Noninvasive differentiation of meningiomas from other brain tumours using combined 111Indium-octreotide/99mtechnetium-DTPA brain scintigraphy

Somatostatin and Somatostatin Receptors in Tumour Biology

Somatostatin (SST), a growth hormone inhibitory peptide, is expressed in endocrine and non-endocrine tissues, immune cells and the central nervous system (CNS). Post-release from secretory or immune cells, the first most appreciated role that SST exhibits is the antiproliferative effect in target tissue that served as a potential therapeutic intervention in various tumours of different origins. The SST-mediated in vivo and/or in vitro antiproliferative effect in the tumour is considered direct via activation of five different somatostatin receptor subtypes (SSTR1-5), which are well expressed in most tumours and often more than one receptor in a single cell. Second, the indirect effect is associated with the regulation of growth factors. SSTR subtypes are crucial in tumour diagnosis and prognosis. In this review, with the recent development of new SST analogues and receptor-specific agonists with emerging functional consequences of signaling pathways are promising therapeutic avenues in tumours of different origins that are discussed.

The Stroke-Induced Blood-Brain Barrier Disruption: Current Progress of Inspection Technique, Mechanism, and Therapeutic Target

Stroke is one of the leading causes of mortality and morbidity worldwide. The blood-brain barrier (BBB) is a characteristic structure of microvessel within the brain. Under normal physiological conditions, the BBB plays a role in the prevention of harmful substances entering into the brain parenchyma within the central nervous system. However, stroke stimuli induce the breakdown of BBB leading to the influx of cytotoxic substances, vasogenic brain edema, and hemorrhagic transformation. Therefore, BBB disruption is a major complication, which needs to be addressed in order to improve clinical outcomes in stroke. In this review, we first discuss the structure and function of the BBB. Next, we discuss the progress of the techniques utilized to study BBB breakdown in in-vitro and in-vivo studies, along with biomarkers and imaging techniques in clinical settings. Lastly, we highlight the mechanisms of stroke-induced neuroinflammation and apoptotic process of endothelial cells causing BBB breakdown, and the potential therapeutic targets to protect BBB integrity after stroke. Secondary products arising from stroke-induced tissue damage provide transformation of myeloid cells such as microglia and macrophages to pro-inflammatory phenotype followed by further BBB disruption via neuroinflammation and apoptosis of endothelial cells. In contrast, these myeloid cells are also polarized to anti-inflammatory phenotype, repairing compromised BBB. Therefore, therapeutic strategies to induce anti-inflammatory phenotypes of the myeloid cells may protect BBB in order to improve clinical outcomes of stroke patients.

The Role of Somatostatin in Vasogenic Meningioma Associated Brain Edema

Many tumors, including meningiomas, express somatostatin receptors, suggesting the application of somatostatin analogues for therapy and diagnosis. Sixty percent of meningiomas are associated with perilesional edema, whose development seems to be related to the vascular endothelial growth factor, although it requires an efficient pial blood supply. However, in several neoplastic models, other mediators seem to cooperate with vascular endothelial growth factor in regulating angiogenesis. We evaluated somatostatin receptors (sst2) in relation to the possibility that somatostatin analogues may influence vascular endothelial growth factor production with reduction of edema. Of 35 studied meningiomas, 21 presented peritumoural edema. Vascular endothelial growth factor, microvascular density and pial blood supply were significantly related to the edema (P = 0.0001, P = 0.0001, P = 0.0005). Similarly, a relation was found between sst2 and microvascular density (r = 0.58, P <0.001) and between sst2 and vascular endothelial growth factor expression (P = 0.03). This suggests that somatostatin analogues may be relevant for the treatment of meningiomas.

SPECT-DTPA as a tool for evaluating the blood-brain barrier in post-stroke seizures

Stroke is a well-known cause for seizures in the adult population. Research in animal models indicates that abnormalities in the blood-brain barrier (BBB) permeability can play a role in the development of spontaneous seizures or status epilepticus. The integrity of the BBB was investigated in patients with late post-stroke seizures by performing DTPA-SPECT studies to evaluate the correlation of BBB dysfunction in late post-stroke seizures. All patients with late-onset post-cortical stroke seizures hospitalized during 2009-2010 underwent a brain DTPA-SPECT within 72 h of the first seizure and were compared to a control group of stroke patients without seizures. Twenty-eight patients were included in the study. Twelve out of 14 (85.7%) in the group of seizure post-stroke patients had a positive brain DTPA-SPECT showing disruption of the BBB in the region of the stroke respective to four patients out of 14 (28.6%) in the control group of stroke patients without seizures (p = 0.001). The results of this study suggest that there is a correlation between late post-stroke seizures and BBB disruption, as revealed by DTPA-SPECT examination. Perhaps, this finding could lead to the hypothesis that the BBB disruption can predict developing seizures in patients with cortical stroke.

Synthesis and evaluation of amino acid-based radiotracer 99mTc-N4-AMT for breast cancer imaging

Purpose. This study was to develop an efficient synthesis of ^99mTc-O-[3-(1,4,8,11-tetraazabicyclohexadecane)-propyl]-α-methyl tyrosine (^99mTc-N4-AMT) and evaluate its potential in cancer imaging. Methods. N4-AMT was synthesized by reacting N4-oxalate and 3-bromopropyl AMT (N-BOC, ethyl ester). In vitro cellular uptake kinetics of ^99mTc-N4-AMT was assessed in rat mammary tumor cells. Tissue distribution of the radiotracer was determined in normal rats at 0.5–4 h, while planar imaging was performed in mammary tumor-bearing rats at 30–120 min. Results. The total synthesis yield of N4-AMT was 14%. Cellular uptake of ^99mTc-N4-AMT was significantly higher than that of ^99mTc-N4. Planar imaging revealed that ^99mTc-N4-AMT rendered greater tumor/muscle ratios than ^99mTc-N4. Conclusions. N4-AMT could be synthesized with a considerably high yield. Our in vitro and in vivo data suggest that ^99mTc-N4-AMT, a novel amino acid-based radiotracer, efficiently enters breast cancer cells, effectively distinguishes mammary tumors from normal tissues, and thus holds the promise for breast cancer imaging.

[68Ga]-DOTATOC-PET/CT for meningioma IMRT treatment planning

Purpose

The observation that human meningioma cells strongly express somatostatin receptor (SSTR 2) was the rationale to analyze retrospectively in how far DOTATOC PET/CT is helpful to improve target volume delineation for intensity modulated radiotherapy (IMRT).

Patients and Methods

In 26 consecutive patients with preferentially skull base meningioma, diagnostic magnetic resonance imaging (MRI) and planning-computed tomography (CT) was complemented with data from [⁶⁸Ga]-DOTA-D Phe¹-Tyr³-Octreotide (DOTATOC)-PET/CT. Image fusion of PET/CT, diagnostic computed tomography, MRI and radiotherapy planning CT as well as target volume delineation was performed with OTP-Masterplan^®. Initial gross tumor volume (GTV) definition was based on MRI data only and was secondarily complemented with DOTATOC-PET information. Irradiation was performed as EUD based IMRT, using the Hyperion Software package.

Results

The integration of the DOTATOC data led to additional information concerning tumor extension in 17 of 26 patients (65%). There were major changes of the clinical target volume (CTV) which modify the PTV in 14 patients, minor changes were realized in 3 patients. Overall the GTV-MRI/CT was larger than the GTV-PET in 10 patients (38%), smaller in 13 patients (50%) and almost the same in 3 patients (12%). Most of the adaptations were performed in close vicinity to bony skull base structures or after complex surgery. Median GTV based on MRI was 18.1 cc, based on PET 25.3 cc and subsequently the CTV was 37.4 cc. Radiation planning and treatment of the DOTATOC-adapted volumes was feasible.

Conclusion

DOTATOC-PET/CT information may strongly complement patho-anatomical data from MRI and CT in cases with complex meningioma and is thus helpful for improved target volume delineation especially for skull base manifestations and recurrent disease after surgery.

The role of 111indium-octreotide brain scintigraphy in the diagnosis of cranial, dural-based meningiomas

OBJECTIVE

Meningiomas are common brain tumors with somatostatin receptors that bind octreotide. We report the use of (111)indium-octreotide brain scintigraphy (OBS) for the non-invasive differentiation of meningiomas from other cranial dural-based pathology.

METHODS

A retrospective analysis of our experience with OBS for non-invasive identification of meningiomas was performed. Two neuroradiologists, blinded to clinical data, utilized a standardized grading scheme to define the uptake of octreotide at 6 and 24 h post-administration. The correlation between (18) F-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET), magnetic resonance imaging (MRI) scans, and octreotide uptake was assessed.

RESULTS

The cohort consisted of 50 patients having a mean age of 62.4 years and a median follow-up time of 24 months. Management consisted of biopsy (n = 4); resection (n = 10); observation (n = 16); radiosurgery (n = 21); and external beam radiotherapy (n = 3). OBS was correlated with MRI (n = 50); FDG-PET brain studies (n = 38); histology (n = 14), and angiography (n = 1). In cases where definitive diagnosis could be made, the sensitivity, specificity, positive and negative predictor values for OBS alone were 100; 50; 75; and 100, respectively. OBS provided false positive data in 3 patients (metastasis, chronic inflammation, lymphoma). Use of OBS with MRI to differentiate meningiomas from other lesions was highly significant (P < 0.001). FDG-PET correctly identified malignant pathology with 100% sensitivity and specificity.

CONCLUSION

OBS may increase the diagnostic specificity of conventional MRI when differentiating meningioma from other dural-based pathologies, while the addition of FDG-PET differentiates benign from malignant lesions.

Prognostic Significance of Blood Brain Barrier Permeability in Acute Hemorrhagic Stroke

BACKGROUND

Blood brain barrier (BBB) disruption is accompanied by edema in the surrounding areas of the intracerebral hemorrhage (ICH). The aim of the study was to clarify the correlation between BBB breakdown and outcome in ICH.

PATIENTS

Twenty-seven patients with primary ICH were included in the study. Each patient underwent CT and DTPA-SPECT, and the National Institutes of Health (NIH) and modified Rankin score were performed as well.

RESULTS

DTPA-SPECT had a significant correlation with the modified Rankin score after 3 months (p = 0.008) and 6 months (p = 0.01). The CT scan was directly correlated with the NIH score on days 1, 7 and 30 (p = 0.01, p = 0.01 and p = 0.04, respectively). No correlation was found between DTPA-SPECT and CT scan data.

CONCLUSIONS

The degree of BBB breakdown, as imaged by the DTPA-SPECT technique, was directly correlated with the late functional outcome. The CT scan has an inverse correlation with the NIH score. These findings may have broad clinical implications.

Receptor-Mediated Tumor Targeting with Radiopeptides. Part 1. General Concepts and Methods: Applications to Somatostatin Receptor-Expressing Tumors

Radiolabeled peptides have become important tools in nuclear oncology, both as diagnostics and more recently also as therapeutics. They represent a distinct sector of the molecular targeting approach, which in many areas of therapy will implement the old "magic bullet" concept by specifically directing the therapeutic agent to the site of action. In this three-part review, we present a comprehensive overview of the literature on receptor-mediated tumor targeting with the different radiopeptides currently studied. Part I summarizes the general concepts and methods of targeting, the selection of radioisotopes, chelators, and the criteria of peptide ligand development. Then, the >400 studies on the application to somatostatin/somatostatin-release inhibiting factor receptor-mediated tumor localization and treatment will be reviewed, demonstrating that peptide radiopharmaceuticals have gained an important position in clinical medicine.

Craniofacial hemangiopericytoma associated with oncogenic osteomalacia: case report

A craniofacial hemangiopericytoma associated with oncogenic osteomalacia is described and the literature is reviewed. A 46 year-old male with multiple fractures and hypophosphatemia was found to have a craniofacial mass extending from the right ethmoid sinus into the right frontal lobe. Initial detection of the tumor was made with an 111Indium-pentreotide scan (Octreoscan). Gross total resection of the tumor was achieved and the patient received postoperative radiation therapy. One year after surgery, the patient remains free of tumor with significant increase in bone density and normal phosphate levels. This is the first report of a hemangiopericytoma invading the brain that was associated with paraneoplastic hypophosphatemia and osteomalacia. Also, this is the first reported detection of a hemangiopericytoma by an Octreoscan. Primary detection and secondary surveillance of hemangiopericytomas may be possible with serial Octreoscans.