18F-Fluorodeoxyglucose PET/Computed Tomography for Primary Brain Tumors

MRI Characteristics of Primary Brain Tumors and Advanced Diagnostic Imaging Techniques

Extensive descriptions of MRI characteristics of canine and feline brain tumors allow for relatively accurate lesion detection, discrimination, and presumptive diagnosis on MRI. Ambiguous and overlapping MRI features between brain lesion and tumor as well as tumor types is a limitation that necessitates histopathology for final diagnosis, which is often not available antemortem. Non-invasive advanced diagnostic imaging techniques continue to be developed to enhance sensitivity and specificity for brain tumor diagnosis on MRI in dogs and cats.

Porphyrin-Based Brain Tumor-Targeting Agents: [64Cu]Cu-porphyrin and [64Cu]Cu-TDAP

The aim of this study is to evaluate a radioactive metal complex platform for brain tumor targeting. Herein, we introduce a new porphyrin derivative, 5,10,15,20-(tetra-N,N-dimethyl-4-aminophenyl)porphyrin (TDAP), in which four N,N-dimethyl-4-p-phenylenediamine (DMPD) moieties are conjugated to the porphyrin labeled with the radiometal 64Cu. DMPD affected the pharmacokinetics of porphyrin in terms of retention time in vivo and tumor-targeting ability relative to those of unmodified porphyrin. [64Cu]Cu-TDAP showed stronger enhancement than [64Cu]Cu-porphyrin in U87MG glioblastoma cells, especially in the cytoplasm and nucleus, indicating its tumor-targeting properties and potential use as a therapeutic agent. In the subcutaneous and orthotopic models of brain-tumor-bearing mice, [64Cu]Cu-TDAP was clearly visualized in the tumor site via positron emission tomography imaging and showed a tumor-to-brain ratio as high as 13. [64Cu]Cu-TDAP deserves attention as a new diagnostic agent that is suitable for the early diagnosis and treatment of brain tumors.

Pineal gland hypermetabolic involvement without central nervous system symptoms in a pediatric patient with primary nodular sclerosis subtype classical Hodgkin Lymphoma

This case report presents the first reported pediatric case of primary classical nodular sclerosing Hodgkin Lymphoma (HL) with pineal gland involvement, presenting without CNS symptoms, which completely resolved after 2 cycles of chemotherapy. The 12 year-old male first presented with a right inguinal mass and external iliac lymphadenopathy accompanied by B symptoms. He was diagnosed with stage IV B classical HL, and as part of the staging work-up, a full-body PET/CT scan was performed. In addition to the right inguinal mass, the PET/CT demonstrated increased FDG uptake at the pineal gland along with level II lymph nodes. The patient was treated with ABVE-PC chemotherapy (Doxorubicin, Bleomycin, Vincristine, Etoposide, Prednisone, and Cyclophosphamide) as per standard arm of AHOD1331 COG protocol for newly diagnosed high-risk HL patients, which resolved the pineal mass after 2 cycles without requiring radiation therapy. Following 5 cycles, a full-body PET/CT showed no brain or neck activity, along with decreased size and activity of the right groin mass. To our knowledge, there are no other documented cases of primary HL with specific pineal involvement, and no cases that lack CNS symptoms altogether like this one did. Additionally, this is the third published pediatric case of primary CNS-HL, both of the previous cases were treated with radiotherapy and presented with CNS symptoms. Thus, this case demonstrates the importance of ordering a full-body PET/CT as part of the initial HL work-up and provides evidence that chemotherapy alone is a treatment option for some patients with primary intracranial HL.

Organ Donation and Primary Central Nervous System Tumors

Primary central nervous system tumors can be the cause of brain death. Not all of them contraindicate the donation of organs and tissues for transplant. A survey of cases was carried out in our country in which it was observed that the number of brain deaths caused by primary tumors was low, of the order of 2%, with an ẋ (media) of 3 by year, which would increase the potential for donation. Medical records, an anatomopathologic study, and a detailed physical examination will be fundamental when applying the donor selection criteria. Nuclear magnetic resonance in expert hands has a sensitivity of 96% to catalog the benignity or malignancy of this type of tumors.

2-[18F]FELP, a novel LAT1-specific PET tracer, for the discrimination between glioblastoma, radiation necrosis and inflammation

INTRODUCTION

Considering the need for rapid change of treatment in recurrent glioblastoma (GB), it is of utmost importance to characterize PET radiopharmaceuticals that allow early discrimination of tumor from therapy-related effects. In this study, we examined the value of 2-[¹⁸F]FELP as a LAT1 tumor-specific PET tracer in comparison with [¹⁸F]FDG and [¹⁸F]FET in a combined orthotopic rat radiation necrosis and glioblastoma model. A second experiment compared 2-[¹⁸F]FELP to [¹⁸F]FDG in a mouse glioblastoma - inflammation model.

METHODS

Using the small animal radiation research platform (SARRP), radiation necrosis (RN) was induced in the left frontal lobe of the rat brain. When radiation-induced changes were visible on MRI, F98 rat glioblastoma cells were stereotactically inoculated in the contralateral right frontal lobe. When tumor growth was confirmed on MRI, 2-[¹⁸F]FELP, [¹⁸F]FET and [¹⁸F]FDG PET scans were acquired on three consecutive days. In an inflammation experiment, mice were inoculated in the left thigh with U87 human glioblastoma cells. After heterotopic tumor growth was confirmed macroscopically, inflammation was induced by injection of turpentine subcutaneously in the right thigh. Subsequently, 2-[¹⁸F]FELP and [¹⁸F]FDG scans were acquired on two consecutive days.

RESULTS

The in vivo PET images demonstrated that 2-[¹⁸F]FELP could differentiate glioblastoma and radiation necrosis using SUV_mean (p = 0.0016) and LNR_mean (p = 0.009), while [¹⁸F]FET was only able to differentiate both lesions by means of the SUV_mean. (p = 0.047) Delayed [¹⁸F]FDG_late PET (4 h postinjection) was also able to distinguish glioblastoma from radiation necrosis, but smaller lesion-to-normal brain ratios were observed (SUV_mean: p = 0.009; LNR_mean: p = 0.028). In the inflammation study, 2-[¹⁸F]FELP showed no significant uptake in the inflammation lesion when compared to the control group (SUVmean: p = 0.149; LNRmean: p = 0.083). In contrast, both conventional and delayed [¹⁸F]FDG displayed significant uptake in the turpentine-invoked lesion (SUVmean: p = 0.021; LNRmean: p = 0.021).

CONCLUSION

This study suggests that the 2-[¹⁸F]FELP PET is able to differentiate glioblastoma from radiation necrosis and that the 2-[¹⁸F]FELP uptake is less likely to be contaminated by the presence of inflammation than the [¹⁸F]FDG signal.

ADVANCES IN KNOWLEDGE

These results are clinically relevant for the differential diagnosis between tumor and radiation necrosis because radiation necrosis always contains a certain amount of inflammatory cells. Hence, 2-[¹⁸F]FELP is preferred to discriminate tumor from radiation necrosis.

The Molecular Effects of Ionizing Radiations on Brain Cells: Radiation Necrosis vs. Tumor Recurrence

The central nervous system (CNS) is generally resistant to the effects of radiation, but higher doses, such as those related to radiation therapy, can cause both acute and long-term brain damage. The most important results is a decline in cognitive function that follows, in most cases, cerebral radionecrosis. The essence of radio-induced brain damage is multifactorial, being linked to total administered dose, dose per fraction, tumor volume, duration of irradiation and dependent on complex interactions between multiple brain cell types. Cognitive impairment has been described following brain radiotherapy, but the mechanisms leading to this adverse event remain mostly unknown. In the event of a brain tumor, on follow-up radiological imaging often cannot clearly distinguish between recurrence and necrosis, while, especially in patients that underwent radiation therapy (RT) post-surgery, positron emission tomography (PET) functional imaging, is able to differentiate tumors from reactive phenomena. More recently, efforts have been done to combine both morphological and functional data in a single exam and acquisition thanks to the co-registration of PET/MRI. The future of PET imaging to differentiate between radionecrosis and tumor recurrence could be represented by a third-generation PET tracer already used to reveal the spatial extent of brain inflammation. The aim of the following review is to analyze the effect of ionizing radiations on CNS with specific regard to effect of radiotherapy, focusing the attention on the mechanism underling the radionecrosis and the brain damage, and show the role of nuclear medicine techniques to distinguish necrosis from recurrence and to early detect of cognitive decline after treatment.

Clinical value of 18F-FDG-PET/CT in suspected serious disease with special emphasis on occult cancer

PURPOSE

Suspected serious disease (SSD) is a disease designation often given to patients with one or more non-specific symptoms of severe disease that could be due to cancer; the optimal diagnostic strategy is largely left to the clinician's discretion. Being a sensitive non-invasive whole-body imaging modality ¹⁸F-FDG-PET/CT may have a potential role in this cancer-prevalent group of patients to confirm or refute suspected malignancy. We aimed to investigate the diagnostic value of ¹⁸F-FDG-PET/CT in SSD using long-term follow-up as reference.

METHODS

We retrospectively studied results obtained in all SSD patients referred for ¹⁸F-FDG-PET/CT at a single institution in 2010-2011 retrieving the following clinical data in all patients: journal entries, examinations, and evaluations made from 6 months before the scan and until the latest recorded entry. A true positive PET scan was a positive scan with a subsequently biopsy-confirmed diagnosis of cancer in the same target organ, whereas a false positive scan had no subsequent cancer diagnosis. A true negative PET scan was a negative scan without a cancer diagnosis during follow-up, whereas a false negative PET scan was one with a subsequently confirmed cancer diagnosis.

RESULTS

Ninety-three patients, aged 67 years (range 25-89) were included and followed for up to 7.3 years (median 6). Of these, 21 [22.6% (95% CI 15.3-32.1)] turned out to have cancer. With ¹⁸F-FDG-PET/CT, the sensitivity was 81.0% (95% CI 60.0-92.3), specificity 76.4% (95% CI 65.4-84.7), positive predictive value 50% (95% CI 34.1-65.9), and negative predictive value 93.2% (95% CI 83.8-97.3). Five patients with negative scans were subsequently diagnosed with cancer.

CONCLUSION

Cancer prevalence is substantial among patients with SSD. ¹⁸F-FDG-PET/CT is a promising option in this setting, in particular because a high negative predictive value equals a low incidence of cancer during follow-up. Further studies are needed to establish the role of ¹⁸F-FDG-PET/CT in SSD.

Comparisons of the accuracy of radiation diagnostic modalities in brain tumor: A nonrandomized, nonexperimental, cross-sectional trial

Tumor morphology improved sensitivity, accuracy, and specificity of the diagnosis, but all diagnostic techniques have attenuation correction issues.To compare computed tomographic (CT), positron emission tomographic (PET), and magnetic resonance imaging (MRI) characteristics of patients with brain tumor in a Chinese setting.A nonrandomized, nonexperimental, cross-sectional trial.Jining No. 1 People's Hospital, China.In total, 127 patients who had clinically confirmed a brain tumor were included in the cross-sectional study. Patients were subjected to brain CT, MRI, and PET. The tumors resected after brain surgery were subjected to morphological diagnosis. Statistical analysis of data of surgically removed tumor and that of different methods of diagnosis was performed using Wilcoxon test following Tukey-Kramer test. Spearmen correlation was performed between diagnostic modalities and in vivo morphology. Results were considered significant at 99% of confidence level.The data of diameter and volume of tumor derived from CT (Spearman r = 0.9845 and 0.9706), and MRI (Spearman r = 0.955 and 0.2378) were failed to correlate with that of that of the surgically removed tumor. However, prediction of diameter and volume of the tumor by PET (Spearman r = 0.9922 and 0.9921) were correlated with that of the surgically removed tumor. CT and MRI were failed to quantified pituitary adenomas.The study was recommended PET for assessment of brain tumor.

Current Radiopharmaceuticals for Positron Emission Tomography of Brain Tumors

Brain tumors represent a diverse spectrum of histology, biology, prognosis, and treatment options. Although MRI remains the gold standard for morphological tumor characterization, positron emission tomography (PET) can play a critical role in evaluating disease status. This article focuses on the use of PET with radiolabeled glucose and amino acid analogs to aid in the diagnosis of tumors and differentiate between recurrent tumors and radiation necrosis. The most widely used tracer is ¹⁸F-fluorodeoxyglucose (FDG). Although the intensity of FDG uptake is clearly associated with tumor grade, the exact role of FDG PET imaging remains debatable. Additionally, high uptake of FDG in normal grey matter limits its use in some low-grade tumors that may not be visualized. Because of their potential to overcome the limitation of FDG PET of brain tumors, ¹¹C-methionine and ¹⁸F-3,4-dihydroxyphenylalanine (FDOPA) have been proposed. Low accumulation of amino acid tracers in normal brains allows the detection of low-grade gliomas and facilitates more precise tumor delineation. These amino acid tracers have higher sensitivity and specificity for detecting brain tumors and differentiating recurrent tumors from post-therapeutic changes. FDG and amino acid tracers may be complementary, and both may be required for assessment of an individual patient. Additional tracers for brain tumor imaging are currently under development. Combinations of different tracers might provide more in-depth information about tumor characteristics, and current limitations may thus be overcome in the near future. PET with various tracers including FDG, ¹¹C-methionine, and FDOPA has improved the management of patients with brain tumors. To evaluate the exact value of PET, however, additional prospective large sample studies are needed.