conventional MRI (contrast-enhanced T1-weighted and T2/FLAIR), which is unreliable. The emergence of advanced MRI techniques, MR spectroscopy, and PET tracers has improved pseudoprogression diagnostic accuracy. This review presents a literature review of the different imaging techniques and potential imaging biomarkers to differentiate pseudoprogression from true progression.

PET and SPECT Imaging of the Brain: History, Technical Considerations, Applications, and Radiotracers

Advances in nuclear medicine have revolutionized our ability to accurately diagnose patients with a wide array of neurologic pathologies and provide appropriate therapy. The development of new radiopharmaceuticals has made possible the identification of regional differences in brain tissue composition and metabolism. In addition, the evolution of 3-dimensional molecular imaging followed by fusion with computed tomography and magnetic resonance imaging have allowed for more precise localization of pathologies. This review will introduce single photon emission computed tomography and positron emission tomographic imaging of the brain, including the history of their development, technical considerations, and a brief overview of pertinent radiopharmaceuticals and their applications.

Sex differences in health and disease: A review of biological sex differences relevant to cancer with a spotlight on glioma

The influence of biological sex differences on human health and disease, while being increasingly recognized, has long been underappreciated and underexplored. While humans of all sexes are more alike than different, there is evidence for sex differences in the most basic aspects of human biology and these differences have consequences for the etiology and pathophysiology of many diseases. In a disease like cancer, these consequences manifest in the sex biases in incidence and outcome of many cancer types. The ability to deliver precise, targeted therapies to complex cancer cases is limited by our current understanding of the underlying sex differences. Gaining a better understanding of the implications and interplay of sex differences in diseases like cancer will thus be informative for clinical practice and biological research. Here we review the evidence for a broad array of biological sex differences in humans and discuss how these differences may relate to observed sex differences in various diseases, including many cancers and specifically glioblastoma. We focus on areas of human biology that play vital roles in healthy and disease states, including metabolism, development, hormones, and the immune system, and emphasize that the intersection of sex differences in these areas should not go overlooked. We further propose that mathematical approaches can be useful for exploring the extent to which sex differences affect disease outcomes and accounting for those in the development of therapeutic strategies.

Exploiting Cancer's Tactics to Make Cancer a Manageable Chronic Disease

The history of modern oncology started around eighty years ago with the introduction of cytotoxic agents such as nitrogen mustard into the clinic, followed by multi-agent chemotherapy protocols. Early success in radiation therapy in Hodgkin lymphoma gave birth to the introduction of radiation therapy into different cancer treatment protocols. Along with better understanding of cancer biology, we developed drugs targeting cancer-related cellular and genetic aberrancies. Discovery of the crucial role of vasculature in maintenance, survival, and growth of a tumor opened the way to the development of anti-angiogenic agents. A better understanding of T-cell regulatory pathways advanced immunotherapy. Awareness of stem-like cancer cells and their role in cancer metastasis and local recurrence led to the development of drugs targeting them. At the same time, sequential and rapidly accelerating advances in imaging and surgical technology have markedly increased our ability to safely remove ≥90% of tumor cells. While we have advanced our ability to kill cells from multiple directions, we have still failed to stop most types of cancer from recurring. Here we analyze the tactics employed in cancer evolution; namely, chromosomal instability (CIN), intra-tumoral heterogeneity (ITH), and cancer-specific metabolism. These tactics govern the resistance to current cancer therapeutics. It is time to focus on maximally delaying the time to recurrence, with drugs that target these fundamental tactics of cancer evolution. Understanding the control of CIN and the optimal state of ITH as the most important tactics in cancer evolution could facilitate the development of improved cancer therapeutic strategies designed to transform cancer into a manageable chronic disease.

Clinical Imaging for Diagnostic Challenges in the Management of Gliomas: A Review

Neuroimaging plays a critical role in the management of patients with gliomas. While conventional magnetic resonance imaging (MRI) remains the standard imaging modality, it is frequently insufficient to inform clinical decision-making. There is a need for noninvasive strategies for reliably distinguishing low-grade from high-grade gliomas, identifying important molecular features of glioma, choosing an appropriate target for biopsy, delineating target area for surgery or radiosurgery, and distinguishing tumor progression (TP) from pseudoprogression (PsP). One recent advance is the identification of the T2/fluid-attenuated inversion recovery mismatch sign on standard MRI to identify isocitrate dehydrogenase mutant astrocytomas. However, to meet other challenges, neuro-oncologists are increasingly turning to advanced imaging modalities. Diffusion-weighted imaging modalities including diffusion tensor imaging and diffusion kurtosis imaging can be helpful in delineating tumor margins and better visualization of tissue architecture. Perfusion imaging including dynamic contrast-enhanced MRI using gadolinium or ferumoxytol contrast agents can be helpful for grading as well as distinguishing TP from PsP. Positron emission tomography is useful for measuring tumor metabolism, which correlates with grade and can distinguish TP/PsP in the right setting. Magnetic resonance spectroscopy can identify tissue by its chemical composition, can distinguish TP/PsP, and can identify molecular features like 2-hydroxyglutarate. Finally, amide proton transfer imaging measures intracellular protein content, which can be used to identify tumor grade/progression and distinguish TP/PsP.

Contribution of Different Positron Emission Tomography Tracers in Glioma Management: Focus on Glioblastoma

Although rare, glioblastomas account for the majority of primary brain lesions, with a dreadful prognosis. Magnetic resonance imaging (MRI) is currently the imaging method providing the higher resolution. However, it does not always succeed in distinguishing recurrences from non-specific temozolomide, have been shown to improve -related changes caused by the combination of radiotherapy, chemotherapy, and targeted therapy, also called pseudoprogression. Strenuous attempts to overcome this issue is highly required for these patients with a short life expectancy for both ethical and economic reasons. Additional reliable information may be obtained from positron emission tomography (PET) imaging. The development of this technique, along with the emerging of new classes of tracers, can help in the diagnosis, prognosis, and assessment of therapies. We reviewed the current data about the commonly used tracers, such as 18F-fluorodeoxyglucose (18F-FDG) and radiolabeled amino acids, as well as different PET tracers recently investigated, to report their strengths, limitations, and relevance in glioblastoma management.

New metabolic imaging tools in neuro-oncology

PURPOSE OF REVIEW

The current treatment of gliomas dovetails results of decades-old clinical trials with modern trends in chemotherapy. Molecular characterization now plays a pivotal role, and IDH mutations are key characteristics and the subject of active debate. IDH-mutant tumors produce the 'onco-metabolite', 2-hydroxyglutarate. Metabolic changes have become central to the understanding of tumor biology, and tumors display a fundamental metabolic change called the Warburg Effect. The Warburg Effect represents a preference for glycolysis, as opposed to oxidative phosphorylation. The present review details the clinical context and discusses clinical and preclinical metabolic imaging tools to characterize the Warburg Effect.

RECENT FINDINGS

A clinical Warburg Index is proposed, defined as the lactate concentration measured by H-MRSI over the SUV measured by FDG-PET, to measure the Warburg Effect. A preclinical technique called deuterium metabolic imaging has successfully imaged the Warburg Effect in vivo in glioblastoma.

SUMMARY

Metabolic imaging provides an opportunity to measure the Warburg Effect and other metabolic changes in brain tumors. An increased understanding of metabolic shifts integral to brain cancer has the potential to address multiple contemporary debates on glioma pathophysiology and treatment. Metabolic imaging tools thus have the potential to advance research findings, clinical trial development, and clinical care.

What Does Reduced FDG Uptake Mean in High-Grade Gliomas?

PURPOSE

As well as in many others cancers, FDG uptake is correlated with the degree of malignancy in gliomas, that is, commonly high FDG uptake in high-grade gliomas. However, in clinical practice, it is not uncommon to observe high-grade gliomas with low FDG uptake. Our aim was to explore the tumor metabolism in 2 populations of high-grade gliomas presenting high or low FDG uptake.

METHODS

High-resolution magic-angle spinning nuclear magnetic resonance spectroscopy was realized on tissue samples from 7 high-grade glioma patients with high FDG uptake and 5 high-grade glioma patients with low FDG uptake. Tumor metabolomics was evaluated from 42 quantified metabolites and compared by network analysis.

RESULTS

Whether originating from astrocytes or oligodendrocytes, the high-grade gliomas with low FDG avidity represent a subgroup of high-grade gliomas presenting common characteristics: low aspartate, glutamate, and creatine levels, which are probably related to the impaired electron transport chain in mitochondria; high serine/glycine metabolism and so one-carbon metabolism; low glycerophosphocholine-phosphocholine ratio in membrane metabolism, which is associated with tumor aggressiveness; and finally negative MGMT methylation status.

CONCLUSIONS

It seems imperative to identify this subgroup of high-grade gliomas with low FDG avidity, which is especially aggressive. Their identification could be important for early detection for a possible personalized treatment, such as antifolate treatment.

Imaging-guided precision medicine in glioblastoma patients treated with immune checkpoint modulators: research trend and future directions in the field of imaging biomarkers and artificial intelligence

Immunotherapies that employ immune checkpoint modulators (ICMs) have emerged as an effective treatment for a variety of solid cancers, as well as a paradigm shift in the treatment of cancers. Despite this breakthrough, the median survival time of glioblastoma patients has remained at about 2 years. Therefore, the safety and anti-cancer efficacy of combination therapies that include ICMs are being actively investigated. Because of the distinct mechanisms of ICMs, which restore the immune system’s anti-tumor capacity, unconventional immune-related phenomena are increasingly being reported in terms of tumor response and progression, as well as adverse events. Indeed, immunotherapy response assessments for neuro-oncology (iRANO) play a central role in guiding cancer patient management and define a “wait and see strategy” for patients treated with ICMs in monotherapy with progressive disease on MRI. This article deciphers emerging research trends to ameliorate four challenges unaddressed by the iRANO criteria: (1) patient selection, (2) identification of immune-related phenomena other than pseudoprogression (i.e., hyperprogression, the abscopal effect, immune-related adverse events), (3) response assessment in combination therapies including ICM, and (4) alternatives to MRI. To this end, our article provides a structured approach for standardized selection and reporting of imaging modalities to enable the use of precision medicine by deciphering the characteristics of the tumor and its immune environment. Emerging preclinical or clinical innovations are also discussed as future directions such as immune-specific targeting and implementation of artificial intelligence algorithms.

Neuroimaging for Radiation Therapy of Brain Tumors

Delineating the gross tumor volume (GTV) is a core task within radiation treatment planning. GTVs must be precisely defined irrespective of the region involved, but even more so in a sensitive area such as the brain. As precision medicine cannot exist without precision imaging, the current article aims to discuss the various imaging modalities employed in the radiation treatment planning of brain tumors.Gliomas, meningiomas, and paragangliomas are some of the most challenging tumors and the advancement in diagnostic imaging can significantly contribute to their delineation. For gliomas, irradiation based on multiparametric magnetic resonance imaging (MRI) and amino-acid positron emission tomography (PET)/computed tomography (CT) may have a higher sensitivity and specificity, which could lead to a better sparing of organs at risk and help distinguish between tumor, edema, and radiogenic alterations. Meningiomas and paragangliomas are often associated with a good prognosis. Therefore, GTV delineation according to MRI and somatostatin receptor ligand-PET/CT plays an essential role in sparing sensitive structures and maintaining a good quality of life for these patients.The combination of multiparametric MRI and PET/CT (possibly in the form of PET/MRI) presently appears to be the optimal approach for target volume delineation. The comparative efficacy of these imaging modalities has to be further evaluated in prospective trials.

Comparison of dual-time point 18F-FDG PET/CT tumor-to-background ratio, intraoperative 5-aminolevulinic acid fluorescence scale, and Ki-67 index in high-grade glioma

The aim of this study was to compare preoperative dual-time point F-fluorodeoxyglucose (FDG) uptake pattern with intraoperative 5-aminolevulinic acid (5-ALA) fluorescence in high-grade gliomas. In addition, we assessed for possible associations with a pathologic parameter (Ki-67 index).Thirty-one patients with high-grade glioma (M:F = 19:12, mean age = 60.6 ± 11.2 years) who underwent dual-time point F-FDG positron emission tomography (PET)/computed tomography (CT) scan before surgery were retrospectively enrolled; 5-ALA was applied to the surgical field of all these patients and its fluorescence intensity was evaluated during surgery. Measured F-FDG PET/CT parameters were maximum and peak tumor-to-background ratio (maxTBR and peakTBR) at base (-base) and delayed (-delay) scan. The intensity of 5-ALA fluorescence was graded on a scale of three (grade I as no or mild intensity, grade II as moderate intensity, and grade III as strong intensity).Seven of the patients had WHO grade III brain tumors and 24 had WHO grade IV tumors (mean tumor size = 4.8 ± 1.8 cm). MaxTBR-delay and peakTBR-delay showed significantly higher values than maxTBR-base and peakTBR-base, respectively (all P < .001). Among the F-FDG PET/CT parameters, only maxTBR-delay demonstrated significance according to grade of 5-ALA (P = .030), and maxTBR-delay gradually decreased as the fluorescence intensity increased. Also, maxTBR-delay and peakTBR-delay showed significant positive correlation with Ki-67 index (P = .011 and .009, respectively).Delayed F-FDG uptake on PET/CT images could reflect proliferation in high-grade glioma, and it has a complementary role with 5-ALA fluorescence.

Applying Amide Proton Transfer MR Imaging to Hybrid Brain PET/MR: Concordance with Gadolinium Enhancement and Added Value to [18F]FDG PET

PURPOSE

The purpose of this study is to evaluate the diagnostic concordance and metric correlations of amide proton transfer (APT) imaging with gadolinium-enhanced magnetic resonance imaging (MRI) and 2-deoxy-2-[¹⁸F-]fluoro-D-glucose ([¹⁸F]FDG) positron emission tomography (PET), using hybrid brain PET/MRI.

PROCEDURES

Twenty-one subjects underwent brain gadolinium-enhanced [¹⁸F]FDG PET/MRI prospectively. Imaging accuracy was compared between unenhanced MRI, MRI with enhancement, APT-weighted (APTW) images, and PET based on six diagnostic criteria. Among tumors, the McNemar test was further used for concordance assessment between gadolinium-enhanced imaging, APT imaging, and [¹⁸F]FDG PET. As well, the relation of metrics between APT imaging and PET was analyzed by the Pearson correlation analysis.

RESULTS

APT imaging and gadolinium-enhanced MRI showed superior and similar diagnostic accuracy. APTW signal intensity and gadolinium enhancement were concordant in 19 tumors (100 %), while high [¹⁸F]FDG avidity was shown in only 12 (63.2 %). For the metrics from APT imaging and PET, there was significant correlation for 13 hypermetabolic tumors (P < 0.05) and no correlation for the remaining six [¹⁸F]FDG-avid tumors.

CONCLUSIONS

APT imaging can be used to increase diagnostic accuracy with no need to administer gadolinium chelates. APT imaging may provide an added value to [¹⁸F]FDG PET in the evaluation of tumor metabolic activity during brain PET/MR studies.

PET imaging in glioma: techniques and current evidence

PET holds potential to provide additional information about tumour metabolic processes, which could aid brain tumour differential diagnosis, grading, molecular subtyping and/or the distinction of therapy effects from disease recurrence. This review discusses PET techniques currently in use for untreated and treated glioma characterization and aims to critically assess the evidence for different tracers ([F]Fluorodeoxyglucose, choline and amino acid tracers) in this context.

Feasibility of multi-parametric PET and MRI for prediction of tumour recurrence in patients with glioblastoma

BACKGROUND

Recurrence in glioblastoma patients often occur close to the original tumour and indicates that the current treatment is inadequate for local tumour control. In this study, we explored the feasibility of using multi-modality imaging at the time of radiotherapy planning. Specifically, we aimed to identify parameters from pre-treatment PET and MRI with potential to predict tumour recurrence.

MATERIALS AND METHODS

Sixteen patients were prospectively recruited and treated according to established guidelines. Multi-parametric imaging with ¹⁸F-FET PET/CT and ¹⁸F-FDG PET/MR including diffusion and dynamic contrast enhanced perfusion MRI were performed before radiotherapy. Correlations between imaging parameters were calculated. Imaging was related to the voxel-wise outcome at the time of tumour recurrence. Within the radiotherapy target, median differences of imaging parameters in recurring and non-recurring voxels were calculated for contrast-enhancing lesion (CEL), non-enhancing lesion (NEL), and normal appearing grey and white matter. Logistic regression models were created to predict the patient-specific probability of recurrence. The most important parameters were identified using standardized model coefficients.

RESULTS

Significant median differences between recurring and non-recurring voxels were observed for FDG, FET, fractional anisotropy, mean diffusivity, mean transit time, extra-vascular, extra-cellular blood volume and permeability derived from scans prior to chemo-radiotherapy. Tissue-specific patterns of voxel-wise correlations were observed. The most pronounced correlations were observed for ¹⁸F-FDG- and ¹⁸F-FET-uptake in CEL and NEL. Voxel-wise modelling of recurrence probability resulted in area under the receiver operating characteristic curve of 0.77 from scans prior to therapy. Overall, FET proved to be the most important parameter for recurrence prediction.

CONCLUSION

Multi-parametric imaging before radiotherapy is feasible and significant differences in imaging parameters between recurring and non-recurring voxels were observed. Combining parameters in a logistic regression model enabled patient-specific maps of recurrence probability, where ¹⁸F-FET proved to be most important. This strategy could enable risk-adapted radiotherapy planning.

Prediction of Overall Survival Based on Isocitrate Dehydrogenase 1 Mutation and 18F-FDG Uptake on PET/CT in Patients With Cerebral Gliomas

PURPOSE

This retrospective study aimed to correlate F-FDG uptake on PET/CT with isocitrate dehydrogenase enzyme isoform 1 (IDH1) mutation in patients with cerebral gliomas. Hierarchical interactions between factors affecting overall survival (OS) were also examined.

METHODS

In 59 patients with glioma, the ratio of the SUVmax of a glioma to the SUVmean of the contralateral cortex (G/C ratio) on F-FDG PET/CT and the presence of IDH1 mutation were correlated. The prognostic value of clinicopathologic factors and G/C ratio for OS were assessed using a Cox proportional hazards model and classification and regression tree models.

RESULTS

The mean G/C ratio of IDH1-mutant tumors was significantly lower than that of IDH1 wild-type tumors (0.73 vs 1.14, P = 0.004). In multivariate analysis, IDH1-mutant and G/C ratio were significant for OS. The classification and regression tree modeling identified 3 risk groups for OS (group 1: IDH1 mutant [hazard ratio, 0.2]; group 2: G/C ratio ≤0.8 with IDH1 wild type [hazard ratio, 0.83]; group 3: G/C ratio >0.8 with IDH1 wild type [hazard ratio, 1.9]) (overall P < 0.001). The mean OS was 37.0 months in group 1, 28.6 months in group 2, and 20.7 months in group 3, respectively, showing significant differences among the groups (group 1 vs group 2: P = 0.023, group 2 vs group 3: P = 0.049, group 1 vs group3: P < 0.001).

CONCLUSIONS

F-FDG uptake of IDH1-mutant gliomas was significantly lower than that of IDH1 wild-type gliomas. IDH1 mutation was the most important factor in identifying patients with the best prognosis, whereas increased F-FDG uptake provided additional prognostic information for predicting poor OS among patients with IDH1 wild-type gliomas.

Clinical PET/MRI: 2018 Update

OBJECTIVE

The purpose of this article is to provide an update on clinical PET/MRI, including current and developing clinical indications and technical developments.

CONCLUSION

PET/MRI is evolving rapidly, transitioning from a predominant research focus to exciting clinical practice. Key technical obstacles have been overcome, and further technical advances promise to herald significant advancements in image quality. Further optimization of protocols to address challenges posed by this hybrid modality will ensure the long-term success of PET/MRI.

18F-FDG PET/CT in immunocompetent patients with primary central nervous system lymphoma: Differentiation from glioblastoma and correlation with DWI

OBJECTIVES

¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is useful for the detection of cancerous lesions, and FDG uptake is related to the apparent diffusion coefficient (ADC) derived from diffusion-weighted imaging (DWI) of extracranial tumors. The purpose of our study was to investigate the ability of FDG PET/CT in distinguishing primary central nervous system lymphoma (PCNSL) from glioblastoma multiforme (GBM) and to explore the relationship between ¹⁸F-FDG uptake and the ADC in patients with PCNSL.

METHODS

We reviewed 92 patients (40 with PCNSL and 52 with GBM) who underwent FDG PET/CT scans at disease onset. The maximum standardized uptake value (SUVmax), tumor to normal contralateral cortex activity (T/N) ratio, SUVmean, metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of tumor lesions were calculated. Receiver operating characteristic (ROC) curves were generated to determine the diagnostic performance for FDG PET-related parameters to differentiate PCNSL from GBM. Twenty-eight patients with PCNSL (with 34 lesions) also underwent diffusion-weighted imaging. Pearson's correlation analysis was used to assess the relation between SUV- and ADC-derived parameters.

RESULTS

The SUVmax, T/N ratio, SUVmean, and TLG values were significantly higher in PCNSL than in GBM. Comparative ROC analysis indicated that the SUVmax had a greater area under the curve (AUC) of 0.910 than the T/N ratio (0.905, P = .85), SUVmean (0.836, P = .0006), or TLG (0.641, P < 0.0001). The T/N ratio had the highest specificity (94.23%) for differentiating PCNSL from GBM, while the SUVmax had the most optimal sensitivity (92.31%). Further combined analysis of the indices did not significantly improve the AUC. Moderate inverse correlations between the SUVmax, SUVmean, TLG, and the ADC ratio (rADC) were found in PCNSLs (r = -0.526, P = .002; r = -0.504, P = .004; and r = -0.483, P = .006; respectively).

CONCLUSIONS

The SUVmax and T/N ratio may be reliable measures for differentiating PCNSLs from GBMs. Additionally, FDG metabolism indices were inversely proportional to the rADCs of PCNSL lesions.

A surgical strategy using a fusion image constructed from 11C-methionine PET, 18F-FDG-PET and MRI for glioma with no or minimum contrast enhancement

The objective of this study was to investigate the distribution of 11C-methionine (MET) and F-18 fluorodeoxyglucose (FDG) uptake in positron emission tomography (PET) imaging and the hyperintense area in T2 weighted imaging (T2WI) in glioma with no or poor gadolinium enhancement in magnetic resonance imaging (GdMRI). Cases were also analyzed pathologically. We prospectively investigated 16 patients with non- or minimally enhancing (< 10% volume) glioma. All patients underwent MET-PET and FDG-PET scans preoperatively. After delineating the tumor based on MET uptake, integrated 3D images from FDG-PET and MRI (GdMRI, T2WI or FLAIR) were generated and the final resection plane was planned. This resection plane was determined intraoperatively using the navigation-guided fencepost method. The delineation obtained by MET-PET imaging was larger than that with GdMRI in all cases with an enhanced effect. In contrast, the T2WI-abnormal signal area (T2WI+) tended to be larger than the MET uptake area (MET+). Tumor resection was > 95% in the non-eloquent area in 4/5 cases (80%), whereas 10 of 11 cases (90.9%) had partial resection in the eloquent area. In a case including the language area, 92% resection was achieved based on the MET-uptake area, in contrast to T2WI-based partial resection (65%), because the T2WI+/MET- area defined the language area. Pathological findings showed that the T2WI+/MET+ area is glioma, whereas 6 of 9 T2WI+/MET- lesions included normal tissues. Tissue from T2W1+/MET+/FDG+/GdMRI+ lesions gave an accurate diagnosis of grade in six cases. Non- or minimally enhancing gliomas were classified as having a MET uptake area that totally or partially overlapped with the T2WI hyperintense area. Resection planning with or without a metabolically active area in non- or minimally enhancing gliomas may be useful for accurate diagnosis, malignancy grading, and particularly for eloquent area although further study is needed to analyze the T2WI+/MET- area.

The roles of 11C-acetate PET/CT in predicting tumor differentiation and survival in patients with cerebral glioma

PURPOSE

This prospective study aimed to evaluate the clinical values of ¹¹C-acetate positron emission tomography/computed tomography (PET/CT) in predicting histologic grades and survival in patients with cerebral glioma.

METHODS

Seventy-three patients with surgically confirmed cerebral gliomas (19 grade II, 21 grade III, and 33 grade IV) who underwent ¹¹C-acetate PET/CT before surgery were included. Tumor-to-choroid plexus ratio (TCR), which was defined as the maximum standardized uptake value (SUV) of tumors to the mean SUV of choroid plexus, was compared between three World Health Organization (WHO) grade groups. Moreover, metabolic tumor volumes (MTV) were calculated. Progression-free survival (PFS) and overall survival (OS) curves were plotted using the Kaplan-Meier method, and differences in survival between groups were assessed using the log-rank test.

RESULTS

Median TCR was 1.20 (interquartile range [IQR], 1.14 to 1.4) in grade II, 1.65 (IQR, 1.26 to 1.79) in grade III, and 2.53 (IQR, 1.93 to 3.30) in grade IV gliomas. Significant differences in TCR were seen among the three WHO grade groups (P < 0.001). In Cox regression analysis including TCR, MTV, molecular markers, and other clinical factors, TCR was prognostic for PFS (P = 0.016) and TCR and MTV were prognostic for OS (P = 0.024 [TCR], P = 0.030 [MTV]). PFS and OS were significantly shorter in patients with a TCR ≥ 1.6 than in those with a TCR < 1.6. OS were significantly shorter in patients with a MTV ≥ 1 than in those with a TCR < 1.

CONCLUSIONS

TCR on ¹¹C-acetate PET/CT significantly differed between low- and high-grade cerebral gliomas, and it showed the capability to further differentiate grade III from grade IV tumors. TCR and MTV were independent prognostic factors and predicted survival better than did the WHO grade.

Magnetic Resonance Spectroscopy, Positron Emission Tomography and Radiogenomics-Relevance to Glioma

Advances in metabolic imaging techniques have allowed for more precise characterization of gliomas, particularly as it relates to tumor recurrence or pseudoprogression. Furthermore, the emerging field of radiogenomics where radiographic features are systemically correlated with molecular markers has the potential to achieve the holy grail of neuro-oncologic neuro-radiology, namely molecular diagnosis without requiring tissue specimens. In this section, we will review the utility of metabolic imaging and discuss the current state of the art related to the radiogenomics of glioblastoma.

Correlation between hypoxic area in primary brain tumors and WHO grade: differentiation from malignancy using 18F-fluoromisonidazole positron emission tomography

Background 18F-fluoromisonidazole positron emission tomography (FMISO-PET) has been used for identification of hypoxic areas in tumors, and since hypoxia causes hypoxia-inducible factor-1 and enhancement of tumor growth, identifying the hypoxic area in the tumor tissue is important. Purpose To evaluate the usefulness of FMISO-PET in the grading of primary brain tumors. Material and Methods FMISO-PET was performed preoperatively on 41 consecutive patients with pathologically confirmed brain tumor. A neuroradiologist retrospectively measured both maximum standardized uptake value (SUVmax) and mean SUV (SUVmean) in the tumor and normal cerebellar parenchyma. Maximum tumor/normal control ratio (T/Nmax) and mean tumor/normal control ratio (T/Nmean) were calculated and analyzed. Results There was a positive correlation between World Health Organization (WHO) grade and both T/Nmax and T/Nmean (r = 0.731 and 0.713, respectively). When all cases were divided into benign (WHO grade II) and malignant groups (III and IV), there were significant differences between the two groups in both T/Nmax and T/Nmean ( P < 0.001). If the cutoff value was defined as T/Nmax = 1.25 and T/Nmean = 1.23, T/Nmax had a sensitivity of 90.0% and a specificity of 90.9% while T/Nmean had a sensitivity of 93.3% and a specificity of 90.9% in differentiating the benign group from the malignant group. Conclusion Both T/Nmax and T/Nmean in FMISO-PET have a positive correlation with primary brain tumor grading, making FMISO-PET useful in diagnosing the malignancy of primary brain tumors.

Current Radiopharmaceuticals for Positron Emission Tomography of Brain Tumors

Brain tumors represent a diverse spectrum of histology, biology, prognosis, and treatment options. Although MRI remains the gold standard for morphological tumor characterization, positron emission tomography (PET) can play a critical role in evaluating disease status. This article focuses on the use of PET with radiolabeled glucose and amino acid analogs to aid in the diagnosis of tumors and differentiate between recurrent tumors and radiation necrosis. The most widely used tracer is ¹⁸F-fluorodeoxyglucose (FDG). Although the intensity of FDG uptake is clearly associated with tumor grade, the exact role of FDG PET imaging remains debatable. Additionally, high uptake of FDG in normal grey matter limits its use in some low-grade tumors that may not be visualized. Because of their potential to overcome the limitation of FDG PET of brain tumors, ¹¹C-methionine and ¹⁸F-3,4-dihydroxyphenylalanine (FDOPA) have been proposed. Low accumulation of amino acid tracers in normal brains allows the detection of low-grade gliomas and facilitates more precise tumor delineation. These amino acid tracers have higher sensitivity and specificity for detecting brain tumors and differentiating recurrent tumors from post-therapeutic changes. FDG and amino acid tracers may be complementary, and both may be required for assessment of an individual patient. Additional tracers for brain tumor imaging are currently under development. Combinations of different tracers might provide more in-depth information about tumor characteristics, and current limitations may thus be overcome in the near future. PET with various tracers including FDG, ¹¹C-methionine, and FDOPA has improved the management of patients with brain tumors. To evaluate the exact value of PET, however, additional prospective large sample studies are needed.

Tracking Functional Tumor Cell Subpopulations of Malignant Glioma by Phasor Fluorescence Lifetime Imaging Microscopy of NADH

Intra-tumoral heterogeneity is associated with therapeutic resistance of cancer and there exists a need to non-invasively identify functional tumor subpopulations responsible for tumor recurrence. Reduced nicotinamide adenine dinucleotide (NADH) is a metabolic coenzyme essential in cellular respiration. Fluorescence lifetime imaging microscopy (FLIM) of NADH has been demonstrated to be a powerful label-free indicator for inferring metabolic states of living cells. Using FLIM, we identified a significant shift towards longer NADH fluorescence lifetimes, suggesting an increase in the fraction of protein-bound NADH, in the invasive stem-like tumor-initiating cell (STIC) subpopulation relative to the tumor mass-forming cell (TMC) subpopulation of malignant gliomas. By applying our previously studied model to transition glioma from a majority of STIC to a majority of TMC in serum-adherent culture conditions following serial passages, we compared changes in NADH states, cellular respirations (oxidative phosphorylation and glycolysis), EGFR expression, and cell-growth speed over passages. We identified a significant positive correlation between free-NADH fraction and cell growth, which was related to an increase of TMC fraction. In comparison, the increase of EGFR and cellular respirations preceded all these changes. In conclusion, FLIM of NADH provides a non-invasive method to monitor the dynamics of tumor heterogeneity before and after treatment.

Sexual dimorphism in glioma glycolysis underlies sex differences in survival

The molecular bases for sex differences in cancer remain undefined and how to incorporate them into risk stratification remains undetermined. Given sex differences in metabolism and the inverse correlation between fluorodeoxyglucose (FDG) uptake and survival, we hypothesized that glycolytic phenotyping would improve glioma subtyping. Using retrospectively acquired lower-grade glioma (LGG) transcriptome data from The Cancer Genome Atlas (TCGA), we discovered male-specific decreased survival resulting from glycolytic gene overexpression. Patients within this high-glycolytic group showed significant differences in the presence of key genomic alterations (i.e., 1p/19q codeletion, CIC, EGFR, NF1, PTEN, FUBP1, and IDH mutations) compared with the low-glycolytic group. Although glycolytic stratification defined poor prognostic males independent of grade, histology, TP53, and ATRX mutation status, we unexpectedly found that females with high-glycolytic gene expression and wild-type IDH survived longer than all other wild-type patients. Validation with an independent metabolomics dataset from grade 2 gliomas determined that glycolytic metabolites selectively stratified males and also uncovered a potential sexual dimorphism in pyruvate metabolism. These findings identify a potential synergy between patient sex, tumor metabolism, and genomic alterations in determining outcome for glioma patients.

Vibrational Profiling of Brain Tumors and Cells

This study reports vibration profiles of neuronal cells and tissues as well as brain tumor and neocortical specimens. A contact-free method and analysis protocol was designed to convert an atomic force microscope into an ultra-sensitive microphone with capacity to record and listen to live biological samples. A frequency of 3.4 Hz was observed for both cultured rat hippocampal neurons and tissues and vibration could be modulated pharmacologically. Malignant astrocytoma tissue samples obtained from operating room, transported in artificial cerebrospinal fluid, and tested within an hour, vibrated with a much different frequency profile and amplitude, compared to meningioma or lateral temporal cortex providing a quantifiable measurement to accurately distinguish the three tissues in real-time. Vibration signals were converted to audible sound waves by frequency modulation, thus demonstrating, acoustic patterns unique to meningioma, malignant astrocytoma and neocortex.

Neurologic Applications of PET/MR Imaging

PET/MR imaging benefits neurologic clinical care and research by providing spatially and temporally matched anatomic MR imaging, advanced MR physiologic imaging, and metabolic PET imaging. MR imaging sequences and PET tracers can be modified to target physiology specific to a neurologic disease process, with applications in neurooncology, epilepsy, dementia, cerebrovascular disease, and psychiatric and neurologic research. Simultaneous PET/MR imaging provides efficient acquisition of multiple temporally matched datasets, and opportunities for motion correction and improved anatomic assignment of PET data. Current challenges include optimizing MR imaging-based attenuation correction and necessity for dual expertise in PET and MR imaging.

Correlation of 18F-FDG PET and MRI Apparent Diffusion Coefficient Histogram Metrics with Survival in Diffuse Intrinsic Pontine Glioma: A Report from the Pediatric Brain Tumor Consortium

The purpose of this study was to describe baseline ¹⁸F-FDG PET voxel characteristics in pediatric diffuse intrinsic pontine glioma (DIPG) and to correlate these metrics with baseline MRI apparent diffusion coefficient (ADC) histogram metrics, progression-free survival (PFS), and overall survival. Methods: Baseline brain ¹⁸F-FDG PET and MRI scans were obtained in 33 children from Pediatric Brain Tumor Consortium clinical DIPG trials. ¹⁸F-FDG PET images, postgadolinium MR images, and ADC MR images were registered to baseline fluid attenuation inversion recovery MR images. Three-dimensional regions of interest on fluid attenuation inversion recovery MR images and postgadolinium MR images and ¹⁸F-FDG PET and MR ADC histograms were generated. Metrics evaluated included peak number, skewness, and kurtosis. Correlation between PET and MR ADC histogram metrics was evaluated. PET pixel values within the region of interest for each tumor were plotted against MR ADC values. The association of these imaging markers with survival was described. Results: PET histograms were almost always unimodal (94%, vs. 6% bimodal). None of the PET histogram parameters (skewness or kurtosis) had a significant association with PFS, although a higher PET postgadolinium skewness tended toward a less favorable PFS (hazard ratio, 3.48; 95% confidence interval [CI], 0.75-16.28 [P = 0.11]). There was a significant association between higher MR ADC postgadolinium skewness and shorter PFS (hazard ratio, 2.56; 95% CI, 1.11-5.91 [P = 0.028]), and there was the suggestion that this also led to shorter overall survival (hazard ratio, 2.18; 95% CI, 0.95-5.04 [P = 0.067]). Higher MR ADC postgadolinium kurtosis tended toward shorter PFS (hazard ratio, 1.30; 95% CI, 0.98-1.74 [P = 0.073]). PET and MR ADC pixel values were negatively correlated using the Pearson correlation coefficient. Further, the level of PET and MR ADC correlation was significantly positively associated with PFS; tumors with higher values of ADC-PET correlation had more favorable PFS (hazard ratio, 0.17; 95% CI, 0.03-0.89 [P = 0.036]), suggesting that a higher level of negative ADC-PET correlation leads to less favorable PFS. A more significant negative correlation may indicate higher-grade elements within the tumor leading to poorer outcomes. Conclusion:¹⁸F-FDG PET and MR ADC histogram metrics in pediatric DIPG demonstrate different characteristics with often a negative correlation between PET and MR ADC pixel values. A higher negative correlation is associated with a worse PFS, which may indicate higher-grade elements within the tumor.

Progressive multifocal exophytic pontine glioblastoma: a case report with literature review

Multifocal pontine glioblastoma exhibiting an exophytic growth pattern in the cerebello-pontine angle (CPA) is rare. We present a case of a 5-year-old girl with consecutive neurological imaging and other clinical findings indicating progressive multifocal exophytic pontine glioblastoma. Three lesions were reported, of which two were initially presented, and one was developed 2 months later. One lesion demonstrated a progressing exophytic extension in the cistern of the left side of the CPA. The other two lesions were located and confined within the pons. Initial magnetic resonance imaging and positron emission tomography–computed tomography indicated low-grade glioma or inflammatory disease. However, 2 and 3 months later, subsequent magnetic resonance spectroscopy (MRS) displayed elevated choline and depressed N-acetyl aspartate peaks compared with the peaks on the initial MRS, indicating a high-grade glioma. Subtotal resection was performed for the CPA lesion. Histopathologic examination showed discrepant features of different parts of the CPA lesion. The patient received no further chemotherapy or radiotherapy and died 2 months after surgery. The multifocal and exophytic features of this case and the heterogeneous manifestations on neurological images were rare and confusing for both diagnosis and surgical decision-making. Our case report may contribute knowledge and helpful guidance for other medical doctors.

Increased 18F-2-Fluorodeoxysorbitol (18F-FDS) Activity in a Pituitary Spindle Cell Carcinoma

A 33-year-old woman presented with progressive visual loss. An MRI examination revealed a pituitary lesion which was suspicious of abscess. FDG and F-2-fluorodeoxysorbitol (F-FDS) PET were performed to differentiate malignancy from inflammation. FDS is a new tracer with potential in differentiating inflammatory tissues based on results from animal studies. However, intense tracer uptake was found in the pituitary in both PET studies. The lesion was proved to be spindle cell carcinoma following biopsy.

Re-Examining the Need for Tissue Diagnosis in Pediatric Diffuse Intrinsic Pontine Gliomas: A Review

Diffuse intrinsic pontine glioma (DIPG) is a malignant brain tumor of childhood that carries an extremely poor prognosis. There are ~200-300 new cases diagnosed each year, [1, 2] and little progress has been made in changing the prognosis and outcome of the tumor since it was first documented in the literature in 1926 [3]. The median overall survival is 8-11 months [4], with an overall survival rate of 30% at 1 year, and less than 10% at 2 years [4]. This review will provide background information on DIPGs, a historical look at the trends in caring for DIPG, and current trends in diagnosis and treatment. By changing the way we care for these terminal tumors, we can work towards having a better understanding of the underlying molecular biology, and attempt to develop better chemotherapeutic tools to combat the disease.

PET/CT in paediatric malignancies - An update

¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) is a well-established imaging modality in adult oncological practice. Its role in childhood malignancies needs to be discussed as paediatric malignancies differ from adults in tumor subtypes and they have different tumor biology and FDG uptake patterns. This is also compounded by smaller body mass, dosimetric restrictions, and physiological factors that can affect the FDG uptake. It calls for careful planning of the PET study, preparing the child, the parents, and expertise of nuclear physicians in reporting pediatric positron emission tomography/computed tomography (PET/CT) studies. In a broad perspective, FDG-PET/CT has been used in staging, assessment of therapy response, identifying metastases and as a follow-up tool in a wide variety of pediatric malignancies. This review outlines the role of PET/CT in childhood malignancies other than hematological malignancies such as lymphoma and leukemia.