Enhancing predictability of IDH mutation status in glioma patients at initial diagnosis: a comparative analysis of radiomics from MRI, [18F]FET PET, and TSPO PET

PURPOSE

According to the World Health Organization classification for tumors of the central nervous system, mutation status of the isocitrate dehydrogenase (IDH) genes has become a major diagnostic discriminator for gliomas. Therefore, imaging-based prediction of IDH mutation status is of high interest for individual patient management. We compared and evaluated the diagnostic value of radiomics derived from dual positron emission tomography (PET) and magnetic resonance imaging (MRI) data to predict the IDH mutation status non-invasively.

METHODS

Eighty-seven glioma patients at initial diagnosis who underwent PET targeting the translocator protein (TSPO) using [18F]GE-180, dynamic amino acid PET using [18F]FET, and T1-/T2-weighted MRI scans were examined. In addition to calculating tumor-to-background ratio (TBR) images for all modalities, parametric images quantifying dynamic [18F]FET PET information were generated. Radiomic features were extracted from TBR and parametric images. The area under the receiver operating characteristic curve (AUC) was employed to assess the performance of logistic regression (LR) classifiers. To report robust estimates, nested cross-validation with five folds and 50 repeats was applied.

RESULTS

TBRGE-180 features extracted from TSPO-positive volumes had the highest predictive power among TBR images (AUC 0.88, with age as co-factor 0.94). Dynamic [18F]FET PET reached a similarly high performance (0.94, with age 0.96). The highest LR coefficients in multimodal analyses included TBRGE-180 features, parameters from kinetic and early static [18F]FET PET images, age, and the features from TBRT2 images such as the kurtosis (0.97).

CONCLUSION

The findings suggest that incorporating TBRGE-180 features along with kinetic information from dynamic [18F]FET PET, kurtosis from TBRT2, and age can yield very high predictability of IDH mutation status, thus potentially improving early patient management.

What MRI Sequences are Necessary for Automated Neural Network-Based Metastasis Segmentation - An Ablation Study

PURPOSE/OBJECTIVE(S)

Brain metastasis (BM) delineation is a time-consuming process in both daily clinical practice and research. Automated BM segmentation algorithms can be used to assist in this task. Most approaches to brain tumor segmentation, such as algorithms trained on the BraTS challenge, use four magnetic resonance imaging (MRI) sequences as input, making them susceptible to missing or corrupted sequences and increase the number of sequences necessary for MRI RT planning. The goal of this project is to compare neural networks with different combinations of input sequences for the segmentation of the contrast-enhancing metastasis and the surrounding FLAIR hyperintense edema. All models were tested in a multicenter international external test cohort. This allows us to determine which MRI sequences are needed for effective automated segmentations.

MATERIALS/METHODS

In total, we had T1-weighted sequences without (T1) and with contrast enhancement (T1-CE), T2-weighted sequences (T2), and T2 fluid-attenuated inversion recovery (FLAIR) sequences from 339 patients with at least one brain metastasis from seven centers available. Preprocessing yielded co-registered, skull-stripped sequences with an isotropic resolution of 1 millimeter. The contrast-enhancing metastasis as well as the surrounding FLAIR hyperintense edema were manually segmented to create reference labels. A baseline 3D U-Net with all four sequences as well as six additional U-Nets with different clinically plausible combinations (T1-CE; T1; FLAIR; T1-CE+FLAIR; T1-CE+T1+FLAIR; T1-CE+T1) of input sequences were trained on a cohort of 239 patients from two centers and subsequently tested on an external cohort of 100 patients from the remaining five centers.

RESULTS

All models that included T1-CE in their selected sequences showed similar performance for metastasis segmentation with a median Dice similarity coefficient (DSC) of 0.93-0.96. T1-CE alone likewise achieved a performance of 0.96 (IQR 0.93-0.97). The model trained with only FLAIR performed worse (DSC = 0.73, IQR 0.54-0.84). For edema segmentation, models that included both T1-CE and FLAIR performed best (median DSC = 0.93), while the remaining four models without simultaneous inclusion of these two sequences (T1-CE; T1; FLAIR; T1-CE+T1) reached a median DSC of 0.81-0.89.

CONCLUSION

Automatic segmentation of brain metastases with less than four input sequences is feasible with minimal or no loss of quality. A T1-CE-only protocol suffices for metastasis segmentation. In contrast, for edema segmentation, the combination of T1-CE and FLAIR seems to be important. Missing either T1-CE or FLAIR decreases performance. These findings may improve future imaging routines by omitting unnecessary sequences, thus speeding up procedures in daily clinical practice while allowing for optimal neural network-based target definitions.

Hypofractionated Stereotactic Radiotherapy vs. Single Fraction Stereotactic Radiosurgery to the Resection Cavity of Brain Metastases after Surgical Resection (SATURNUS trial): A Prospective, Randomized Phase III Trial

PURPOSE/OBJECTIVE(S)

The brain is a common site for metastases. Resection of large or symptomatic metastases is followed by stereotactic radiotherapy to prevent local recurrence. The optimal fractionation scheme is subject of ongoing research. Supported by emerging retrospective data, we hypothesize that hypofractionated stereotactic radiotherapy (HFSRT) is superior to single-fraction stereotactic radiosurgery (SRS) in terms of local control (LC). We designed the SATURNUS trial to prospectively demonstrate the superiority of HFSRT over SRS after resection of brain metastases in terms of LC.

MATERIALS/METHODS

The SATURNUS trial is a prospective, randomized phase III trial, currently recruiting patients at a single institution. Patients are 1:1 allocated to HFSRT or SRS using permuted block randomization. Affiliation to the treatment arm is solely blinded to the neuroradiologist assessing therapy response. HFSRT will be delivered with 6 - 7 x 5 Gy and SRS with 1 x 12-20 Gy, prescribed to the surrounding isodose, depending on cavity size and proximity to structures at risk. For SRS, doses do not exceed the maximum doses according to RTOG 90-05. Case number calculation was based on own institutional data on HFSRT (mean LC rate of 88% at 12 months) and data from large phase III trials on SRS (pooled mean LC rate of 66% at 12 months). Using a Chi-squared test of equal proportions (odds ratio = 1), setting test significance level (α) to 0.05, and allocating an equal number of patients to both treatment arms, 114 patients are needed to detect the superiority of HFSRT in terms of LC at 12 months (primary endpoint) with a power of at least 80%. Estimating a dropout rate of 10%, the case number was set to 126. The trial was registered with clinicaltrials.gov (NCT05160818). The first patient was enrolled in May 2021 and recruitment is ongoing. Patients with up to three resected brain metastases are considered for study participation. Further eligibility criteria are histologically confirmed solid tumor disease, resection cavity diameter ≤ 4 cm, consent to perform adjuvant radiotherapy by an interdisciplinary tumor board, completed wound healing, resection within the last six weeks at the time of study inclusion, age ≥ 18 years, KPS ≥ 60%, adequate contraceptive measures for fertile women / men and written informed consent. Patients are followed up clinically and with MRI at 6 weeks and 3, 6, 9 and 12 months after treatment. LC is assessed according to RANO-BM. Toxicity (CTCAE v4.03) is assessed as a secondary endpoint. The rather broad dose corridors allowed within the trial do justice to clinical reality, however, may represent a limitation of the trial. They are therefore addressed with a predefined subgroup analysis, as will be cavity size, among others. Participation of further study centers is desired. To the best of our knowledge, the SATURNUS trial is the only randomized phase III trial adequately powered to detect the superiority of HFSRT over SRS with regard to LC for resected brain metastases.

RESULTS

To be determined.

CONCLUSION

To be determined.

Multicenter Evaluation of AI-generated DIR and PSIR for Cortical and Juxtacortical Multiple Sclerosis Lesion Detection

Background Cortical multiple sclerosis lesions are clinically relevant but inconspicuous at conventional clinical MRI. Double inversion recovery (DIR) and phase-sensitive inversion recovery (PSIR) are more sensitive but often unavailable. In the past 2 years, artificial intelligence (AI) was used to generate DIR and PSIR from standard clinical sequences (eg, T1-weighted, T2-weighted, and fluid-attenuated inversion-recovery sequences), but multicenter validation is crucial for further implementation. Purpose To evaluate cortical and juxtacortical multiple sclerosis lesion detection for diagnostic and disease monitoring purposes on AI-generated DIR and PSIR images compared with MRI-acquired DIR and PSIR images in a multicenter setting. Materials and Methods Generative adversarial networks were used to generate AI-based DIR (n = 50) and PSIR (n = 43) images. The number of detected lesions between AI-generated images and MRI-acquired (reference) images was compared by randomized blinded scoring by seven readers (all with >10 years of experience in lesion assessment). Reliability was expressed as the intraclass correlation coefficient (ICC). Differences in lesion subtype were determined using Wilcoxon signed-rank tests. Results MRI scans of 202 patients with multiple sclerosis (mean age, 46 years ± 11 [SD]; 127 women) were retrospectively collected from seven centers (February 2020 to January 2021). In total, 1154 lesions were detected on AI-generated DIR images versus 855 on MRI-acquired DIR images (mean difference per reader, 35.0% ± 22.8; P < .001). On AI-generated PSIR images, 803 lesions were detected versus 814 on MRI-acquired PSIR images (98.9% ± 19.4; P = .87). Reliability was good for both DIR (ICC, 0.81) and PSIR (ICC, 0.75) across centers. Regionally, more juxtacortical lesions were detected on AI-generated DIR images than on MRI-acquired DIR images (495 [42.9%] vs 338 [39.5%]; P < .001). On AI-generated PSIR images, fewer juxtacortical lesions were detected than on MRI-acquired PSIR images (232 [28.9%] vs 282 [34.6%]; P = .02). Conclusion Artificial intelligence-generated double inversion-recovery and phase-sensitive inversion-recovery images performed well compared with their MRI-acquired counterparts and can be considered reliable in a multicenter setting, with good between-reader and between-center interpretative agreement. Published under a CC BY 4.0 license. Supplemental material is available for this article. See also the editorial by Zivadinov and Dwyer in this issue.

Reconstruction of the Corticospinal Tract in Patients with Motor-Eloquent High-Grade Gliomas Using Multilevel Fiber Tractography Combined with Functional Motor Cortex Mapping

BACKGROUND AND PURPOSE

Tractography of the corticospinal tract is paramount to presurgical planning and guidance of intraoperative resection in patients with motor-eloquent gliomas. It is well-known that DTI-based tractography as the most frequently used technique has relevant shortcomings, particularly for resolving complex fiber architecture. The purpose of this study was to evaluate multilevel fiber tractography combined with functional motor cortex mapping in comparison with conventional deterministic tractography algorithms.

MATERIALS AND METHODS

Thirty-one patients (mean age, 61.5 [SD, 12.2] years) with motor-eloquent high-grade gliomas underwent MR imaging with DWI (TR/TE = 5000/78 ms, voxel size = 2 × 2 × 2 mm3, 1 volume at b = 0 s/mm2, 32 volumes at b = 1000 s/mm2). DTI, constrained spherical deconvolution, and multilevel fiber tractography-based reconstruction of the corticospinal tract within the tumor-affected hemispheres were performed. The functional motor cortex was enclosed by navigated transcranial magnetic stimulation motor mapping before tumor resection and used for seeding. A range of angular deviation and fractional anisotropy thresholds (for DTI) was tested.

RESULTS

For all investigated thresholds, multilevel fiber tractography achieved the highest mean coverage of the motor maps (eg, angular threshold = 60°; multilevel/constrained spherical deconvolution/DTI, 25% anisotropy threshold = 71.8%, 22.6%, and 11.7%) and the most extensive corticospinal tract reconstructions (eg, angular threshold = 60°; multilevel/constrained spherical deconvolution/DTI, 25% anisotropy threshold = 26,485 mm3, 6308 mm3, and 4270 mm3).

CONCLUSIONS

Multilevel fiber tractography may improve the coverage of the motor cortex by corticospinal tract fibers compared with conventional deterministic algorithms. Thus, it could provide a more detailed and complete visualization of corticospinal tract architecture, particularly by visualizing fiber trajectories with acute angles that might be of high relevance in patients with gliomas and distorted anatomy.

Methylation subgroup and molecular heterogeneity is a hallmark of glioblastoma: implications for biopsy targeting, classification and therapy

Background

Patients and methods

Results

Conclusions

•

Glioblastoma exhibits significant heterogeneity, from epigenome-wide methylation phenotypes to single molecular targets.

•

Phylogeny showed CDKN2A/B loss and gain of EGFR, PDGFRA, and CDK4 early in tumor development.

•

Intratumoral heterogeneity is of utmost importance for molecular classification as well as for defining therapeutic targets.

•

Assessing single biopsies underestimates the true molecular diversity in a tumor.

P11.22.A Prognostic and predictive relevance of immunohistochemically determined p53 mutation in glioblastoma

Background

It can be expected that molecular biomarkers will increasingly affect clinical decisions and lead to the development of more personalized therapies in glioblastoma (GBM) in the future. In several other tumor entities TP53 gene mutation or p53 immunoreactivity (IR) serve as a prognostic marker, significantly affecting overall survival (OS) and progression-free survival (PFS). Such an association has not yet sufficiently been demonstrated in GBM. However, there are known prognostic markers in GBM, notably MGMT promotor methylation (mMGMT) which also serves as an important predictive marker leading to a better response to temozolomide chemotherapy. Our aim was to evaluate retrospectively if p53 mutation determined via immunohistochemistry (IHC) could act as a prognostic or predictive marker in GBM.

Material and Methods

Tumor samples of 195 treatment-naïve patients with IDHwt GBM that had been stained with the p53 antibody DO-7 were subdivided into 2 different groups by p53 IHC. Samples were considered as p53mut when strong p53 IR was detected in ≥10% of all tumor cells and as p53wt when in &lt;10%. Treatment, further molecular and survival data were gathered retrospectively for all patients. Statistical analyses were performed with SPSS.

Results

The frequency of p53mut was 36.4% (71/195). p53mut tumors showed a significantly higher IR with Ki-67 proliferation marker (p=0.005) and p53wt seemed to be associated with multifocal primary tumor localization, though not statistically significant (p=0.107). There was no significant difference between p53wt and p53mut regarding gender, age, extent of resection, adjuvant therapy, occurrence of seizures, mMGMT or ATRX loss. The p53 status was not associated with OS or PFS. Factors that univariately led to significantly longer OS and PFS were younger age, unilateral or unifocal primary tumor localization, gross-total resection, higher Karnofsky Performance Status (KPS), mMGMT and adjuvant treatment via Stupp regimen instead of radiotherapy alone, the latter being significantly better than best supportive care. In multivariate survival analyses only age &lt;65 years, the Stupp regimen more than radiotherapy alone and KPS ≥80% significantly prolonged both OS and PFS. Unifocal primary tumor localization led to longer OS and mMGMT led to longer PFS independently. The p53 status did not significantly affect the response to different adjuvant therapy regimens neither concerning OS nor PFS.

Conclusion

Based on our study, p53 IR has no prognostic or predictive significance in IDHwt GBM. There have been previous studies with similar and others with contradicting results. Remarkable is the discordance of the used IR thresholds between different studies. Further studies should aim to revalidate the staining threshold and improve the concordance between TP53 gene sequencing and p53 IHC in IDHwt GBM.

Differential Effects of Fingolimod and Natalizumab on Magnetic Resonance Imaging Measures in Relapsing-Remitting Multiple Sclerosis

Fingolimod and natalizumab are approved disease-modifying drugs in relapsing-remitting multiple sclerosis (RRMS). The two drugs have different modes of action and may therefore influence different aspects of MS-related tissue damage. In this retrospective cohort study, we longitudinally compared patients treated with fingolimod and patients treated with natalizumab by measures based on structural magnetic resonance imaging (MRI). We included patients with RRMS given that two standardized MRI scans under the same drug were available with an interval of at least 6 months both from therapy start to baseline scan and from baseline scan to follow-up scan. After matching for age, baseline and follow-up scans from 93 patients (fingolimod, 48; natalizumab, 45) were investigated. Mean follow-up time was 1.9 years. We determined the number of new white matter lesions as well as thalamic, cortical, and whole-brain atrophy. After scaling for time of the interscan interval, measures were analyzed by group comparisons and, to account for demographic and clinical characteristics, by multiple regression models and a binary logistic regression model. Compared to natalizumab, fingolimod treatment went along with more new white matter lesions (median [interquartile range, IQR] 0.0 [0.0; 0.7] vs. 0.0 [0.0; 0.0] /year; p < 0.01) whereas whole-brain atrophy was lower (median [IQR] 0.2 [0.0; 0.5] vs. 0.5 [0.2; 1.0] %/year; p = 0.01). These significant differences were confirmed by multiple regression models and the binary logistic regression model. In conclusion, our observation is compatible with stronger neuroprotective properties of fingolimod compared to natalizumab.

Imaging glioma biology: spatial comparison of amino acid PET, amide proton transfer, and perfusion-weighted MRI in newly diagnosed gliomas

PURPOSE

Imaging glioma biology holds great promise to unravel the complex nature of these tumors. Besides well-established imaging techniques such O-(2-[18F]fluoroethyl)-L-tyrosine (FET)-PET and dynamic susceptibility contrast (DSC) perfusion imaging, amide proton transfer-weighted (APTw) imaging has emerged as a promising novel MR technique. In this study, we aimed to better understand the relation between these imaging biomarkers and how well they capture cellularity and vascularity in newly diagnosed gliomas.

METHODS

Preoperative MRI and FET-PET data of 46 patients (31 glioblastoma and 15 lower-grade glioma) were segmented into contrast-enhancing and FLAIR-hyperintense areas. Using established cutoffs, we calculated hot-spot volumes (HSV) and their spatial overlap. We further investigated APTw and CBV values in FET-HSV. In a subset of 10 glioblastoma patients, we compared cellularity and vascularization in 34 stereotactically targeted biopsies with imaging.

RESULTS

In glioblastomas, the largest HSV was found for APTw, followed by PET and CBV (p < 0.05). In lower-grade gliomas, APTw-HSV was clearly lower than in glioblastomas. The spatial overlap of HSV was highest between APTw and FET in both tumor entities and regions. APTw correlated significantly with cellularity, similar to FET, while the association with vascularity was more pronounced in CBV and FET.

CONCLUSIONS

We found a relevant spatial overlap in glioblastomas between hotspots of APTw and FET both in contrast-enhancing and FLAIR-hyperintense tumor. As suggested by earlier studies, APTw was lower in lower-grade gliomas compared with glioblastomas. APTw meaningfully contributes to biological imaging of gliomas.

Neoadjuvant stereotactic radiosurgery for intracerebral metastases of solid tumors (NepoMUC): a phase I dose escalation trial

Background

More than 25% of patients with solid cancers develop intracerebral metastases. Aside of surgery, radiation therapy (RT) is a mainstay in the treatment of intracerebral metastases. Postoperative fractionated stereotactic RT (FSRT) to the resection cavity of intracerebral metastases is a treatment of choice to reduce the risk of local recurrence. However, FSRT has to be delayed until a sufficient wound healing is attained; hence systemic therapy might be postponed. Neoadjuvant stereotactic radiosurgery (SRS) might offer advantages over adjuvant FSRT in terms of better target delineation and an earlier start of systemic chemotherapy. Here, we conducted a study to find the maximum tolerated dose (MTD) of neoadjuvant SRS for intracerebral metastases.

Methods

This is a single-center, phase I dose escalation study on neoadjuvant SRS for intracerebral metastases that will be conducted at the Klinikum rechts der Isar Hospital, Technical University of Munich. The rule-based traditional 3 + 3 design for this trial with 3 dose levels and 4 different cohorts depending on lesion size will be applied. The primary endpoint is the MTD for which no dose-limiting toxicities (DLT) occur. The adverse events of each participant will be evaluated according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 continuously during the study until the first follow-up visit (4–6 weeks after surgery). Secondary endpoints include local control rate, survival, immunological tumor characteristics, quality of life (QoL), CTCAE grade of late clinical, neurological, and neurocognitive toxicities. In addition to the intracerebral metastasis which is treated with neoadjuvant SRS and resection up to four additional intracerebral metastases can be treated with definitive SRS. Depending on the occurrence of DLT up to 72 patients will be enrolled. The recruitment phase will last for 24 months.

Discussion

Neoadjuvant SRS for intracerebral metastases offers potential advantages over postoperative SRS to the resection cavity, such as better target volume definition with subsequent higher efficiency of eliminating tumor cells, and lower damage to surrounding healthy tissue, and much-needed systemic chemotherapy could be initiated more rapidly.

Trial registration The local ethical review committee of Technical University of Munich (199/18S) approved this study on September 05, 2018. This trial was registered on German Clinical Trials Register (DRKS00016613; https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00016613) on January 29, 2019.

P14.52 Differential methylation of a single CpG site in the CD95 ligand promoter affects gene activity and correlates with invasiveness of glioma cells

BACKGROUND

CD95 ligand (TNFSF6/APO-1L/FASLG) is a member of the Tumour Necrosis Factor Super Family (TNF-SF). Binding of the CD95 ligand (CD95L) to CD95 expressed on intrinsically apoptosis-resistant cancer cells like glioblastoma, triggers intracellular signal transduction resulting in increased tumour growth and invasiveness. A phase II clinical trial in patients with recurrent glioblastoma (NCT01071837) treated by Asunercept (a recombinant glycosylated fusion protein, which selectively binds and inhibits CD95L activity) was followed by a genome-wide assessment of DNA methylation. Here, a CpG-site (designated CpG2) within the CD95L-promotor was identified, exhibiting differential methylation between Asunercept responders (PFS>5 months) and non-responders (PFS < 2 months) with a significant survival benefit achieved in Asunercept treated patients with low CpG2 methylation (HR 0.34, p = 0.025).

METHODS AND RESULTS

We have performed in vitro studies to establish a link between the CpG2 methylation status and cellular characteristics of glioblastoma cell lines. A 3-dimensional spheroid invasion assay showed that highly methylated glioma cells like T98G did not grow and invade the surrounding matrix as aggressively compared to spheroids formed from low methylated glioma cells, e.g. U87-MG. Invasive growth of U87-MG spheroids in these assays was suppressed in the presence of Asunercept. A 1 kb fragment of the T98G CD95L promoter was subsequently cloned into a CpG-free reporter gene plasmid. Luciferase-based reporter gene assays of in vitro methylated and unmethylated plasmids in transfected HEK cells indicate that the CD95L promoter, despite the observed sparseness of CpG sites, is at least partially regulated by its methylation level. Furthermore, mutational disruption of the CpG2 site completely silenced reporter gene activity in vitro, which insinuates that both methylation level and gene promoter sequence are involved in regulation of the CD95L gene.

CONCLUSION

In essence, the level of CpG2 methylation correlates to aggressiveness of glioma derived cancer spheroids in vitro, and methylation of the CD95L promoter in glioblastoma tissue from patients might warrant use as a potential biomarker predicting response to therapy with Asunercept. We are currently developing a specific and sensitive assay to quantify CpG2 methylation considered as a companion diagnostic for further clinical studies.

P11.07 LAPTM5 functions as a tumor suppressor via CD40 - NFêB pathway inhibition and represents a potential biomarker for temozolomide sensitivity in CD40 proficient glioblastoma

BACKGROUND

Glioma therapy is challenged by the invasive nature of glioma resulting in tumor recurrence and treatment resistance. Lysosomal protein transmembrane 5 (LAPTM5) was identified to inhibit invasion by screening for invasion-associated genes in glioma. The aim of this study was to decipher the function of LAPTM5 in glioblastoma and its interaction with the CD40 receptor which was shown to be highly expressed in up to 40% of glioblastoma.

METHODS

LAPTM5 expression was correlated with clinical outcome of glioma patients. Knockdown of LAPTM5 was performed in different glioma cell lines to analyze the impact on clonogenicity, invasiveness, sensitivity to temozolomide chemotherapy and tumorigenicity in-vitro and in-vivo in a subcutaneous xenograft mouse model. Expression array was used to elucidate the underlying pathways. CD40 knockdown and overexpression was induced to prove the crosstalk of LAPTM5 and CD40.

RESULTS

LAPTM5 expression correlated with better overall survival in high grade glioma patients and acted as a tumor suppressor in CD40 positive glioblastoma cells. LAPTM5 inhibited CD40-mediated NFκB activation resulting in anti-invasive, anti-clonogenic and temozolomide sensitizing effects in-vitro and in-vivo. Vice-versa, knockdown of LAPTM5 enhanced tumorigenicity by activation of the NFκB pathway which was overcome by NFκB inhibition. Importantly, CD40 expression was required for LAPTM5-mediated tumor suppressive activity.

CONCLUSION

LAPTM5 conveyed tumor suppressive and temozolomide sensitizing effects in CD40-positive glioblastoma by inhibition of CD40-mediated NFκB activation and thereby might provide a reasonable biomarker for sensitivity to temozolomide in CD40-positive glioblastoma.

Discrimination of Different Brain Metastases and Primary CNS Lymphomas Using Morphologic Criteria and Diffusion Tensor Imaging

Purpose: Brain metastases are a common complication of cancer and occur in about 15 - 40 % of patients with malignancies. The aim of this retrospective study was to differentiate between metastases from different primary tumors/CNS lymphyomas using morphologic criteria, fractional anisotropy (FA) and apparent diffusion coefficient (ADC). Materials and Methods: Morphologic criteria such as hemorrhage, cysts, pattern of contrast enhancement and location were reported in 200 consecutive patients with brain metastases/primary CNS lymphomas. FA and ADC values were measured in regions of interest (ROIs) placed in the contrast-enhancing tumor part, the necrosis and the non-enhancing peritumoral region (NEPTR). Differences between histopathological subtypes of metastases were analyzed using non-parametric tests, decision trees and hierarchical clustering analysis. Results: Significant differences were found in morphologic criteria such as hemorrhage or pattern of contrast enhancement. In diffusion measurements, significant differences between the different tumor entities were only found in ADC analyzed in the contrast-enhancing tumor part. Among single tumor entities, primary CNS lymphomas showed significantly lower median ADC values in the contrast-enhancing tumor part (ADC_lymphoma 0.92 [0.83 - 1.07] vs. ADC_{no_lymphoma} 1.35 [1.10 - 1.64] P = 0.001). Further differentiation between types of metastases was not possible using FA and ADC. Conclusion: There were morphologic differences among the main subtypes of brain metastases/CNS lymphomas. However, due to a high variability of common types of metastases and low specificity, prospective differentiation remained challenging. DTI including FA and ADC was not a reliable tool for differentiation between different histopathological subtypes of brain metastases except for CNS lymphomas showing lower ADC values. Biopsy, surgery and staging remain essential for diagnosis. Key Points: • Histopathological subtypes of brain metastases/CNS lymphomas show different morphologic features on MRI• Primary CNS lymphomas show significantly reduced ADC values• DTI is not a reliable tool for differentiation between brain metastases Citation Format: • Bette S, Wiestler B, Delbridge C et al. Discrimination of Different Brain Metastases and Primary CNS Lymphomas Using Morphologic Criteria and Diffusion Tensor Imaging. Fortschr Röntgenstr 2016; 188: 1134 - 1143.

Evaluation of microvascular permeability with dynamic contrast-enhanced MRI for the differentiation of primary CNS lymphoma and glioblastoma: radiologic-pathologic correlation

BACKGROUND AND PURPOSE

Dynamic contrast-enhanced MR imaging can provide in vivo assessment of the microvasculature in intracranial tumors. The aim of the present study was to evaluate the diagnostic performance of dynamic contrast-enhanced MR imaging derived vascular permeability parameters, including the volume transfer constant, the volume of extravascular extracellular space, and the flux rate constant between the extravascular extracellular space and plasma, for the differentiation of primary CNS lymphoma and glioblastoma.

MATERIALS AND METHODS

Sixty glioblastomas and 11 primary central nervous system lymphomas were included. Pretreatment T1-weighted dynamic contrast-enhanced MR imaging with a 3D T1-weighted spoiled gradient-echo sequence was performed on a 3T MR imaging scanner. Perfusion parameters (volume transfer constant, the volume of extravascular extracellular space, and the flux rate constant) were measured on the basis of the Tofts-Kernmode model. The Mann-Whitney U test and receiver operating characteristic analysis were used to compare those parameters between primary central nervous system lymphoma and glioblastoma. Histopathologic correlation of dynamic contrast-enhanced MR imaging findings was performed by using reticulin staining and CD31 immunohistochemistry.

RESULTS

Median volume transfer constant and flux rate constant values were significantly higher in primary central nervous system lymphoma (0.145 ± 0.057 and 0.396 ± 0.088) than in glioblastoma (0.064 ± 0.021 and 0.230 ± 0.058) (P < .001, respectively). Median volume of extravascular extracellular space values did not differ significantly between primary central nervous system lymphoma (0.434 ± 0.165) and glioblastoma (0.319 ± 0.107). On receiver operating characteristic analysis, volume transfer constant had the best discriminative value for differentiating primary central nervous system lymphoma and glioblastoma (threshold, 0.093; sensitivity, 90.9%; specificity, 95.0%). Histopathologic evaluation revealed intact vascular integrity in glioblastoma despite endothelial proliferation, whereas primary central nervous system lymphoma demonstrated destroyed vessel architecture, thereby promoting vascular disintegrity.

CONCLUSIONS

Primary central nervous system lymphoma demonstrated significantly higher volume transfer constant and flux rate constant values compared with glioblastoma, implying a higher vascular permeability in primary central nervous system lymphoma. These findings confirm initial observations from perfusion CT and dynamic contrast-enhanced MR imaging studies, correlating with underlying histopathologic features, and may be useful in distinguishing primary central nervous system lymphoma from glioblastoma.

Yes and PI3K bind CD95 to signal invasion of glioblastoma

Invasion of surrounding brain tissue by isolated tumor cells represents one of the main obstacles to a curative therapy of glioblastoma multiforme. Here we unravel a mechanism regulating glioma infiltration. Tumor interaction with the surrounding brain tissue induces CD95 Ligand expression. Binding of CD95 Ligand to CD95 on glioblastoma cells recruits the Src family member Yes and the p85 subunit of phosphatidylinositol 3-kinase to CD95, which signal invasion via the glycogen synthase kinase 3-beta pathway and subsequent expression of matrix metalloproteinases. In a murine syngeneic model of intracranial GBM, neutralization of CD95 activity dramatically reduced the number of invading cells. Our results uncover CD95 as an activator of PI3K and, most importantly, as a crucial trigger of basal invasion of glioblastoma in vivo.