(11)C-Methionine uptake in secondary brain epilepsy

Investigation of Cerebral O-(2-[18F]Fluoroethyl)-L-Tyrosine Uptake in Rat Epilepsy Models

PURPOSE

A recent study reported on high, longer lasting and finally reversible cerebral uptake of O-(2-[¹⁸F]fluoroethyl)-L-tyrosine ([¹⁸F]FET) induced by epileptic activity. Therefore, we examined cerebral [¹⁸F]FET uptake in two chemically induced rat epilepsy models and in patients with focal epilepsy to further investigate whether this phenomenon represents a major pitfall in brain tumor diagnostics and whether [¹⁸F]FET may be a potential marker to localize epileptic foci.

PROCEDURES

Five rats underwent kainic acid titration to exhibit 3 to 3.5 h of class IV-V motor seizures (status epilepticus, SE). Rats underwent 4× [¹⁸F]FET PET and 4× MRI on the following 25 days. Six rats underwent kindling with pentylenetetrazol (PTZ) 3 to 8×/week over 10 weeks, and hence, seizures increased from class I to class IV. [¹⁸F]FET PET and MRI were performed regularly on days with and without seizures. Four rats served as healthy controls. Additionally, five patients with focal epilepsy underwent [¹⁸F]FET PET within 12 days after the last documented seizure.

RESULTS

No abnormalities in [¹⁸F]FET PET or MRI were detected in the kindling model. The SE model showed significantly decreased [¹⁸F]FET uptake 3 days after SE in all examined brain regions, and especially in the amygdala region, which normalized within 2 weeks. Corresponding signal alterations in T₂-weighted MRI were noted in the amygdala and hippocampus, which recovered 24 days post-SE. No abnormality of cerebral [¹⁸F]FET uptake was noted in the epilepsy patients.

CONCLUSIONS

There was no evidence for increased cerebral [¹⁸F]FET uptake after epileptic seizures neither in the rat models nor in patients. The SE model even showed decreased [¹⁸F]FET uptake throughout the brain. We conclude that epileptic seizures per se do not cause a longer lasting increased [¹⁸F]FET accumulation and are unlikely to be a major cause of pitfall for brain tumor diagnostics.

Molecular Imaging of Brain Tumor-Associated Epilepsy

Epilepsy is a common clinical manifestation and a source of significant morbidity in patients with brain tumors. Neuroimaging has a pivotal role in neuro-oncology practice, including tumor detection, differentiation, grading, treatment guidance, and posttreatment monitoring. In this review, we highlight studies demonstrating that imaging can also provide information about brain tumor-associated epileptogenicity and assist delineation of the peritumoral epileptic cortex to optimize postsurgical seizure outcome. Most studies focused on gliomas and glioneuronal tumors where positron emission tomography (PET) and advanced magnetic resonance imaging (MRI) techniques can detect metabolic and biochemical changes associated with altered amino acid transport and metabolism, neuroinflammation, and neurotransmitter abnormalities in and around epileptogenic tumors. PET imaging of amino acid uptake and metabolism as well as activated microglia can detect interictal or peri-ictal cortical increased uptake (as compared to non-epileptic cortex) associated with tumor-associated epilepsy. Metabolic tumor volumes may predict seizure outcome based on objective treatment response during glioma chemotherapy. Advanced MRI, especially glutamate imaging, can detect neurotransmitter changes around epileptogenic brain tumors. Recently, developed PET radiotracers targeting specific glutamate receptor types may also identify therapeutic targets for pharmacologic seizure control. Further studies with advanced multimodal imaging approaches may facilitate development of precision treatment strategies to control brain tumor-associated epilepsy.

Central Nervous System Metastasis in Patients With Urothelial Carcinoma: Institutional Experience and a Comprehensive Review of the Literature

INTRODUCTION

Central nervous system (CNS) metastasis in patients with urothelial carcinoma (UC) is uncommon and poorly understood. We aimed to explore the clinical behavior and outcomes of this unique patient population.

MATERIALS AND METHODS

We performed a retrospective analysis of patients with UC and CNS metastasis, treated in our institution (2006-2018), along with an exploratory patient-point meta-analysis of a similar patient population derived from a comprehensive literature review. Data regarding diagnosis, management, and outcomes were extracted. Overall survival, time to CNS metastasis (TTCM), and residual survival (RS) from CNS involvement to death were calculated (Kaplan-Meier method). Cox regression was used for testing key clinicopathologic associations.

RESULTS

We identified 20 "institutional" and 154 "literature" patients with adequate data granularity for analysis. Median TTCM was 17.7 (institutional cohort) and 10 (literature cohort) months. Most patients who developed CNS metastases had previous non-CNS metastasis (15/20 [75%] and 103/154 [67%], respectively). CNS lesions without previous history of metastasis were identified in 5/20 (25%) and 33/154 (21%) cases and those patients had a shorter TTCM. CNS lesions in the absence of known UC history were also documented in 18/154 (12%) literature cases. Multifocal CNS disease was associated with shorter RS in both cohorts in univariate, but not multivariate, analysis.

CONCLUSION

We observed a variability in disease presentation and course, with a subset of patients showing an early predilection for CNS insult, potentially reflecting a diverse underlying biology. Genomic profiling studies, elucidating the molecular landscape, and driving future treatments should be considered in this setting.

Joint EANM/EANO/RANO practice guidelines/SNMMI procedure standards for imaging of gliomas using PET with radiolabelled amino acids and [18F]FDG: version 1.0

These joint practice guidelines, or procedure standards, were developed collaboratively by the European Association of Nuclear Medicine (EANM), the Society of Nuclear Medicine and Molecular Imaging (SNMMI), the European Association of Neurooncology (EANO), and the working group for Response Assessment in Neurooncology with PET (PET-RANO). Brain PET imaging is being increasingly used to supplement MRI in the clinical management of glioma. The aim of these standards/guidelines is to assist nuclear medicine practitioners in recommending, performing, interpreting and reporting the results of brain PET imaging in patients with glioma to achieve a high-quality imaging standard for PET using FDG and the radiolabelled amino acids MET, FET and FDOPA. This will help promote the appropriate use of PET imaging and contribute to evidence-based medicine that may improve the diagnostic impact of this technique in neurooncological practice. The present document replaces a former version of the guidelines published in 2006 (Vander Borght et al. Eur J Nucl Med Mol Imaging. 33:1374–80, 2006), and supplements a recent evidence-based recommendation by the PET-RANO working group and EANO on the clinical use of PET imaging in patients with glioma (Albert et al. Neuro Oncol. 18:1199–208, 2016). The information provided should be taken in the context of local conditions and regulations.