Mario Löhr

Comparison of the Amino Acid Tracers 18F-FET and 18F-DOPA in High-Grade Glioma Patients

High-grade gliomas (HGGs) are the most common malignant primary tumors of the central nervous system. PET probes of amino acid transport such as O-(2-18F-fluoroethyl)-l-tyrosine (18F-FET), 3,4-dihydroxy-6-18F-fluoro-l-phenylalanine (18F-DOPA), and 11C-methionine (11C-MET) detect primary and recurrent tumors with a high accuracy. 18F-FET is predominantly used in Europe, whereas amino acid transport imaging is infrequently done in the United States. The aim of this study was to determine whether 18F-FET and 18F-DOPA PET/CT provide comparable information in HGG. Methods: Thirty 18F-FET and 18F-DOPA PET/CT scans were obtained before surgery or biopsy in 27 patients with high clinical suspicion for primary or recurrent HGG (5 primary, 22 recurrent tumors). 18F-FET and 18F-DOPA PET/CT images were compared visually and semiquantitatively (maximum standardized uptake value [SUVmax], mean SUV [SUVmean]). Background (SUVmax and SUVmean) and tumor-to-background ratios (TBRs) were calculated for both PET probes. The degree of 18F-DOPA uptake in the basal ganglia (SUVmean) was also assessed. Results: Visual analysis revealed no difference in tumor uptake pattern between the 2 PET probes. The SUVmean and SUVmax for 18F-FET were higher than those of 18F-DOPA (4.0 ± 2.0 and 4.9 ± 2.3 vs. 3.5 ± 1.6 and 4.3 ± 2.0, respectively; all P < 0.001). TBRs for SUVmean but not for SUVmax were significantly higher for 18F-FET than 18F-DOPA (TBR SUVmean: 3.8 ± 1.7 vs. 3.4 ± 1.2, P = 0.004; TBR SUVmax: 3.3 ± 1.6 and 3.0 ± 1.1, respectively; P = 0.086). 18F-DOPA uptake by the basal ganglia was present (SUVmean, 2.6 ± 0.7) but did not affect tumor visualization. Conclusion: Whereas visual analysis revealed no significant differences in uptake pattern for 18F-FET and 18F-DOPA in patients with primary or recurrent HGG, both SUVs and TBRs for SUVmean were significantly higher for 18F-FET. However, regarding tumor delineation, both tracers performed equally well and seem equally feasible for imaging of primary and recurrent HGG. These findings suggest that both PET probes can be used based on availability in multicenter trials.

Combination of peptide receptor radionuclide therapy with fractionated external beam radiotherapy for treatment of advanced symptomatic meningioma

BackgroundExternal beam radiotherapy (EBRT) is the treatment of choice for irresectable meningioma. Due to the strong expression of somatostatin receptors, peptide receptor radionuclide therapy (PRRT) has been used in advanced cases. We assessed the feasibility and tolerability of a combination of both treatment modalities in advanced symptomatic meningioma.Methods10 patients with irresectable meningioma were treated with PRRT (177Lu-DOTA0,Tyr3 octreotate or - DOTA0,Tyr3 octreotide) followed by external beam radiotherapy (EBRT). EBRT performed after PRRT was continued over 5–6 weeks in IMRT technique (median dose: 53.0 Gy). All patients were assessed morphologically and by positron emission tomography (PET) before therapy and were restaged after 3–6 months. Side effects were evaluated according to CTCAE 4.0.ResultsMedian tumor dose achieved by PRRT was 7.2 Gy. During PRRT and EBRT, no side effects > CTCAE grade 2 were noted. All patients reported stabilization or improvement of tumor-associated symptoms, no morphologic tumor progression was observed in MR-imaging (median follow-up: 13.4 months). The median pre-therapeutic SUVmax in the meningiomas was 14.2 (range: 4.3–68.7). All patients with a second PET after combined PRRT + EBRT showed an increase in SUVmax (median: 37%; range: 15%–46%) to a median value of 23.7 (range: 8.0–119.0; 7 patients) while PET-estimated volume generally decreased to 81 ± 21% of the initial volume.ConclusionsThe combination of PRRT and EBRT is feasible and well tolerated. This approach represents an attractive strategy for the treatment of recurring or progressive symptomatic meningioma, which should be further evaluated.

Hypertrophy of the lumbar ligamentum flavum is associated with inflammation-related TGF-β expression

BackgroundDespite the significance of hypertrophy of the ligamentum flavum (HLF) in the disease progress of neurogenic claudication, the cellular mechanisms underlying the gradual fibrotic thickening of the ligamentum flavum remain poorly understood. The aim of our study was to get insight into the contribution of inflammatory mechanisms to the development of hypertrophy.MethodsSpecimens of hypertrophied ligamenta flava were obtained at surgery from 20 patients with acquired lumbar osteoligamentous spinal canal stenosis from the central part of the ligament. Paraffin sections were stained with hematoxylin and eosin and Elastica van Gieson to evaluate extracellular matrix architecture, and immunohistochemistry was performed to characterize the inflammatory reaction and the sources of transforming growth factor beta (TGF-β) expression. Sections of normal ligamenta flava obtained from corresponding anatomical sites and stained in parallel served as a control.ResultsHLF was characterized by a considerable distortion of the elastic matrix and fibrotic transformation by extracellular collagen deposition. All specimens showed highly inflammatory cellular infiltrates confined to regions exhibiting marked degeneration of the elastic matrix composed mainly of macrophages, scattered T lymphocytes, and neovascularization, thus representing a chronic inflammation. Surprisingly, macrophages as well as vascular endothelial cells but not fibroblasts showed a strong expression of TGF-β, a strong inducer of extracellular collagen deposition.ConclusionsMacrophages were identified as a major cellular source of TGF-β in advanced HLF and may perpetuate further hypertrophy. This finding suggests that modulating the immune response locally or systemically could prove to be effective for impeding the disease progress.

68 Ga-Pentixafor-PET/CT for Imaging of Chemokine Receptor 4 Expression in Glioblastoma

Chemokine receptor-4 (CXCR4) has been reported to be overexpressed in glioblastoma (GBM) and to be associated with poor survival. This study investigated the feasibility of non-invasive CXCR4-directed imaging with positron emission tomography/computed tomography (PET/CT) using the radiolabelled chemokine receptor ligand 68Ga-Pentixafor. 15 patients with clinical suspicion on primary or recurrent glioblastoma (13 primary, 2 recurrent tumors) underwent 68Ga-Pentixafor-PET/CT for assessment of CXCR4 expression prior to surgery. O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) PET/CT images were available in 11/15 cases and were compared visually and semi-quantitatively (SUVmax, SUVmean). Tumor-to-background ratios (TBR) were calculated for both PET probes. 68Ga-Pentixafor-PET/CT results were also compared to histological CXCR4 expression on neuronavigated surgical samples. 68Ga-Pentixafor-PET/CT was visually positive in 13/15 cases with SUVmean and SUVmax of 3.0±1.5 and 3.9±2.0 respectively. Respective values for 18F-FET were 4.4±2.0 (SUVmean) and 5.3±2.3 (SUVmax). TBR for SUVmean and SUVmax were higher for 68Ga-Pentixafor than for 18F-FET (SUVmean 154.0±90.7 vs. 4.1±1.3; SUVmax 70.3±44.0 and 3.8±1.2, p<0.01), respectively. Histological analysis confirmed CXCR4 expression in tumor areas with high 68Ga-Pentixafor uptake; regions of the same tumor without apparent 68Ga-Pentixafor uptake showed no or low receptor expression. In this pilot study, 68Ga-Pentixafor retention has been observed in the vast majority of glioblastoma lesions and served as readout for non-invasive determination of CXCR4 expression. Given the paramount importance of the CXCR4/SDF-1 axis in tumor biology, 68Ga-Pentixafor-PET/CT might prove a useful tool for sensitive, non-invasive in-vivo quantification of CXCR4 as well as selection of patients who might benefit from CXCR4-directed therapy.

Tumor-associated macrophages in glioblastoma multiforme-a suitable target for somatostatin receptor-based imaging and therapy?

Background Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults. Tumor-associated macrophages (TAM) have been shown to promote malignant growth and to correlate with poor prognosis. [1,4,7,10-tetraazacyclododecane-NN′,N″,N′″-tetraacetic acid]-d-Phe1,Tyr3-octreotate (DOTATATE) labeled with Gallium-68 selectively binds to somatostatin receptor 2A (SSTR2A) which is specifically expressed and up-regulated in activated macrophages. On the other hand, the role of SSTR2A expression on the cell surface of glioma cells has not been fully elucidated yet. The aim of this study was to non-invasively assess SSTR2A expression of both glioma cells as well as macrophages in GBM. Methods 15 samples of patient-derived GBM were stained immunohistochemically for macrophage infiltration (CD68), proliferative activity (Ki67) as well as expression of SSTR2A. Anti-CD45 staining was performed to distinguish between resident microglia and tumor-infiltrating macrophages. In a subcohort, positron emission tomography (PET) imaging using 68Ga-DOTATATE was performed and the semiquantitatively evaluated tracer uptake was compared to the results of immunohistochemistry. Results The amount of microglia/macrophages ranged from <10% to >50% in the tumor samples with the vast majority being resident microglial cells. A strong SSTR2A immunostaining was observed in endothelial cells of proliferating vessels, in neurons and neuropile. Only faint immunostaining was identified on isolated microglial and tumor cells. Somatostatin receptor imaging revealed areas of increased tracer accumulation in every patient. However, retention of the tracer did not correlate with immunohistochemical staining patterns. Conclusion SSTR2A seems not to be overexpressed in GBM samples tested, neither on the cell surface of resident microglia or infiltrating macrophages, nor on the surface of tumor cells. These data suggest that somatostatin receptor directed imaging and treatment strategies are less promising in GBM.

Occurrence and recurrence of spontaneous chronic subdural haematoma is associated with a factor XIII deficiency

OBJECTIVE In some patients, chronic subdural haematoma (cSDH) appears to occur spontaneously with frequent re-bleeding events. The pathophysiology of this phenomenon is still poorly understood. Because coagulation factor XIII (FXIII) is known to be involved in vascular integrity, endothelial barrier function and wound healing, we evaluated the role of FXIII in spontaneous cSDH. METHODS We prospectively scrutinised the origin of cSDH in 117 patients and identified a subgroup of patients suffering from spontaneous cSDH who were included in this study. We analysed the plasma activity of FXIII and standard coagulation parameters and compared these data to age- and sex-matched healthy controls. We assessed the occurrence of re-bleeding events using clinical and imaging data and compared FXIII activity in patients with and without re-bleeding events. RESULTS Out of 117 cSDH patients, 18 individuals suffered from spontaneous cSDH in this study. The patients with spontaneous cSDH showed significantly lower FXIII activity than the control group (65% [52.75, 80.25] (median [IQR]) vs. 93% [81, 111], P=0.001), whereas standard coagulation parameters did not differ significantly between the groups. Six patients developed re-bleeding events after haematoma evacuation, and these patients expressed significantly lower FXIII activity compared to the other 12 patients (47.5% [33.5, 64] vs. 78.5% [58, 87], P=0.005). The patient group with FXIII≤68.5% differed significantly from the group with FXIII>68.5% when categorised by the occurrence of re-bleeding events (n=6/9 vs. n=0/9, P=0.009). This cut-off value predicted the re-bleeding events with a sensitivity of 100% and a specificity of 75% (positive predictive value: 66%, negative predictive value: 100%). CONCLUSION FXIII deficiency may play a pathophysiological role in spontaneous cSDH, so we suggest investigating FXIII activity because it may predict re-bleeding events after treatment. In individuals with considerably low FXIII activity, FXIII substitution may mitigate the chronic nature of this disease.

Transcriptomic analysis of aggressive meningiomas identifies PTTG1 and LEPR as prognostic biomarkers independent of WHO grade

Meningiomas are frequent central nervous system tumors. Although most meningiomas are benign (WHO grade I) and curable by surgery, WHO grade II and III tumors remain therapeutically challenging due to frequent recurrence. Interestingly, relapse also occurs in some WHO grade I meningiomas. Hence, we investigated the transcriptional features defining aggressive (recurrent, malignantly progressing or WHO grade III) meningiomas in 144 cases. Meningiomas were categorized into non-recurrent (NR), recurrent (R), and tumors undergoing malignant progression (M) in addition to their WHO grade. Unsupervised transcriptomic analysis in 62 meningiomas revealed transcriptional profiles lining up according to WHO grade and clinical subgroup. Notably aggressive subgroups (R+M tumors and WHO grade III) shared a large set of differentially expressed genes (n=332; p<0.01, FC>1.25). In an independent multicenter validation set (n=82), differential expression of 10 genes between WHO grades was confirmed. Additionally, among WHO grade I tumors differential expression between NR and aggressive R+M tumors was affirmed for PTTG1, AURKB, ECT2, UBE2C and PRC1, while MN1 and LEPR discriminated between NR and R+M WHO grade II tumors. Univariate survival analysis revealed a significant association with progression-free survival for PTTG1, LEPR, MN1, ECT2, PRC1, COX10, UBE2C expression, while multivariate analysis identified a prediction for PTTG1 and LEPR mRNA expression independent of gender, WHO grade and extent of resection. Finally, stainings of PTTG1 and LEPR confirmed malignancy-associated protein expression changes. In conclusion, based on the so far largest study sample of WHO grade III and recurrent meningiomas we report a comprehensive transcriptional landscape and two prognostic markers.

Long-term tumor control of spinal dissemination of cerebellar glioblastoma multiforme by combined adjuvant bevacizumab antibody therapy: a case report

BackgroundGlioblastoma multiforme located in the posterior fossa is extremely rare with a frequency up to 3.4%. Compared with glioblastoma of the hemispheres the prognosis of infratentorial glioblastoma seems to be slightly better. Absence of brainstem invasion and low expression rates of epidermal growth factor receptor are described as factors for long-time survival due to the higher radiosensitivity of these tumors.Case presentationIn this case study, we report a German female patient with an exophytic glioblastoma multiforme arising from the cerebellar tonsil and a secondary spinal manifestation. Furthermore, the tumor showed no O (6)-Methylguanine-DNA methyltransferase promotor-hypermethylation and no isocitrate dehydrogenase 1 mutations. All these signs are accompanied by significantly shorter median overall survival. A long-term tumor control of the spinal metastases was achieved by a combined temozolomide/bevacizumab and irradiation therapy, as part of a standard care administered by the treating physician team.ConclusionTo our knowledge this is the first published case of a combined cerebellar exophytic glioblastoma with a subsequent solid spinal manifestation. Furthermore this case demonstrates a benefit undergoing this special adjuvant therapy regime in terms of overall survival. Due to the limited overall prognosis of the disease, spinal manifestations of glioma are rarely clinically relevant. The results of our instructive case, however, with a positive effect on both life quality and survival warrant treating future patients in the frame of a prospective clinical study.

Primary central nervous system lymphoma and meningioma in DOTATATE PET/CT.

Although meningiomas are among the most frequent intracranial tumors, primary central nervous system lymphoma represents a rare variant of extranodal non-Hodgkin-type lymphoma. Here, we report on a 73-year-old man with 2 suspicious intracerebral lesions. Combined DOTATATE PET/CT identified 1 lesion as meningioma, whereas the second lesion could not be further specified although a different meningioma was felt very unlikely. Open biopsy of this lesion confirmed the diagnosis of primary central nervous system lymphoma.

High-Efficiency Transfection of Glioblastoma Cells and a Simple Spheroid Migration Assay

Despite international research efforts, patients with glioblastoma multiforme (GBM)-the most common malignant brain tumors in adults-exhibit a very unfavorable prognosis. Their aggressive local growth pattern and increased invasiveness, due to a high motility of the tumor cells, hamper treatment. However, the molecular mechanisms regulating glioblastoma cell migration are still elusive. Here, we describe the combination of a highly efficient cell transfection by Nucleofection® technology and the generation of spheroids from these transfected glioblastoma cell lines. Nucleofection allows the manipulation of protein expression by overexpression and siRNA mediated protein knockdown. Transfection efficiencies >70% can be achieved with some GBM cell lines. Transfected neurospheres then can be used for migration assays (as described here in detail) and a multitude of other functional assays. In comparison to monolayer cultures, the advantage of spheroids is their resemblance with organized tissue in combination with the accuracy of in vitro methodology and marked experimental flexibility.