Low-grade Diffuse Astrocytomas Research Articles

Genomic characterization of IDH-mutant astrocytoma progression to grade 4 in the treatment setting

As the progression of low-grade diffuse astrocytomas into grade 4 tumors significantly impacts patient prognosis, a better understanding of this process is of paramount importance for improved patient care. In this project, we analyzed matched IDH-mutant astrocytomas before and after progression to grade 4 from six patients (discovery cohort) with genome-wide sequencing, 21 additional patients with targeted sequencing, and 33 patients from Glioma Longitudinal AnalySiS cohort for validation. The Cancer Genome Atlas data from 595 diffuse gliomas provided supportive information. All patients in our discovery cohort received radiation, all but one underwent chemotherapy, and no patient received temozolomide (TMZ) before progression to grade 4 disease. One case in the discovery cohort exhibited a hypermutation signature associated with the inactivation of the MSH2 and DNMT3A genes. In other patients, the number of chromosomal rearrangements and deletions increased in grade 4 tumors. The cell cycle checkpoint gene CDKN2A, or less frequently RB1, was most commonly inactivated after receiving both chemo- and radiotherapy when compared to other treatment groups. Concomitant activating PDGFRA/MET alterations were detected in tumors that acquired a homozygous CDKN2A deletion. NRG3 gene was significantly downregulated and recurrently altered in progressed tumors. Its decreased expression was associated with poorer overall survival in both univariate and multivariate analysis. We also detected progression-related alterations in RAD51B and other DNA repair pathway genes associated with the promotion of error-prone DNA repair, potentially facilitating tumor progression. In our retrospective analysis of patient treatment and survival timelines (n = 75), the combination of postoperative radiation and chemotherapy (mainly TMZ) outperformed radiation, especially in the grade 3 tumor cohort, in which it was typically given after primary surgery. Our results provide further insight into the contribution of treatment and genetic alterations in cell cycle, growth factor signaling, and DNA repair-related genes to tumor evolution and progression.

P10.14.B PROGRESSION OF IDH-MUTANT ASTROCYTOMAS TO GRADE 4 UNDER TREATMENT-RELATED SELECTION PRESSURE

Abstract BACKGROUND The progression of low-grade diffuse astrocytomas into grade 4 tumors significantly impacts patient prognosis, therefore a better understanding of this process is of paramount importance for improved patient care. MATERIAL AND METHODS We analyzed next-generation sequencing data from matched IDH-mutant astrocytomas before and after progression to grade 4 from up to 27 patients as well as publicly available The Cancer Genome Atlas (TCGA) data from up to 595 cases. All patients in our discovery cohort with genome-wide sequencing data received radiation, all but one underwent chemotherapy, and no patient received temozolomide before progression to grade 4. RESULTS One case in the discovery cohort exhibited a hypermutation signature associated with inactivation of the MSH2 and DNMT3A genes. In other patients, the number of novel chromosomal rearrangements and deletions increased in grade 4 tumors. Tumor progression was associated with upregulated cell cycle progression, migration, and DNA damage repair-related genes. Upon progression, the cell cycle checkpoint genes CDKN2A or RB1 were most commonly inactivated, especially after postoperative radiation and chemotherapy, followed by activating growth factor receptor gene alterations in cases with homozygous CDKN2A deletion. We also detected alterations in DNA repair pathway genes associated with therapy resistance and the promotion of error-prone DNA repair, thus facilitating tumor progression. The homologous recombination repair gene RAD51B was hemizygously deleted in all but one progressed tumor in our discovery cohort. In our retrospective nonrandomized survival analysis, treatment including both radio- and chemotherapy improved relapse-free and overall survival compared to other treatments in cases with primary grade 3 diagnosis. Similar benefit was not observed for cases with primary grade 2 diagnosis, and radiation as sole postoperative treatment was not significantly improving the prognosis in any of the analyses. CONCLUSION Our results support the previous notions that treatment-induced DNA damage can contribute to tumor progression to grade 4 and suggest that altered DNA repair has a role in treatment resistance and tumor progression.

EPCO-11. GATEKEEPER INACTIVATION DRIVES TUMOR PROGRESSION TO GRADE IV ASTROCYTOMA

Abstract IDH-mutant low-grade diffuse astrocytomas frequently progress to grade IV astrocytomas with implications for patient prognosis. To better understand this process, we applied whole-genome and transcriptome sequencing to matched tumor samples collected before and after progression to grade IV astrocytomas from five patients. All tumors carried an IDH1 mutation. The number of chromosomal rearrangements was increased between 1.3 and 3.5-fold in the tumors upon progression, with the exception of one case, in which the increase was only 1.03-fold. This case exhibited a hypermutation signature caused by homozygous deletion of the MSH2 gene, which encodes a member of the DNA mismatch repair complex. The most common genomic alterations acquired at progression were homozygous deletions in the CDKN2A/ RB1 -pathway or hemizygous deletion of PTEN. Additionally, PDGFRA was amplified in two grade IV tumors, with concordantly increased expression. For one of these cases, a PDGFRA-amplified subclone is likely to be present already in the low-grade astrocytoma. We further detected intrachromosomal rearrangements closeby the genes NRG3 in the progressed tumors as well as in the The Cancer Genome Atlas (TCGA) cohort. The expression of NRG3 decreased with increasing grade in the TCGA cohort and the gene was frequently deleted. Lower NRG3 expression was associated with shorter survival in the TCGA cohort. Several miRNAs showed differential expression upon progression. For two miRNAs the predicted targets were associated with cell cycle regulation and we detected inverse correlation between miRNA and target mRNA expression. While progression seems to occur via different pathways, the predicted outcome for many of the alterations was the inactivation of tumor suppressor genes and further dysregulation of cell proliferation.

An MRI-based joint model of radiomics and spatial distribution differentiates autoimmune encephalitis from low-grade diffuse astrocytoma

The differential diagnosis between autoimmune encephalitis and low-grade diffuse astrocytoma remains challenging. We aim to develop a quantitative model integrating radiomics and spatial distribution features derived from MRI for discriminating these two conditions. In our study, we included 188 patients with confirmed autoimmune encephalitis (n = 81) and WHO grade II diffuse astrocytoma (n = 107). Patients with autoimmune encephalitis (AE, n = 59) and WHO grade II diffuse astrocytoma (AS, n = 79) were divided into training and test sets, using stratified sampling according to MRI scanners. We further included an independent validation set (22 patients with AE and 28 patients with AS). Hyperintensity fluid-attenuated inversion recovery (FLAIR) lesions were segmented for each subject. Ten radiomics and eight spatial distribution features were selected via the least absolute shrinkage and selection operator (LASSO), and joint models were constructed by logistic regression for disease classification. Model performance was measured in the test set using the area under the receiver operating characteristic (ROC) curve (AUC). The discrimination performance of the joint model was compared with neuroradiologists. The joint model achieved better performance (AUC 0.957/0.908, accuracy 0.914/0.840 for test and independent validation sets, respectively) than the radiomics and spatial distribution models. The joint model achieved lower performance than a senior neuroradiologist (AUC 0.917/0.875) but higher performance than a junior neuroradiologist (AUC 0.692/0.745) in the test and independent validation sets. The joint model of radiomics and spatial distribution from a single FLAIR could effectively classify AE and AS, providing clinical decision support for the differential diagnosis between the two conditions.

Double dose of 5-aminolevulinic acid and its effect on protoporphyrin IX accumulation in low-grade glioma.

Administration of 5-aminolevulinic acid (5-ALA) does not regularly elicit fluorescence in low-grade glioma (LGG) at currently established doses and timing of administration. One explanation may be differences in blood-brain barrier (BBB) integrity compared to high-grade glioma. The authors hypothesized that for a BBB semipermeable to 5-ALA there might be a relationship between plasma 5-ALA concentration and its movement into the brain. A higher dose would elicit more 5-ALA conversion into protoporphyrin IX (PPIX). The authors present a case series of patients harboring LGG who received higher doses of 5-ALA. Patients undergoing surgery for indeterminate glioma later diagnosed as LGG were included in this study. 5-ALA was administered at a standard dose of 20 mg/kg body weight (bw) 4 hours prior to induction of anesthesia. A subgroup of patients received a higher dose of 40 mg/kg bw. Fluorescence was evaluated visually and PPIX concentration (cPPIX) was determined ex vivo by hyperspectral measurements in freshly extracted tissue. All adverse events were recorded. A total of 23 patients harboring diffuse low-grade astrocytomas (n = 19) and oligodendrogliomas (n = 4) were analyzed. Thirteen patients received 20 mg/kg bw, and 10 patients received 40 mg/kg bw of 5-ALA. In the 20 mg/kg group, 30.8% (4 of 13) of tumors harbored areas of visible fluorescence, compared to 60% of cases (n = 6 of 10) with 40 mg/kg bw. The threshold to visibility was 1 μg/ml in both groups. Measured over all biopsies, the mean cPPIX was significantly higher in the double-dose group (1.8 vs 0.45 μg/ml; p < 0.001). In non-visibly fluorescent tissue the mean cPPIX was 0.146 μg/ml in the 20 mg/kg and 0.347 μg/ml in the 40 mg/kg group, indicating an increase of 138% (p < 0.001). These observations demonstrate different regions with different levels of PPIX accumulation in LGG. With higher 5-ALA doses cPPIX increases, leading to more regions surpassing the visibility threshold of 1 μg/ml. These observations can be explained by the fact that the BBB in LGG is semipermeable to 5-ALA. Higher 5-ALA doses result in more PPIX conversion, an observation with implications for future dosing in LGG.

HGG-38. Gliomatosis cerebri/Glioblastoma with discordant histological and molecular profiles - treatment and outcome of a pediatric patient

Gliomatosis cerebri is no longer recognized as a distinctive pathological diagnosis, but a manifestation of diffuse glioma involving at least three cerebral lobes. Lack of understanding in this manifestation of CNS neoplasms limits treatment for this aggressive disease. Here we present a case of stabilization of disease in a pediatric patient with unusual molecular profiles normally associated with aggressive tumor behavior. A nine-year-old male presented with acute onset of right-sided vision changes, headache and numbness of the left arm and leg for one day. He also had a three-month history of an asymptomatic bump on the right temporal skull bone. MRI of the brain was significant for diffuse thickening of the cortex of the entire right hemisphere (temporal>frontal>parietal lobes). No specific enhancing lesion or restricted diffusion was noted. Histologically, the tissue had findings of diffuse low-grade astrocytoma. Molecular genetic testing was notable for TERT and EGFR mutations which are more consistent with adult type high-grade astrocytic tumors. MGMT promoter methylation array was negative. Final diagnosis was glioblastoma, IDH and H3 wildtype. All the molecular features of this tumor were high-grade with an average progression free survival of less than 12 months. Despite the lack of methylation, we opted to include alkylating agents in a maintenance chemotherapy treatment plan following radiation therapy with concurrent temozolomide. Despite poor prognostic factors, the patient is alive without signs of progression 2.5 years post-diagnosis. Targeted agents were not used in upfront treatment for this patient. This is a rare case of stabilization of disease with conventional treatment in a very aggressive tumor. This case is a rare constellation of an ‘adult-type’ molecular profile in a pediatric patient with a low grade, less aggressive behavior profile, and highlights the need to better understand this rare subtype of tumors in children.

Application of EGFR, ki 67 and GFAP as a panel for the diagnosis and grading of astrocytomas

Background: Astrocytic tumors are the most common primary central nervous system tumors. WHO grading scheme is based on the presence or absence of the following four histological parameters using haematoxylin and eosin (H&E) staining: cellular atypia (WHO grade II), mitotic figures (WHO grade III), endothelial proliferation, and/or necrosis (WHO grade IV). Immunohistochemistry (IHC) has become an essential tool in diagnosis of brain tumors and helps in predicting the prognosis of certain brain including astrocytomas. Aim: Study the immunohistochemical expressions of (Epidermal growth factor receptor (EGFR), Ki67 and Glial fibrillary acidic protein (GFAP)) in different grades of astrocytomas. Materials and Methods: This study included 44 cases of astrocytomas classified as: 3 pilocytic astrocytomas, 6 diffuse low grade astrocytomas, 15 anaplastic astrocytomas and 20 glioblastoma multiforms. Immunohistochemical staining of all cases using EGFR, Ki67 and GFAP was done. Results: EGFR showed positive membranous and cytoplasmic expression in 33 (75%) cases, GFAP positive staining was detected in 38 (86.4%) of studied cases while all astrocytomas of different grades showed ki67 positivity with variable degrees with the mean ± SEM of Ki67 LI 17.76% ± 2.46. There was statistically significant relation between EGFR, Ki 67 and GFAP expression and tumor grade. Conclusions: EGFR, Ki 67 and GFAP should be used in combination as a panel side by side with established histological criteria of malignancy and WHO grading system for accurate diagnosis and grading of astrocytic tumors.

The Safety and Efficacy of Robot-Assisted Stereotactic Biopsy for Brain Glioma: Earliest Institutional Experiences and Evaluation of Literature

SUMMARYRobot-assisted brain tumor biopsy is becoming one of the most important innovative technologies in neurosurgical practice. The idea behind its engagement is to advance the safety and efficacy of the biopsy procedure, which is much in demand when planning the management of endocranial tumor pathology. Herein, we provide our earliest institutional experiences in utilizing this mesmerizing technology. Cranial robotic device was employed for stereotactic robot-assisted brain glioma biopsy in three consecutive patients from our series: an anaplastic isocitrate dehydrogenase (IDH) negative astrocytoma (WHO grade III) located in the right trigone region of the periventricular white matter; a low grade diffuse astrocytoma (WHO grade II) of bilateral thalamic region spreading into the right mesencephalic area; and an IDH-wildtype glioblastoma (WHO grade IV) of the right frontal lobe producing a contralateral midline shifting. Robot-assisted tumor biopsy was successfully performed to get tissue samples for histopathologic and immunohistochemical analysis. The adjacent tissue iatrogenic damage of the eloquent cortical areas was minimal, while the immediate postoperative recovery was satisfactory in all patients. In conclusion, considering the preliminary results of our early experiences, robot-assisted tumor biopsy was proven to be a feasible and accurate procedure when surgery for brain glioma was not an option. It may increase safety and precision, without expanding surgical time, being similarly effective when compared to standard stereotactic and manual biopsy. Using this method to provide accurate sampling for histopathologic and immunohistochemical analysis is a safe and easy way to determine management strategies and outcome of different types of brain glioma.

A Simple Panel of IDH1 and P53 in Differential Diagnosis Between Low-Grade Astrocytoma and Reactive Gliosis.

Background:Reactive gliosis is a response of glial tissue to different types of injury such as brain abscess, trauma, hemorrhage, or even neoplastic process. In some circumstances, especially when the tissue biopsy is small, there may be difficulty to discriminate this reactive condition with low-grade diffuse astrocytoma (World Health Organization [WHO] grade II) by conventional hematoxylin and eosin (H&E) slides, so some immunohistochemical and molecular markers have been introduced for this differential diagnosis. One of the important aspects of updated WHO classification in 2016 has been dividing some of the glial tumor according to IDH1 (isocitrate dehydrogenase 1) mutation.Objectives:In this study, we tried to evaluate IDH1 and P53 mutation by immunohistochemistry as a simple and highly specific and sensitive method to differentiate low-grade astrocytoma and reactive gliosis.Material and methods:For 5 years (2013-2018), 50 cases of clinically documented reactive gliosis and 50 cases of low-grade astrocytoma were evaluated for the presence or absence of IDH1 and P53 mutation by immunohistochemistry.Results:Isocitrate dehydrogenase 1 was positive in 92% and 4% of the astrocytoma and reactive gliosis cases and P53 was positive in 90% and 4% of the cases with the final diagnosis of astrocytoma and reactive gliosis, respectively.Discussion and conclusion:Combination of P53 and IDH1 as an immunohistochemical panel showed specificity of 96% and sensitivity of 91% for differential diagnosis of reactive gliosis and low-grade astrocytoma. These 2 markers can be extremely helpful for this differential diagnosis.

Profiling of novel circulating microRNAs as a non-invasive biomarker in diagnosis and follow-up of high and low-grade gliomas

ObjectiveGlioblastoma (GBM) is the most common primary malignant neoplasm of the central nervous system (CNS). Despite the progress in therapeutic strategies such as surgical techniques, radiotherapy, chemotherapy, and targeted therapy, prognosis and therapeutically convenient monitoring tools in patients with GBM has not improved significantly up to now.Therefore, exosomal miRNAs as novel non-invasive biomarkers having high sensitivity and specificity are required to improve diagnosis and to develop new targeted therapy strategies for GBM patients. The aim of the present study was to investigate a novel miRNA signature as a predictive biomarker for diagnosis and measurement of response to therapeutic interventions in plasma of GBM patients versus traumatic brain injury and diffuse low-grade astrocytoma (LGA) patients. Patients and methodsPlasma exosomal-microRNAs were isolated from GBM (n = 25), LGA (n = 25), and head trauma patients (n = 15) as non-glioma control from March 2017 to June 2018 in Department of Neurosurgery at Rasoul-e-Akram Hospital. Through a bioinformatics analysis, we used Miranda, TargetScan, mirBase, DIANA-microT-CDS, and KEGG database as well as microarray data analysis from GEO for microRNA candidates. Finally, miR-210, miR-185, miR-5194, and miR-449 were selected among those miRNAs because they were recorded to target the maximum number of genes in EGFR and c-MET signaling pathways. Then, exosomal microRNAs were extracted from plasma of patients and quantitated by locked nucleic acid real-time PCR in GBM, LGA, and trauma patients. ResultsThis result is the first report on the role of circulating miR-185, miR-449, and miR-5194 in GBM compared to LGA and trauma. The plasma expression of miR-210 as an oncogenic miR was upregulated in GBM and LGA groups (P < 0.0001). Otherwise, miR-185, miR-5194, and miR-449 were significantly downregulated (P ≤ 0.05) in GBM and LGA compared to trauma patients. There was no significant downregulation in the expression of miR-185 between GBM and LGA, while the expression of miR-5194 (P ≤ 0.05) and miR-449 (P ≤ 0.05) was significantly decreased in GBM patients compared with LGA. ConclusionsThese results indicate that the levels of miR-210, miR-449, and miR-5194 are a promising diagnostic and prognostic biomarker positively correlated with histopathological grade and invasiveness of GBM. These findings imply that circulating microRNA can be potentially used as novel biomarkers for glioma that might be beneficial in clinical management of glioma patients.

Diffuse Astrocytoma, IDH-Wildtype: A Dissolving Diagnosis.

The histological and molecular features and even the mere existence of diffuse astrocytoma, IDH-wildtype, remain unclear. We therefore examined 212 diffuse astrocytomas (grade II WHO) in adults using IDH1(R132H) immunohistochemistry followed by IDH1/IDH2 sequencing and neuroimaging review. DNA methylation status and copy number profiles were assessed by Infinium HumanMethylation450k BeadChip. Only 25/212 patients harbored tumors without IDH1/IDH2 hotspot mutations and without contrast enhancement. By DNA methylation profiling, 10/25 tumors were classified as glioblastoma, IDH-wildtype, and an additional 7 cases could not be classified using methylome analysis, but showed genetic characteristics of glioblastoma. Histologically, all of these 17 tumors were low-grade diffuse astrocytomas. Nevertheless, 10/17 patients experienced early malignant progression. Other methylation classes included diffuse midline glioma, H3 K27M-mutant, diffuse astrocytoma, IDH-mutant, pilocytic astrocytoma, and normal or reactive brain tissue (total n = 8). In conclusion, no convincing diffuse astrocytoma, IDH-wildtype, was identified. Most IDH-wildtype tumors showing histopathological and radiological features of low-grade diffuse astrocytoma exhibit molecular and clinical features of high-grade glioma and may represent an early stage of primary glioblastoma. Our findings have implications for the biology, classification and neuropathological diagnosis of diffuse astrocytoma, IDH-wildtype in adults.

Microsomal membrane proteome of low grade diffuse astrocytomas: Differentially expressed proteins and candidate surveillance biomarkers

Diffuse astrocytoma (DA; WHO grade II) is a low-grade, primary brain neoplasm with high potential of recurrence as higher grade malignant form. We have analyzed differentially expressed membrane proteins from these tumors, using high-resolution mass spectrometry. A total of 2803 proteins were identified, 340 of them differentially expressed with minimum of 2 fold change and based on ≥2 unique peptides. Bioinformatics analysis of this dataset also revealed important molecular networks and pathways relevant to tumorigenesis, mTOR signaling pathway being a major pathway identified. Comparison of 340 differentially expressed proteins with the transcript data from Grade II diffuse astrocytomas reported earlier, revealed about 190 of the proteins correlate in their trends in expression. Considering progressive and recurrent nature of these tumors, we have mapped the differentially expressed proteins for their secretory potential, integrated the resulting list with similar list of proteins from anaplastic astrocytoma (WHO Grade III) tumors and provide a panel of proteins along with their proteotypic peptides, as a resource that would be useful for investigation as circulatory plasma markers for post-treatment surveillance of DA patients.

Characterization of the blood brain barrier in pediatric central nervous system neoplasms.

ObjectiveThe normal blood–brain barrier (BBB) is composed of tight junctions between endothelial cells and surrounding astrocyte foot processes. Breakdown of the physiological astrocyte-endothelial cell relationship occurs in adult metastatic and primary brain tumors. However, the astrocyte-endothelial cell relationship has not been studied in pediatric tumors.Materials and MethodsUtilizing specimens from cases of pilocytic astrocytoma (n = 5), medulloblastoma (n = 5), and low-grade diffuse astrocytoma (n = 1), immunofluorescence were performed using primary antibodies against CD31, glial fibrillary acidic protein (GFAP), and aquaporin 4 (AQ4). Clinical, magnetic resonance imaging, operative, and histopathological findings were analyzed.ResultsStrongly-enhancing areas of medulloblastoma exhibited complete BBB breakdown with sparse GFAP and AQ4 staining around CD31-positive vessels. Moderately enhancing regions of pilocytic astrocytomas exhibited regions of intact BBB and vasculature surrounded by dense GFAP staining but reduced and disorganized AQ4 staining, suggesting tumor cells could not fulfill physiological BBB support. Non-enhancing low-grade diffuse astrocytoma demonstrated intact BBB with intense peri-microvasculature GFAP and AQ4 staining. AQ4 stained so strongly that AQ4 visualization alone delineated CD31-positive vessels.ConclusionTaken together, BBB breakdown in pediatric tumors corresponds to a loss of normal endothelial cell-astrocyte foot process relationships. Further development of pharmaceutical agents capitalizing on this disrupted BBB is warranted in medulloblastoma and pilocytic astrocytoma. However, BBB integrity remains a challenge in treating low-grade diffuse astrocytoma before progression toward secondary glioblastoma.

Radial expansion rates and tumor growth kinetics predict malignant transformation in contrast-enhancing low-grade diffuse astrocytoma.

Contrast-enhancing low-grade diffuse astrocytomas are an understudied, aggressive subtype at increased risk because of few radiographic indications of malignant transformation. In the current study, we tested whether tumor growth kinetics could identify tumors that undergo malignant transformation to higher grades. Thirty patients with untreated diffuse astrocytomas (WHO II) that underwent tumor progression were enrolled. Contrast-enhancing and T2 hyperintense tumor regions were segmented and the radius of tumor at two time points leading to progression was estimated. Radial expansion rates were used to estimate proliferation and invasion rates using a biomathematical model. Radial expansion rates for both contrast-enhancing (p = 0.0040) and T2 hyperintense regions (p = 0.0016) were significantly higher in WHO II-IV tumors compared with nontransformers. Similarly, model estimates showed a significantly higher proliferation (p = 0.0324) and invasion rate (p = 0.0050) in WHO II-IV tumors compared with nontransformers. Tumor growth kinetics can identify contrast-enhancing diffuse astrocytomas undergoing malignant transformation.

Landscape of chromosomal copy number aberrations in gangliogliomas and dysembryoplastic neuroepithelial tumours.

Gangliogliomas (GGs) and dysembryoplastic neuroepithelial tumours (DNTs) represent the most common histological entities within the spectrum of glioneuronal tumours (GNTs). The wide variability of morphological features complicates histological classification, including discrimination from prognostically distinct diffuse low-grade astrocytomas (AIIs). This study was performed to increase our understanding of these tumours. We studied chromosomal copy number aberrations (CNAs) by genome-wide sequencing in a large cohort of GNTs and linked these to comprehensive histological analysis and clinical characteristics. One hundred fourteen GNTs were studied: 50 GGs and 64 DNTs. Also, a data set of CNAs from 38 diffuse AIIs was included. The most frequent CNAs in both GGs and DNTs were gains at chromosomes 5 and 7, often concurrent, and gain at chromosome 6. None of the CNAs was linked to histological subtype, immunohistochemical features or to clinical characteristics. Comparison of AIIs and diffuse GNTs revealed that gain at whole chromosome 5 is only observed in GNTs. CNA patterns indicative of chromothripsis were detected in three GNTs. We conclude that GNTs with diverse morphologies share molecular features, and our findings support the need to improve classification and differential diagnosis of tumour entities within the spectrum of GNTs, as well as their distinction from other gliomas.

Injury to Insult: Infarction After Radiotherapy in the Treatment of Pediatric Brain Tumor

This four-year-old boy underwent a subtotal resection of a large infiltrative brainstem mass extending into the left cerebellar peduncle (Fig 1A). Histopathology demonstrated a low-grade diffuse astrocytoma (World Health Organization grade II). Treatment included three-dimensional, conformal radiotherapy (54 Gy) and temozolomide chemotherapy. Thirty-two months after cranial irradiation, he presented with lethargy, dysarthria, worsening ataxia, and mild right-sided distal limb weakness with no history of trauma or infections.

O8.03 * LOW GRADE DIFFUSE ASTROCYTOMA - PROGNOSTIC FACTORS TO ANAPLASTIC TRANSFORMATION

INTRODUCTION: Low grade gliomas (LGG) comprise nearly 20% of all central nervous system (CNS) glial tumors. LGG are characterized by their infiltrative growth and frequent tumor recurrence with malignant progression. They have a heterogeneous clinical behavior being histological, first line resection, velocity of diameter tumor expansion during pretherapeutic period,tumor volume, contrast enhancement and patients' characteritics the only described factors for identifying patients at risk of progression. The identification and validation of new imaging prognostic factors would help to minimize potential treatment-related side effects in LGG. OBJECTIVE: The aim of our study was to analyze the impact of clinical (gender, age, first symptom), histological (gemistocytic) and neuroimaging (tumor growth ratio at 6 months- GR6m) factors on malignant progression in a cohort of diffuse low grade astrocytomas. We conducted serial volumetric analysis using Flair sequences. The time to malignant progression (TMP) was defined as time between histological diagnose and first MRI showing contrast enhancement or histology proven progression. RESULTS: Patients' mean age was 42.5 ± 14.6 years with a male:female ratio of 1.7:1. Median Pignatti index (PI) was 2 (1-4). The median TMP was of 4.76 (0.33-11.8) years. Nearly half (48.2%) of the patients showed a malignant progression. This group had a higher GR6m (49% versus 3%, p = 0.032). A cut-point of GR6m < 2% obtained by ROC analysis showed a sensitivity and specificity of 92.3% and 71% (p = 0.001). In the multivariate analysis the GR6m < 2% (HR: 5.23, 95% CI (1.4-19.61), P = 0.014), gemistocytic component (HR 8, 95% CI (1.6-39.3), p = 0.01) and a PI of 3-4 (HR : 6.94, 95% CI (1.64-29.4), p = 0.008) were identified as independent predictors of TMP. CONCLUSIONS: GR6m resulted as independent prognostic factor of TMP. In addition, our study confirmed PI and gemystocitic histology as prognostic factors on TMP.It is important to define new prognostic factors to anaplastic transformation due to individualized treatment in patients.

Modulation of HJURP (Holliday Junction-Recognizing Protein) Levels Is Correlated with Glioblastoma Cells Survival

BackgroundDiffuse astrocytomas are the most common type of primary brain cancer in adults. They present a wide variation in differentiation and aggressiveness, being classified into three grades: low-grade diffuse astrocytoma (grade II), anaplastic astrocytoma (grade III) and glioblastoma multiforme (grade IV), the most frequent and the major lethal type. Recent studies have highlighted the molecular heterogeneity of astrocytomas and demonstrated that large-scale analysis of gene expression could help in their classification and treatment. In this context, we previously demonstrated that HJURP, a novel protein involved in the repair of DNA double-strand breaks, is highly overexpressed in glioblastoma.Methodology/Principal FindingsHere we show that HJURP is remarkably overexpressed in a cohort composed of 40 patients with different grade astrocytomas. We also observed that tumors presenting the higher expression levels of HJURP are associated with poor survival prognosis, indicating HJURP overexpression as an independent prognostic factor of death risk for astrocytoma patients. More importantly, we found that HJURP knockdown strongly affects the maintenance of glioblastoma cells in a selective manner. Glioblastoma cells showed remarkable cell cycle arrest and premature senescence that culminated in elevated levels of cell death, differently from non-tumoral cells that were minimally affected.ConclusionsThese data suggest that HJURP has an important role in the maintenance of extremely proliferative cells of high-grade gliomas and point to HJURP as a potential therapeutic target for the development of novel treatments for glioma patients.

Abstract 2406: Intra-tumoral heterogeneity of PDGFRA / MET gain in WHO grade II diffuse astrocytomas.

Abstract Glioblastomas with a proneural expression signature are characterized by frequent IDH1 mutations (i.e. genetic hallmarks of secondary glioblastomas) and PDGFRA amplification. Most glioblastomas with IDH1 mutations (11/12, 92%) show a proneural signature, the majority with wild-type PDGFRA, while approximately 30% of glioblastomas with a proneural signature had IDH1 mutations. IDH1/2 mutations are frequent and early genetic events in diffuse astrocytomas WHO grade II, precursor to secondary glioblastomas, but little is known about the role and timing of PDGFRA amplification in these tumors. In the present study, we assessed PDGFRA gain in 342 low-grade diffuse gliomas (166 low-grade diffuse astrocytomas, as well as 61 oligoastrocytomas and 115 oligodendrogliomas) by quantitative PCR. PDGFRA gain was detected in 27/166 (16.3%) diffuse astrocytomas, significantly more frequent than in oligoastrocytomas (6.6%; P=0.04) or in oligodendrogliomas (3/115; 2.6%; P&amp;lt;0.0001). We correlated PDGFRA gain with other genetic alterations in low-grade diffuse gliomas previously reported from our laboratory. PDGFRA gain was significantly more frequent in diffuse astrocytomas, oligodendrogliomas and low-grade diffuse gliomas without IDH1/2 mutations than those with IDH1/2 mutations (36.8% vs 13.6%; P=0.018, 16.7% vs 1.0%; P=0.028, 24.3% vs 8.3%; P=0.006, respectively). PDGFRA gain was most frequent (28.6%) in gliomas lacking any of common genetic alterations (IDH1/2 mutations, TP53 mutations and 1p/19q loss). PDGFRA gain was found in low-grade diffuse gliomas with TP53 mutation ± IDH1/2 mutations (16.3%) and those with IDH1/2 mutation only (10.5%), but rare in tumors with 1p/19q loss ± IDH1/2 mutations (1.4%). In diffuse astrocytomas, PDGFRA gain positively correlated with MET gain (P=0.016) and inversely correlated with 1p/19q loss (P=0.005) and IDH1/2 mutations (P=0.018). The vast majority of diffuse astrocytomas showed IDH1/2 mutations and/or PDGFRA gain (154/166; 93%). Mean survival of diffuse astrocytoma patients with PDGFRA gain was 8.8 ± 1.6 years, similar to that with IDH1/2 mutations (7.8 ± 0.5 years) or TP53 mutations (7.6 ± 0.6 years), but significantly longer than those with MET gain (4.4 ± 0.7 years). The mean survival of diffuse astrocytoma patients with co-gain of MET and PDGFRA was 7.7 ± 2.0 years, which was similar to those with PDGFRA gain only. Dual-color FISH in 6 diffuse astrocytomas with PDGFRA / MET co-gain identified by quantitative PCR revealed PDGFRA and MET were typically amplified in different tumor cell populations within the tumor, but tumor cells with co-amplification were also focally observed, suggesting intra-tumoral heterogeneity even in diffuse astrocytomas. Citation Format: Kazuya Motomura, Michel Mittelbronn, Werner Paulus, Benjamin Brokinkel, Kathy Keyvani, Ulrich Sure, Karsten Wrede, Yoichi Nakazato, Yuko Tanaka, Naosuke Nonoguchi, Daniela Pierscianek, Young-Ho Kim, Luigi Mariani, Anne Vital, Arie Perry, Hiroko Ohgaki. Intra-tumoral heterogeneity of PDGFRA / MET gain in WHO grade II diffuse astrocytomas. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2406. doi:10.1158/1538-7445.AM2013-2406

The Definition of Primary and Secondary Glioblastoma

Glioblastoma is the most frequent and malignant brain tumor. The vast majority of glioblastomas (~90%) develop rapidly de novo in elderly patients, without clinical or histologic evidence of a less malignant precursor lesion (primary glioblastomas). Secondary glioblastomas progress from low-grade diffuse astrocytoma or anaplastic astrocytoma. They manifest in younger patients, have a lesser degree of necrosis, are preferentially located in the frontal lobe, and carry a significantly better prognosis. Histologically, primary and secondary glioblastomas are largely indistinguishable, but they differ in their genetic and epigenetic profiles. Decisive genetic signposts of secondary glioblastoma are IDH1 mutations, which are absent in primary glioblastomas and which are associated with a hypermethylation phenotype. IDH1 mutations are the earliest detectable genetic alteration in precursor low-grade diffuse astrocytomas and in oligodendrogliomas, indicating that these tumors are derived from neural precursor cells that differ from those of primary glioblastomas. In this review, we summarize epidemiologic, clinical, histopathologic, genetic, and expression features of primary and secondary glioblastomas and the biologic consequences of IDH1 mutations. We conclude that this genetic alteration is a definitive diagnostic molecular marker of secondary glioblastomas and more reliable and objective than clinical criteria. Despite a similar histologic appearance, primary and secondary glioblastomas are distinct tumor entities that originate from different precursor cells and may require different therapeutic approaches.