Late-line treatment with bevacizumab alone or in combination with chemotherapy in recurrent high-grade gliomas.

PURPOSE: Bevacizumab's use in recurrent high-grade glioma is controversial. This study evaluates outcomes in recurrent high-grade glioma patients receiving bevacizumab alone or combined with chemotherapy as a late-line treatment. METHODS: We retrospectively analyzed patients treated with bevacizumab alone or combined with chemotherapy for high-grade gliomas who showed tumor progression after multiple treatment attempts. Overall survival (OS) and progression-free survival (PFS) were analyzed with Kaplan-Meier curves. Predictors of PFS according to prognostic variables were assessed with regression analysis. RESULTS: Between 2010 and 2022, 31 consecutive patients received bevacizumab alone or combined with chemotherapy as a late-line treatment for recurrent high-grade gliomas. Of these patients, 14 (45.2%) were responders according to RANO criteria, and 17 (54.8%) showed progressive or stable disease. OS at 3, 6, and 12 months was 80.3%, 62.1%, and 43.5. PFS was 48.4%, 34.3%, and 21.8%, respectively. In the multivariate survival analysis, the only factor independently associated with PFS was smaller 2D tumor size in post-contrast T1-weighted MRI at bevacizumab initiation (p = 0.02). Median time-to-progression was 3 months (95%CI: 1-4) in the unmethylated MGMT promoter group and 6 (95%CI: 1-11) in the methylated MGMT promoter group. This difference was not statistically significant (p = 0.37). CONCLUSIONS: Bevacizumab alone or in combination with chemotherapy could be beneficial as a late-line therapy in a subset of patients with recurrent high-grade glioma. Small 2D tumor size in post-contrast T1 weighted MRI at bevacizumab initiation was independently associated with prolonged time to progression.

Effects of alcohol exposure on the glutamatergic system: a combined longitudinal 18 F-FPEB and 1 H-MRS study in rats.

In a longitudinal rat model of alcohol consumption, we showed that exposure to alcohol decreased the concentration of glutamate in the prefrontal cortex, whereas a normalization occurred during abstinence. 18F-FPEB PET scans revealed that pre-exposure mGluR5 availability in the nucleus accumbens was associated with future alcohol preference. Finally, alcohol exposure induced a decrease in mGluR5 availability in the bilateral hippocampus and amygdala compared with baseline, and in the hippocampus and striatum compared with saccharin (Figure).

Cerebral dopaminergic and glutamatergic transmission relate to different subjective responses of acute alcohol intake: an in vivo multimodal imaging study.

Converging preclinical evidence links extrastriatal dopamine release and glutamatergic transmission via the metabotropic glutamate receptor 5 (mGluR5) to the rewarding properties of alcohol. To date, human evidence is lacking on how and where in the brain these processes occur. Mesocorticolimbic dopamine release upon intravenous alcohol administration and mGluR5 availability were measured in 11 moderate social drinkers by single-session [18 F]fallypride and [18 F]FPEB positron emission tomography, respectively. Additionally, baseline and postalcohol glutamate and glutamine levels in the anterior cingulate cortex (ACC) were measured by using proton-magnetic resonance spectroscopy. To investigate differences in reward domains linked to both neurotransmitters, regional imaging data were related to subjective alcohol responses. Alcohol induced significant [18 F]fallypride displacement in the prefrontal cortex (PFC), temporal and parietal cortices and thalamus (P < 0.05, corrected for multiple comparisons). Dopamine release in the ACC and orbitofrontal and ventromedial PFCs were correlated with subjective 'liking' and 'wanting' effects (P < 0.05). In contrast, baseline mGluR5 availability was positively correlated with the 'high' effect of alcohol in dorsolateral, ventrolateral and ventromedial PFCs and in the medial temporal lobe, thalamus and caudate nucleus (P < 0.05). Although neither proton-magnetic resonance spectroscopy glutamate nor glutamine levels were affected by alcohol, baseline ACC glutamate levels were negatively associated with the alcohol 'liking' effect (P < 0.003). These data reveal new mechanistic understanding and differential neurobiological underpinnings of the effects of acute alcohol consumption on human behavior. Specifically, prefrontal dopamine release may encode alcohol 'liking' and 'wanting' effects in specific areas underlying value processing and motivation, whereas mGluR5 availability in distinct prefrontal-temporal-subcortical regions is more related to the alcohol 'high' effect.

Kinetic modeling and long-term test-retest reproducibility of the mGluR5 PET tracer 18F-FPEB in human brain.

(18)F-FPEB is a promising PET tracer for studying the metabotropic glutamate subtype 5 receptor (mGluR5) expression in neuropsychiatric disorders. To assess the potential of (18)F-FPEB for longitudinal mGluR5 evaluation in patient studies, we evaluated the long-term test-retest reproducibility using various kinetic models in the human brain. Nine healthy volunteers underwent consecutive scans separated by a 6-month period. Dynamic PET was combined with arterial sampling and radiometabolite analysis. Total distribution volume (V(T)) and nondisplaceable binding potential (BP(ND)) were derived from a two-tissue compartment model without constraints (2TCM) and with constraining the K(1)/k(2) ratio to the value of either cerebellum (2TCM-CBL) or pons (2TCM-PONS). The effect of fitting different functions to the tracer parent fractions and reducing scan duration were assessed. Regional absolute test-retest variability (aTRV), coefficient of repeatability (CR) and intraclass correlation coefficient (ICC) were computed. The 2TCM-CBL showed best fits. The mean 6-month aTRV of V(T) ranged from 8 to 13% (CR < 25%) with ICC > 0.6 for all kinetic models. BPND from 2TCM-CBL with a sigmoid fit for the parent fractions showed the best reproducibility, with aTRV ≤ 7% (CR < 16%) and ICC > 0.9 in most regions. Reducing the scan duration from 90 to 60 min did not affect reproducibility. These results demonstrate for the first time that (18)F-FPEB brain PET has good long-term reproducibility, therefore validating its use to monitor mGluR5 expression in longitudinal clinical studies. We suggest a 2TCM-CBL with fitting a sigmoid function to the parent fractions to be optimal for this tracer.

Clinical experience with 18F-JK-PSMA-7 when using a digital PET/CT.

BACKGROUND: Digital PET/CT systems make use of a new technology with higher sensitivity and other better technological features than the analog ones. They require adaptation of the trade-off between performance, tracer dose and acquisition time. The aim of the study was to explore the performance of 18F-JK-PSMA-7 imaging when performed on a digital PET/CT with an adapted protocol, in a population of patients with prostate cancer patients (PCa). Influence of previous therapy on PET/CT performance is generally disregarded in PSMA-based imaging, despite potential influence of hormono-chemotherapy on the target expression. This potential influence was also tested in this work. METHODS: A total of 54 PCa patients experiencing biochemical recurrence were included in the study, in which we analysed the diagnostic performance of digital 18F-JK-PSMA-7 PET/CT. Compared to our protocol applied for acquisition on an analog system, administered dose and acquisition time were reduced by 20% and 50% respectively. We specifically took into consideration the influence of previous treatments on recurrence detection. RESULTS: We detected overall 18F-JK-PSMA-7-positive lesions in 38/54 patients (70.3%). There was no statistically significant difference regarding the detection rate between the groups of patients who had hormono-chemotherapy any time after initial diagnosis and those who never got any hormonal or chemotherapeutic treatment. Regarding the SUV max values, there was not significant difference between the two groups of patients neither in pelvic ganglions nor in other metastatic sites or the prostate region. CONCLUSION: 18F-JK-PSMA7 PET/CT with administered dose and acquisition time adapted to the digital technology provides valuable information in PCa patients with biochemical recurrence.

Diffuse pancreatic lesion mimicking autoimmune pancreatitis in an HIV-infected patient: successful treatment by antiretroviral therapy.

CONTEXT: Pancreatitis is a common complication of acquired immunodeficiency syndrome. The most common causes of acute pancreatitis in an HIV population are medication and opportunistic infections. CASE REPORT: We report the case of a young, untreated, HIV-infected female who presented with acute pancreatitis of unknown origin. Unique to this case are the autoimmune pancreatitis-like features on imaging studies associated with renal mass-like lesions and lymph node involvement as well as the favorable outcome using highly active antiretroviral therapy alone. CONCLUSION: In HIV-infected patients, acute pancreatitis may present on imaging studies as autoimmune pancreatitis. In patients with uncontrolled HIV infection and imaging studies suggestive of autoimmune pancreatitis, direct HIV-related inflammation should be considered after exclusion of all other causes of pancreatitis.

Voxelwise Principal Component Analysis of Dynamic [S-Methyl-11C]Methionine PET Data in Glioma Patients.

Recent works have demonstrated the added value of dynamic amino acid positron emission tomography (PET) for glioma grading and genotyping, biopsy targeting, and recurrence diagnosis. However, most of these studies are based on hand-crafted qualitative or semi-quantitative features extracted from the mean time activity curve within predefined volumes. Voxelwise dynamic PET data analysis could instead provide a better insight into intra-tumor heterogeneity of gliomas. In this work, we investigate the ability of principal component analysis (PCA) to extract relevant quantitative features from a large number of motion-corrected [S-methyl-11C]methionine ([11C]MET) PET frames. We first demonstrate the robustness of our methodology to noise by means of numerical simulations. We then build a PCA model from dynamic [11C]MET acquisitions of 20 glioma patients. In a distinct cohort of 13 glioma patients, we compare the parametric maps derived from our PCA model to these provided by the classical one-compartment pharmacokinetic model (1TCM). We show that our PCA model outperforms the 1TCM to distinguish characteristic dynamic uptake behaviors within the tumor while being less computationally expensive and not requiring arterial sampling. Such methodology could be valuable to assess the tumor aggressiveness locally with applications for treatment planning and response evaluation. This work further supports the added value of dynamic over static [11C]MET PET in gliomas.

Recovery of Decreased Metabotropic Glutamate Receptor 5 Availability in Abstinent Alcohol-Dependent Patients.

Animal models of alcohol dependence and relapse demonstrate an important role of the glutamatergic system, in particular, cerebral metabotropic glutamate receptor 5 (mGluR5). 18F-3-fluoro-5-[(pyridin-3-yl)ethynyl]benzonitrile (18F-FPEB) PET has revealed that chronic alcohol use leads to decreased limbic mGluR5 availability, which was associated with less craving. Here, we tested whether the state of decreased mGluR5 availability in alcohol-dependent patients normalizes during abstinence (at 2 and 6 mo of detoxification) and whether initial mGluR5 imaging parameters can predict individual relapse. Methods:18F-FPEB scans were performed for 16 recently detoxified alcohol-dependent patients (baseline condition), 2 mo after detoxification (n = 10), and 6 mo after detoxification (n = 8); 32 age- and sex-matched controls were included for comparison. mGluR5 availability was quantified by the 18F-FPEB total distribution volume using both voxel-by-voxel and volume-of-interest analyses. During follow-up, craving was assessed using the Desire for Alcohol Questionnaire, and alcohol consumption was assessed using the timeline follow-back method and monitored by hair ethyl glucuronide analysis. Results: During abstinence, alcohol-dependent patients showed sustained recovered mGluR5 availability in cortical and subcortical regions compared with the baseline, up to the levels observed in controls, after 6 mo in most areas except for the hippocampus, nucleus accumbens, and thalamus. Higher striatopallidal mGluR5 availability was observed at the baseline in patients who had a relapse during the 6-mo follow-up period (+25.1%). Also, normalization of striatal mGluR5 to control levels was associated with reduced craving ("desire and intention to drink" and "negative reinforcement"; r = 0.72-0.94). Conclusion: Reduced cerebral mGluR5 availability in alcohol-dependent patients recovers during abstinence and is associated with reduced craving. Higher striatal mGluR5 availability in alcohol-dependent users may be associated with long-term relapse.

Glutamatergic Biomarkers for Cocaine Addiction: A Longitudinal Study Using MR Spectroscopy and mGluR5 PET in Self-Administering Rats.

Cocaine addiction is a disorder that still lacks diagnostic biomarkers or effective pharmacotherapy. We present findings on a rat model of cocaine self-administration that was followed up longitudinally using the metabotropic glutamate receptor type 5 (mGluR5) tracer 18F-3-fluoro-5-[(pyridin-3-yl)ethynyl]benzonitrile (18F-FPEB) PET, proton MR spectroscopy (1H-MRS), and behavioral tests. Methods: Forty-two Wistar rats were scanned with 18F-FPEB PET and 1H-MRS before and after sucrose or intravenous cocaine self-administration, during withdrawal, and during relapse. All animals performed a rodent Iowa Gambling Task (rIGT) at baseline to evaluate decision making. Baseline values were used in a mixed model to assess associations with later cocaine use, and follow-up measurements were compared with the values before drug exposure. Results: Preexposure rIGT scores were significantly related to both cocaine and sucrose use during the drug-exposure phase. However, only cocaine self-administration induced a decrease in 18F-FPEB binding. This decrease was most pronounced bilaterally in the hippocampus, where mGluR5 availability correlated with the amount of cocaine used during relapse. Compared with the sucrose group, a larger decrease was observed in the hippocampo-prefrontal cortex pathway. Preexposure glutamate and glycine concentrations in the prefrontal cortex were significantly associated with cocaine use during the drug-exposure phase. Moreover, prefrontal glutamate exhibited a distinct, reversible decrease when animals had access to cocaine but not sucrose. Conclusion: Baseline values of prefrontal glutamate and glycine are associated with future cocaine use. Furthermore, baseline rIGT scores are associated with both sucrose and cocaine. Finally, both glutamate concentration and mGluR5 availability decrease during exposure to cocaine.

Lower Limbic Metabotropic Glutamate Receptor 5 Availability in Alcohol Dependence.

Animal studies suggest an important role for the metabotropic glutamate receptor subtype 5 (mGlu5) in the pathophysiology of alcohol dependence, but direct human evidence is lacking. The goal of this study was to investigate cerebral mGlu5 availability in alcohol-dependent subjects versus controls using 18F-3-fluoro-5-[(pyridin-3-yl)ethynyl]benzonitrile (18F-FPEB) PET. Methods: Dynamic 90-min 18F-FPEB scans combined with arterial blood sampling were acquired for 16 recently abstinent alcohol-dependent subjects and 32 age-matched controls. Regional mGlu5 availability was quantified by the 18F-FPEB total distribution volume using both a voxel-by-voxel and a volume-of-interest analysis with partial-volume effect correction. Alcohol consumption within the last 3 mo was assessed by questionnaires and by hair ethyl glucuronide analysis. Craving was assessed using the Desire for Alcohol Questionnaire. Results: mGlu5 availability was lower in mainly limbic regions of alcohol-dependent subjects than in controls (P < 0.05, familywise error-corrected), ranging from 14% in the posterior cingulate cortex to 36% in the caudate nucleus. Lower mGlu5 availability was associated with higher hair ethyl glucuronide levels for most regions and was related to a lower level of craving specifically in the middle frontal gyrus, cingulate cortex, and inferolateral temporal lobe. Conclusion: These findings provide human in vivo evidence that limbic mGlu5 has a role in the pathophysiology of alcohol dependence, possibly involved in a compensatory mechanism helping to reduce craving during abstinence.

What We Observe In Vivo Is Not Always What We See In Vitro: Development and Validation of 11C-JNJ-42491293, A Novel Radioligand for mGluR2.

Positive allosteric modulators (PAM) of metabotropic glutamate receptor 2 (mGluR2) are a potential therapy for anxiety, schizophrenia, and addiction. Aside from pathophysiologic imaging studies, an mGluR2 PET tracer would enable confirmation of sufficient central target engagement and assist dose selection for proof-of-concept studies of PAM compounds. 11C-JNJ-42491293, a novel high-affinity radioligand (human 50% inhibitory concentration = 9.6 nM) for the PAM site of mGluR2, was evaluated as a selective mGluR2 PAM PET tracer. METHODS: In vitro and ex vivo autoradiography binding experiments in Wistar and in mGluR2 knockout and wildtype rats as well as in vivo biodistribution and brain PET imaging studies in wildtype and mGluR2 knockout rats in a primate and in humans were performed. RESULTS: In vitro binding studies and in vivo imaging studies in Wistar rats showed moderate brain uptake, with a distribution pattern fully consistent with the reported intracerebral distribution of mGluR2. Given these promising findings, biodistribution, dosimetry, and brain kinetic modeling of 11C-JNJ-42491293 were determined in humans. Because of an unexpected high myocardial retention, additional 11C-JNJ-42491293 imaging studies were performed in recently available mGluR2 knockout and wildtype rats and in a monkey using a structurally distinct mGluR2 PAM ligand with affinity for the same site, demonstrating off-target binding in vivo that could not have been anticipated from previous in vitro experiments. To date, the target of this non-mGluR2 tracer binding remains unknown. CONCLUSION: On the basis of in vivo selectivity issues suggested by human distribution and demonstrated in knockout rat models, 11C-JNJ-42491293 was considered unsuitable as a specific PET ligand for in vivo imaging of mGluR2. These results emphasize the importance of elaborated in vitro/in vivo comparative studies and, when available, validation with knockout animal models or structurally distinct ligands with affinity for the same site, in radiotracer development.

Positive Association Between Limbic Metabotropic Glutamate Receptor 5 Availability and Novelty-Seeking Temperament in Humans: An 18F-FPEB PET Study.

Heritable temperament traits have been linked to several neuropsychiatric illnesses, including disorders associated with metabotropic glutamate receptor 5 (mGluR5) and dopaminergic dysfunctions. Considering its modulating effect on neurotransmission, we hypothesized that cerebral mGluR5 availability is associated with temperament traits in healthy humans. METHODS: Forty-four nonsmoking healthy volunteers (mean age ± SD, 40 ± 14 y; age range, 22-66 y; 22 women) were included in this cross-sectional investigation. Brain mGluR5 availability was quantified on both a voxel-by-voxel and a volume-of-interest basis using the total distribution volume of the radioligand 18F-3-fluoro-5-[(pyridin-3-yl)ethynyl]benzonitrile (18F-FPEB) with 90-min dynamic PET and arterial input function. Moreover, glutamate-glutamine concentrations in the anterior cingulate cortex were measured using MR spectroscopy. These measures were related to the temperament traits of the 240-item Cloninger temperament and character inventory using a regression analysis with age and sex as nuisance variables. RESULTS: High novelty-seeking temperament was robustly associated with increased mGluR5 availability in various regions including the thalamus (r = 0.71; the strongest association), amygdala, parahippocampus, insula, anterior and posterior cingulate cortex, and several primary sensory areas (all r > 0.58; P < 0.05, corrected for familywise error). These associations were specific because no correlations were found with other temperament scales or with spectroscopic measures of glutamatergic transmission. CONCLUSION: Overall, these data posit mGluR5 in key paralimbic areas as a strong determinant of the temperament trait novelty seeking. These data add to our understanding of how brain neurochemistry accounts for the variation in human behavior and strongly support further research on mGluR5 as a potential therapeutic target in neuropsychiatric disorders associated with abnormal novelty-seeking behaviors.

Preclinical Evaluation and Quantification of 18F-FPEB as a Radioligand for PET Imaging of the Metabotropic Glutamate Receptor 5.

UNLABELLED: The metabotropic glutamate receptor 5 (mGluR5) is a high-interest target for PET imaging because it plays a role in several pathologies, including addiction, schizophrenia, and fragile X syndrome. METHODS: We studied the pharmacokinetics of (18)F-FPEB (3-(18)F-fluoro-5-(2-pyridinylethynyl)benzonitrile), a selective PET radioligand for mGluR5, and used it to quantify mGluR5 in rat brain. Quantification was performed using both arterial sampling in combination with compartment models and simplified reference methods. The simplified reference tissue model (SRTM), Ichise's original multi-linear reference tissue model (MRTMO), and Logan noninvasive were tested as reference models with nondisplaceable binding (BPND) as outcome parameter. Additionally, test-retest scans were obtained in 6 animals. RESULTS: (18)F-FPEB uptake in rat brain was consistent with its known distribution. No radiometabolites were present in the brain, and binding was specific as shown in blocking experiments, which also confirmed the cerebellum as a viable reference region. A 2-tissue-compartment model was used to determine BPND for the striatum (11.7 ± 1.5), nucleus accumbens (10.6 ± 2.0), hippocampus (9.0 ± 1.2), cortex (7.2 ± 1.0), and thalamus (4.0 ± 0.9). Reference methods were able to estimate these values with small bias (<2%). Test-retest analysis showed high repeatability between scans below 6%, also for shorter scan durations of 30 and 60 min. CONCLUSION: Because of its favorable reversible kinetics, high specificity, and absence of brain radiometabolites (18)F-FPEB proves a highly useful tracer for in vivo visualization of the mGluR5 in rat brain. Moreover, reference tissue models allow noninvasive, rapid scanning with good test-retest.

Improvement in lung diffusion by endothelin A receptor blockade at high altitude.

Lung diffusing capacity has been reported variably in high-altitude newcomers and may be in relation to different pulmonary vascular resistance (PVR). Twenty-two healthy volunteers were investigated at sea level and at 5,050 m before and after random double-blind intake of the endothelin A receptor blocker sitaxsentan (100 mg/day) vs. a placebo during 1 wk. PVR was estimated by Doppler echocardiography, and exercise capacity by maximal oxygen uptake (Vo(2 max)). The diffusing capacities for nitric oxide (DL(NO)) and carbon monoxide (DL(CO)) were measured using a single-breath method before and 30 min after maximal exercise. The membrane component of DL(CO) (Dm) and capillary volume (Vc) was calculated with corrections for hemoglobin, alveolar volume, and barometric pressure. Altitude exposure was associated with unchanged DL(CO), DL(NO), and Dm but a slight decrease in Vc. Exercise at altitude decreased DL(NO) and Dm. Sitaxsentan intake improved Vo(2 max) together with an increase in resting and postexercise DL(NO) and Dm. Sitaxsentan-induced decrease in PVR was inversely correlated to DL(NO). Both DL(CO) and DL(NO) were correlated to Vo(2 max) at sea level (r = 0.41-0.42, P < 0.1) and more so at altitude (r = 0.56-0.59, P < 0.05). Pharmacological pulmonary vasodilation improves the membrane component of lung diffusion in high-altitude newcomers, which may contribute to exercise capacity.