Brain Tumors Research Articles

SURG-04. DEVELOPMENT OF MICROSURGICAL FORCEPS EQUIPPED WITH HAPTICS TECHNOLOGY FOR IN SITU DIFFERENTIATION OF BRAIN TUMORS DURING MICROSURGERY

Abstract BACKGROUND The stiffness of human cancers is correlated with their pathology, and can be used as a biomarker for diagnosis, malignancy prediction, molecular expression, and postoperative complications. Neurosurgeons perform tumor resection based on tactile sensations. However, it takes years of surgical experience to appropriately distinguish brain tumors from surrounding parenchymal tissue. Haptics is a technology that can amplify, transmit, record, and reproduce real tactile sensation, and the physical properties (e.g., stiffness) of an object can be quantified. METHODS glioblastoma (SF126-FmC, U87-FmC, U251-FmC) and malignant meningioma (IOMM-Lee-FmC, HKBMM-FmC) cell lines were transplanted into nude mice, and the stiffness of tumors and normal brain tissues were measured using our newly developed surgical forceps equipped with haptic technology (haptic forceps). Furthermore, pathological examination was performed to explore the correlation between stiffness and histological characteristics. RESULTS We found that all five brain tumor tissues were stiffer than normal brain tissue (p<0.001), and that brain tumor (three types of glioblastomas and two types of malignant meningioma) was significantly stiffer than normal brain tissue (p<0.001 for all). The stiffness among glioblastomas was not statistically significant (p=0.468) however, among the 2 malignant meningiomas, IOMM-Lee-FmC was significantly stiffer than HKBMM-FmC (p=0.032). Upon pathological examination, no significant differences were observed in the expression of collagen fibers. However, HKBMM-FmC demonstrated a higher prevalence of necrotic changes compared to IOMM-Lee-FmC. CONCLUSIONS Our findings suggest that tissue stiffness could be a marker not only to distinguish brain tumors from surrounding parenchymal tissue but also to distinguish pathology and malignancy of tumors. It is also suggested that the stiffness perceived during actual surgery and the stiffness quantified using haptic forceps may correlate with histological differences. Haptic forceps may help neurosurgeons to sense minute changes in tissue stiffness.

DDDR-09. POTENTIAL OF GSPT1 AS A NOVEL TARGET FOR GLIOBLASTOMA THERAPY

Abstract Glioblastoma is the most common malignant brain tumor in adults, the survival rate of which has not significantly improved over the past three decades. Therefore, there is an urgent need to develop novel treatment modalities. We have reported G1 to S phase transition 1 (GSPT1) as a novel downstream target of RAC1, which is a tumor driving and promoting molecule, and that depletions of GSPT1 as well as RAC1 induced delayed cell cycle progression in primary astrocytes. Herein, we examined the potential of GSPT1 as a novel target for glioblastoma therapy. CC-885, a cereblon modulator that degrades GSPT1 by bridging GSPT1 to CRL4 E3 ubiquitin ligase complex, was administered to nude mice with transplanted brain tumors of U87 glioblastoma cells. The survival period was significantly longer in CC-885 treated mice than in control mice. Furthermore, we generated GSPT1-knockout (KO) U87 cells by genome editing and GSPT1-KO U87 cells with stable overexpression of FLAG-tagged GSPT1 (Rescued GSPT1-KO U87 cells). Mice with transplanted GSPT1-KO U87 cells and Rescued GSPT1-KO U87 cells showed significantly longer and similar survival periods, respectively, as those with WT U87 cells. GSPT1-KO U87 cells showed enhanced apoptosis, detected by cleaved PARP1, compared to WT U87 cells. Brain tumors due to transplantation of GSPT1-KO U87 cells also showed enhanced apoptosis compared to those due to transplantation of WT and Rescued GSPT1-KO U87 cells. GSPT1 expression was confirmed in patients with glioblastoma. However, the clinical study using 87 glioblastoma samples showed that GSPT1 mRNA levels were not associated with overall survival. Taken together, we propose that GSPT1 is an essential protein for glioblastoma growth, but not its malignant characteristics, and that GSPT1 is a potential target for developing glioblastoma therapeutics.

INNV-10. ULTRA-RAPID INTRAOPERATIVE GLIOMA TUMOR CELL QUANTIFICATION

Abstract The diagnosis and treatment of brain tumors often depends on molecular-genetic data. To date, however, there has been no intraoperative method to rapidly and iteratively utilize tumor-specific genetic alterations to guide brain tumor surgical resections, complicating intraoperative diagnosis and precluding measurement of tumor cell burdens at surgical margins. To address this gap, we developed Ultra-Rapid droplet digital PCR (UR-ddPCR), which can be completed in 15 minutes from tissue to result with an accuracy and sensitivity comparable to standard ddPCR. We demonstrate an UR-ddPCR assay for the IDH1 R132H clonal mutation that is present in many low-grade gliomas. We illustrate the clinical feasibility of UR-ddPCR by performing it intraoperatively for 49 samples from 13 glioma cases, achieving intraoperative quantification in an average of 14 minutes and 54 seconds spanning a wide dynamic range from 0.1% to 94% tumor cell percentages. We further combine UR-ddPCR measurements with UR-stimulated Raman histology intraoperatively to estimate tumor cell densities in addition to tumor cell percentages, across a wide range from < 1 to 1332 cells/mm2. We anticipate that UR-ddPCR, along with future refinements in assay instrumentation, will enable novel point-of-care diagnostics and the development of molecularly-guided brain tumor surgeries that improve clinical outcomes.

CNSC-30. DETERMINING THE REGULATION AND FUNCTION OF ANGPT1 HIGH-GRADE GLIOMAS

Abstract Angiopoietin-1 (Angpt1) is a secreted protein that promotes angiogenesis and vascular stability in development and certain disease states through activation of the Tie2 receptor. However, little is known about its regulation and function in brain tumors. Angpt1 is upregulated in glial brain tumors, including high-grade gliomas and ependymomas. We find Angpt1 is expressed by specific cell populations within gliomas, along with non-tumor reactive astrocytes and perivascular mural cells. Leveraging an in vivo brain tumor modeling system we have generated glioma models to investigate how tumor cell state impacts Angpt1 expression, along with creating Angpt1 knock-out models. We find that Angpt1 expression is increased when glioma models are biased towards a more astrocytic and/or mesenchymal state, mirroring developmental expression patterns. Ongoing studies utilizing these models are being used to determine the mechanisms that regulate the dynamic expression of Angpt1 and its function in glioma pathogenesis, including tumor angiogenesis and blood-brain barrier function.

EPCO-47. SEX-BIASED BRD4 ACTIVITY DRIVES TUMORIGENESIS IN GLIOBLASTOMA

Abstract Consistent sex differences in incidence and outcome have been reported in cancers including brain tumors. Glioblastoma (GBM), the most common and aggressive primary brain tumor, occurs with higher incidence and shorter survival in males compared to females. Brd4 is essential for regulating transcriptome-wide gene expression and specifying cell identity. Using an isogenic murine GBM model, we have reported correlated transcriptome-wide sex differences in gene expression, Brd4-bound enhancer usage, and Brd4 localization to oncogenic and tumor suppressor transcription factors binding sites in male and female GBM cells, respectively. Sex-biased gene expression patterns were also evident in human glioblastoma. Inhibiting Brd4 function abrogates sex differences in these transcriptional states and concomitant differences in tumorigenic phenotype. Thus, sex-biased Brd4 activity drives sex differences in GBM rendering males and females differentially sensitive to BET inhibitors. These data indicate that Brd4 can exhibit dual functions as an oncogene or tumor suppressor, dependent upon cellular sex. To better understand how to globally target Brd4, we interrogated the role played by master transcriptional Brd4 regulators in coordinating this dual phenotype in GBM. Motif-based analysis revealed that Brd4 co-localized with oncogenes such as Bach1, and Klf5 at male-biased enhancers whereas female-biased enhancers were co-occupied with tumor suppressors, such as Smad4 and p53. Knockdown of Bach1 decreased clonogenic frequency in males and females. Conversely, knockdown of Smad4 increased proliferation and clonogenicity in males, further inducing the male tumorigenic phenotype, while no change was observed in females. These results indicate that Smad4 might be necessary but not sufficient to provide females with resistance to transformation. Ongoing epitranscriptomics investigating Brd4 re-localization and enhancer usage in knockdown cells will increase our understanding of Brd4 mechanism in GBM. Targeting sex-biased Brd4 function will identify novel combinatorial sex-specific therapeutics for brain tumors and could have immediate impact on the clinical treatment of GBM patients.

TMET-20. A METABOLIC BIOMARKER IN GLIOBLASTOMA: A PROMISING APPLICATION OF CO-POLARIZED [1-13C]PYRUVATE AND [1-13C]DEHYDROASCORBATE

Abstract BACKGROUND Noninvasive biomarkers for treatment response in glioblastoma are needed to improve patient outcomes. Our understanding of redox biology in treatment resistance is rapidly evolving, and interrogation of tumor metabolism represents an ideal opportunity to meet this need. In this study, the utility of co-hyperpolarized [1-13C]pyruvate and [1-13C]dehydroascorbate (HP PA/DHA) to simultaneously evaluate brain tumor metabolism and oxidative stress in orthotopically implanted mice is investigated. METHODS To characterize HP PA/DHA, mice were treated with 0-4mM diethyl maleate and 1D slab dynamic acquisitions were performed over the mouse brain. As an initial evaluation of the utility of HP DHA/PA in brain tumors, athymic nude mice (n=8) underwent orthotopic U87 glioblastoma implantation. After treatment with 8Gy in one fraction, mice were injected with HP DHA/PA dissolved in D2O. T2-weighted and 13C Chemical Shift Imaging sequences were obtained on a 3T MRI using a quadrature double-tuned 1H/13C volume coil. RESULTS HP DHA/PA detected differential lactate and vitamin C generation over the mouse brain. Treatment with diethyl maleate, which depletes the cofactor glutathione, diminished fractional vitamin C generation (0.1 vs 0.03, p=0.0009). Elevation in tumor lactate generation was seen in untreated (125.1±17.6µM, p=0.005) and radiated mice (149.4±32.6µM, p=0.01). Treatment with radiation generated higher vitamin C concentrations in tumors relative to contralateral brain (46.8±4.8µM, p=0.002). Radiated tumors were distinguished by higher ratio of lactate to vitamin C compared to untreated tumor controls (3.7 vs 2.5, p=0.07), and the same relationship was preserved between treated and untreated non-tumor brain. CONCLUSION The ratio of vitamin C/lactate detects the metabolic effects of radiation in brain tumors, inspiring its’ potential as a biomarker for treatment response. To further characterize these findings, examination of survival and modulation of radiosensitivity are ongoing.

BIOM-10. CLINICAL PERFORMANCE EVALUATION OF A BRAIN CANCER LIQUID BIOPSY

Abstract Diagnostic delays impact the quality of life and survival of patients with brain cancer. Currently, with no blood test to assist them, clinicians must make their referral decision based on symptoms. Existing symptom-based referral guidelines inadequately stratify patients for brain imaging based on suspicion of cancer. A simple, rapid liquid biopsy placed in a primary care setting would enable more efficient triage of patients with non-specific symptoms related to brain cancer. The Dxcover® Liquid Biopsy is a rapid multi-omic liquid biopsy that interrogates a blood sample with infrared radiation and produces a distinctive signature that represents the whole biomolecular profile of the sample, and is sensitive to the hallmarks of brain cancer. The nature of the technology also allows for the diagnostic models to be tailored towards higher sensitivity (or specificity) depending on clinical priorities and international healthcare markets. In initial feasibility studies, we recruited 988 patients prospectively with non-specific symptoms associated with a brain tumor, and the algorithm detected 96% of the patients with brain tumors and 100% of glioblastomas (GBM), when tuned for greater sensitivity. EMBRACE is a prospective, observational, multicenter study, currently recruiting patients across seven sites in the United Kingdom, Belgium, Sweden and Switzerland. The study duration is 24 months and will recruit a minimum of 2200 participants. The target population is comprised of patients presenting to primary care with non-specific symptoms that are associated with brain cancer, such as headache and new onset neurological defect. The primary objective is to determine the clinical performance of the liquid biopsy for patients with brain cancer, in terms of diagnostic sensitivity and specificity. The test performance will be determined by comparing the liquid biopsy result to diagnostic imaging. Earlier and expeditious diagnoses in these patients are crucial to reduce the morbidities and mortalities associated with brain cancer. This simple, non-invasive liquid biopsy would facilitate the triage of brain tumor patients for rapid imaging.

EXTH-20. EXPLORING EUPHOL’S THERAPEUTIC EFFECT IN ADULT AND PEDIATRIC BRAZILIAN HIGH-GRADE GLIOMAS PRE-CLINICAL MODELS

Abstract High grade gliomas (HGG) are among the most aggressive brain tumors affecting both adults and children. Adult HGG (aHGG) account for almost 25% of all brain tumors in adults, with glioblastoma (GBM) being the predominant subtype. Pediatric HGG (pHGG), though less common, accounts for 3-15% of primary brain tumors in children and exhibits distinct genetic profiles compared to aHGG. Standard treatment for HGG in both adults and pediatric patients includes maximal surgical resection followed by temozolomide (TMZ)-based chemotherapy and radiation therapy. Our group previously reported that euphol, a natural compound derived from the sap of Euphorbiaceae family plants, exerts cytotoxicity effects on glioma cells. In this study, we investigated the therapeutic potential of euphol in primary cell cultures and xenograft models derived from six Brazilian HGG patients, including three adults and three pediatrics. In vitro, euphol exposure significantly reduced cell viability reduction, clonogenic capacity, and migration, while enhancing apoptosis in all six primary cultures. Additionally, euphol sensitized glioma cells to TMZ, resulting in a synergistic cytotoxic effect. In vivo, euphol reduced tumor growth in both GBM and pHGG models, and prolonged the survival of mice in the GBM orthotopic experiment. These findings highlight the promising therapeutic potential of euphol for treating high-grade gliomas in both adult and pediatric populations.

CSIG-06. BRAF GERMLINE MUTATIONS AND PREDISPOSITION TO BRAIN TUMORS

Abstract We report on two BRAF-mutated children and discuss genetic counseling regarding predisposition to brain tumors. Molecular analysis of the PTPN11 gene and twelve other genes in the RAS-MAPK pathway was carried out in a series of 54 dysmorphic patients with suspected Rasopathies. Two heterozygous BRAF germline mutations were detected in two 7-year-old girls, at exon 6 and 12 respectively. Both patients had the distinctive facial appearance of cardio-facio-cutaneous syndrome (CFC) type 1. Patients with CFC are rare and characterized by phenotypic and genetic heterogeneity, with overlaps with Noonan syndrome. While nearly 75% of CFC cases have germline BRAF mutations, the frequency of BRAF mutations is inferior in Noonan and LEOPARD syndromes. BRAF mutations in CFC are often found in the cysteine-rich domain of the BRAF protein (exons 6, 11, 12, 13, 14, 15 and 16). Conversely, somatic BRAF mutations are more common, grouped into classes according to their kinase activity level, and have been associated with a variety of malignancies, including pediatric and adult brain tumors (low- and high-grade gliomas, glioblastomas and low-grade astrocytomas). BRAF V600E is the most common somatic mutation, but other mutations are currently being identified. Many of these mutations are within the kinase domain, while others are located across the gene and have less well-understood functional consequences. Germinal V600E mutation has been described once, in a CFC patient having a severe phenotype. Nevertheless, it seems that patients with germline BRAF mutations and gliomas have not yet been reported. Given the rarity of CFC, it is unclear whether there is a high risk of brain tumors. Further molecular studies will enable us to refine recommendations for the prevention, monitoring and care of people with germline BRAF mutations, given the success of BRAF inhibitors in certain cancers, with encouraging results in gliomas.

IMMU-07. THE IMMUNE LANDSCAPE OF PEDIATRIC BRAIN TUMORS: A TRANSCRIPTOMIC ANALYSIS

Abstract Despite standard-of-care therapy, pediatric brain tumors are now the leading cause of cancer-related death in children, highlighting an urgent need for the development of new treatments. Immunotherapy is actively being evaluated as a therapeutic approach to pediatric brain tumors, however, more research is needed to reveal additional antigenic targets that exist in these malignancies. In this study, our team performed a transcriptomic analysis of pediatric brain tumor RNA sequencing data within the Children’s Brain Tumor Network (CBTN) to identify intra and extracellular antigens that are highly expressed across major tumor types. Interestingly, our team observed that most tumors had high gene expression of a group of antigens that were unique to that specific tumor type. Specifically, our analysis revealed that diffuse midline gliomas (DMGs) highly expressed the extracellular antigens CA9, CTCFL, and ST8SIA1, whereas atypical rhabdoid tumors (ATRTs) highly expressed MUC1 and TEK. Other tumors that displayed high gene expression for a variety of antigenic targets included H3-wildtype high-grade gliomas (HGGs), and ependymomas (EPNs). Strikingly, we observed minimal difference in antigen expression in primary tumors when compared to patient-matched recurrences. Beyond antigen expression, we evaluated the expression of antigen processing machinery (APM) which includes major histocompatibility complexes (MHCs). Our findings revealed that DMGs had the lowest level of APM expression, however, these tumors uniquely expressed high levels of the immune checkpoints ADORA2A, CD276, and KLRC1. Contrarily, ATRTs showed a high expression of immune checkpoints CD274 (PD-L1), PVR, and CD80. Other tumors included in our analysis had unique expression patterns of antigen, as well as APM and immune checkpoints. Our findings illustrate that pediatric brain tumors have distinct expression patterns of antigens, APM, and immune checkpoints that are specific to tumor type, emphasizing diverse, rather than general, immunotherapeutic approaches must be considered for childhood brain tumors.

NIMG-26. GLIOBLASTOMA TISSUE INVASION MAPPING WITH NOVEL HYPOXIA-TARGETED BLOOD OXYGENATION-LEVEL DEPENDENT MRI

Abstract BACKGROUND Glioblastoma is a devastating incurable malignant primary brain tumor exhibiting an erratic growth pattern and brain tissue invasion exceeding the typically depicted contrast-enhancing lesion on MRI. This behaviour is strongly associated with the presence of aberrant vasculature. Advanced clinical neuroimaging techniques, however, have not provided convincing imaging markers to determine glioblastoma tissue infiltration and monitor treatment effects. We investigated a new imaging technique based on blood oxygenation-level dependent (BOLD) MRI contrast with precise hypoxic respiratory targeting in order to better determine tumor tissue invasion not restricted to the typically depicted focal glioblastoma lesion on contrast-enhanced MRI. METHODS A computer-controlled gas blender was used to induce transient and standardized hypoxic stimulus in isocapnic conditions during echo-planar-imaging acquisition in patients with brain tumors.8,9 Data were preprocessed using SPM and in-house written MATLAB scripts. The induced BOLD signal changes were used to calculate %BOLD signal change during hypoxic stimulus with respect to the baseline, contrast to noise (CNR) ratio and goodness-of-fit (Rsquared) for each voxel in the whole-brain and automatically segmented region of interest (contrast-enhancement, necrosis, edema) and overlayed using color-maps onto anatomical high resolution T1. RESULTS Hypoxic targeting during gas modulation could be performed with high reproducibility, caused no discomfort in patients with brain tumors and was able to induce strong signal change during hypoxic stimulus with high contrast-noise ratio and Rsquared. In particular, when compared with other tumors, BOLD hypoxia glioblastoma tissue invasion maps show very distinct hypoxic signal responses in some cases extending beyond the focal -contrast-enhancing- glioblastoma lesion. CONCLUSION The ability to map at voxel level BOLD hypoxia signal patterns may determine a novel therapeutic imaging marker based on structural vascular alterations in the tumour tissue infiltration zone before these become appreciable with standard neuroimaging. This may support a refinement and tailoring of tumor resection and improve follow-up after resection and during treatment i.e. chemoradiotherapy.

NIMG-33. HIGH-RESOLUTION SODIUM MRI OF HUMAN GLIOMAS AT 3T USING PHYSICS-BASED GENERATIVE AI

Abstract BACKGROUND Sodium neuroimaging is a promising technique for diagnosing and monitoring brain tumors, providing insights into microenvironment and metabolism. However, at 3T, it is limited by low signal-to-noise ratio and resolution, resulting in long acquisition times and low-quality images. To address these limitations, we developed a physics-informed generative adversarial network (GAN) approach for high-resolution sodium neuroimaging of brain tumors at 3T. METHODS 5,078 anatomical sequences from 1,330 brain tumor patients undergoing routine proton MRI were used to create a synthetic dataset with physics-based simulated artifacts, including B0 magnetic susceptibility artifacts, chemical shift artifacts, Nyquist aliasing artifacts, Gibbs artifacts, and low-resolution images, with Rician noise added during training to augment the dataset. By using multiple proton MRI contrasts, we hypothesized that the GAN model would learn to correct artifacts while preserving the inherent contrast information. We employed a transfer learning approach with a modified Pix2PixGAN architecture and an Attention-R2UNet generator. Twenty glioma patients consented to participate in this IRB-approved prospective study. Sodium and proton MRIs were acquired in the same sessions using a 3T Siemens scanner using a dual-tuned head coil, with a 3D spoiled gradient-echo sequence optimized for short TE. Sodium-proton exchanger (NHE1) expression was tested with immunohistochemistry from image-guided surgical biopsies. RESULTS High-resolution synthetic-sodium MR images were generated using the GAN model. The proposed method successfully reconstructed high-resolution synthetic-sodium MR images with improved SNR compared to traditional sodium images. Synthetic and native measurements were strongly correlated (R2=0.8539, P<0.0001). A significant correlation was seen between synthetic-sodium MR measurements and relative NHE1 tissue expression (ρ=0.5817, P=0.0036). CONCLUSION Results suggest that high-resolution synthetic-sodium MRI retains much of the inherent information from native sodium MR while accurately representing NHE1 expression. This approach could make high-resolution sodium neuroimaging at 3T feasible in the clinical environment, potentially improving diagnosis, monitoring, and treatment of brain tumors.

SURG-33. INTRAOPERATIVE ULTRASSOUND X SODIUM FLUORESCEIN FOR GLIOMA SURGERY: WHICH IS BETTER?

Abstract BACKGROUND Improve quality of life with a maximum surgical resection is the main goal of neurosurgeons. A better delimitation of intrinsic brain tumors are required for achieving a maximum tumor removal. There are several technologies that may help. Considering two of them that have an easier access and are cheaper, we compared a high definition ultrasound (BK 3000) and sodium fluorescein (SF) during glioma surgeries. METHODS Adult patients with main radiological hypothesis of low or high grade glioma were included in a PhD study previously approved by ethics committee. 3-5mg/kg of SF was administered by intravenous infusion during anesthetic induction. An specific craniotomy transducer was used in all cases. All procedures were guided by the same neurosurgeon. RESULTS High definition ultrasound allows an excellent tumor delimitation in high and low grade tumors. However the gray scale and distinction of brain structures and residual lesion was difficult for surgeons who are not habituated to ultrasound use. SF did not help low grade glioma removal, and in these cases ultrasound were superior. Increased fluorescence is easily detected when compared to ultrasound information’s. For small residual tumor, SF helps more than US. For both technologies, when the surgical site had blood, the evaluation about grade of resection is not accurate because in ultrasound appears a posterior shadow and considering SF it seems that there are not further tumor because blood does not have increased fluorescence. CONCLUSIONS US showed superiority for low grade gliomas resection. Considering high grade, both technologies helps in different moments during the surgery and are complimentary. We used an specific probe for neurosurgery that has high quality and allowed detailed evaluations. These technologies helps surgeons take quick decision and optimized brain tumor removal. The neurosurgeon should be more familiar to US images because provide a real time evaluation with low cost. KEY WORDS: ultrasound; fluorescein; gliomas; brain tumors

EPID-33. EPITHELOID SARCOMA IN A LONG-TERM SURVIVOR OF AN ATYPICAL TERATOID / RHABDOID TUMOR WITH RHABDOID TUMOR PREDISPOSITION SYNDROME

Abstract INTRODUCTION Rhabdoid tumor predisposition syndrome (RTPS) predisposes to a high risk of developing Rhabdoid tumors in Brain, kidney; and is defined by a germline mutation in SMARCB1 (rarely SMARCA4) gene. The most frequent pediatric tumor associated with RTPS is atypical teratoid/rhabdoid tumor (ATRT), commonly diagnosed in children < 3 years of age. Epitheloid Sarcoma (ES) is a rare soft tissue sarcoma, arising in any age group and histologically defined by loss of SMARCB1 in tumor cells. METHODS We describe a long- term survivor of ATRT with RTPS presenting 12 years later with ES. Data was collected from medical chart review. RESULTS Our patient was diagnosed with ATRT and RTPS (SMARCB1) at 6 months of age and treated with chemotherapy as per ACNS0333 at diagnosis; by chemotherapy / focal radiation at first relapse and with alisertib on second relapse. At 10yrs of age she presented with multiple firm, skin-colored dermal nodules in both her hands (palms and fingers). She was diagnosed to have palmar warts and treated with topical cantharidin with a waxing and waning course. Subsequently the hand lesions were diagnosed as granuloma annulare and followed up with no therapy. At 12 years of age, lesion in tip of the right thumb increased in size and a punch biopsy was done which revealed ES with IHC showing loss of SMARCB1 in tumor cells. Staging CT of the chest showed multiple bilateral (b/l) small (<1cm) axillary lymph nodes with a negative PET scan. Bilateral axillary lymph node biopsies were negative for ES. She underwent excision of all the hand lesions with negative margins with no further therapy. CONCLUSION Based on our case and single case report in literature, we hypothesize that ES is likely a primary malignancy of RTPS and should be included in the spectrum of malignancies of RTPS.

NCMP-14. RADIOGRAPHIC RESPONSE TO BEVACIZUMAB IN TREATING RADIATION NECROSIS AND ASSOCIATED EDEMA IN BRAIN TUMORS

Abstract OBJECTIVE This study evaluates the efficacy of bevacizumab in treating radiation necrosis (RN) and associated perilesional edema in brain tumors. We aimed to measure changes in radiologic volumes and clinical performance following treatment. MATERIALS AND METHODS We retrospectively reviewed patients treated with radiation therapy and/or stereotactic radiosurgery between September 2017 and August 2023. We identified 10 metastatic brain tumors and one glioblastoma with symptomatic RN. Diagnosis was primarily through MRI, with one case confirmed pathologically. All patients received bevacizumab (7.5 mg/kg every 3 weeks). Volumes of RN and perilesional edema were measured using gadolinium-enhanced T1-weighted and T2-weighted/FLAIR MRI, respectively, analyzed with Brainlab software. Volume changes and clinical symptoms, graded by the ECOG Performance Status (PS) scale, were recorded. RESULTS The minimal follow-up was 4 months. The 11 patients received a median of 2 bevacizumab cycles (range, 2-3). Pre-treatment median volumes (ranges) were: tumor/RN 5.45 cc (2.66-13.56), perilesional edema (T2, FLAIR) 53.93 cc (7.46-115.32), 58.01 cc (15.18-131.2). Post-treatment median volumes (ranges) were: tumor/RN 2.5 cc (2.23-7.23), perilesional edema (T2, FLAIR) 4.05 cc (3.08-11.18), 7.38 cc (2.887-17.647). Median percentage volume reductions were: tumor 39%, RN 38%, perilesional edema (T2, FLAIR) 80%, 79%. Significant reductions in edematous volumes were observed. Pre-treatment ECOG PS median was 2 (range 2-3); post-treatment ECOG PS median remained 2 (range 2-3). Clinical performance improved in most patients, with two exception where deterioration occurred after the third cycle despite initial improvement. CONCLUSION Bevacizumab is effective in reducing RN and perilesional edema, particularly within the first two cycles of treatment. Most patients showed clinical improvement, though further research is needed to optimize treatment and understand long-term outcomes.

CTNI-37. INTERIM SAFETY ANALYSIS OF THE PHASE IB/II RANDOMIZED ANTI-GLUTAMATERGIC DRUG REPURPOSING TRIAL GLUGLIO IN PATIENTS WITH NEWLY DIAGNOSED GLIOBLASTOMA (NCT05664464)

Abstract The advent of cancer neuroscience has significantly advanced our understanding of brain tumor biology, yet the clinical implications remain largely unexplored. Glutamate, the most abundant excitatory neurotransmitter, presents a potential therapeutic target in brain tumors. Glioblastoma cells synthesize and secrete large amounts of glutamate, driving epilepsy, neuronal death, tumor growth, and invasion. Several brain-penetrating drugs, approved for other conditions, can inhibit glutamate synthesis, secretion, and signaling. These drugs include: (i) gabapentin, an anti-seizure medication that inhibits the glutamate synthesis enzyme branched-chain amino acid transaminase 1; (ii) sulfasalazine, an anti-inflammatory drug that blocks the cystine-glutamate exchanger system Xc, reducing glutamate secretion; and (iii) memantine, a cognitive enhancer that prevents glutamate-driven, calcium-induced neuronal death and tumor cell invasion by blocking N-methyl-D-aspartate type glutamate receptors. The multi-center, open-label, parallel-group, two-arm, 1:1 randomized phase Ib/II trial GLUGLIO is investigating the efficacy of a daily oral anti-glutamatergic triple combination of gabapentin, sulfasalazine, and memantine until tumor progression, in conjunction with standard chemoradiotherapy, compared to chemoradiotherapy alone. The primary endpoint is progression-free survival at 6 months (PFS-6). A sample size of 120 patients was determined to detect an increase in PFS-6 from 50% to 70%, with 80% power, using exploratory hypothesis testing at a one-sided significance level of 10%. Secondary endpoints include overall survival, seizure-free survival, response rate, quality of life for patients and caregivers, symptom burden, cognitive functioning, tumor glutamate levels (measured by magnetic resonance spectroscopy), and the use of anti-convulsants and steroids. Each drug is dosed up to the maximum approved amount. Results from the phase Ib part of the trial, including an interim safety analysis, will be presented at the conference.

TMIC-17. TARGETING THE FLUIDIC FORCE-SENSING MECHANISM TO TREAT BRAIN TUMOR METASTASIS

Abstract Biofluid flow generates fluid shear stress (FSS), a mechanical force widely present in tissue microenvironment. How brain tumor growth alters the conduit of biofluid, thereby impacting FSS-regulated cancer progression is unknown. Medulloblastoma (MB) is the most common malignant brain tumor in children. Dissemination of MB cells into the cerebrospinal fluid (CSF) initiates metastasis within the central nervous system. By simulating CSF dynamics based on magnetic resonance imaging of MB patients, we discovered that FSS is elevated at the cervicomedullary junction. Strikingly, we found that MB-relevant FSS promotes metastasis along mouse spinal cords. Mechanistically, FSS induces metastatic cell behaviours, including weakened cell-substrate adhesion, increased motility, cell clustering, and plasma membrane localization of glucose transporter 1 (GLUT1) to enhance glucose uptake. FSS is perceived by mechanosensitive ion channel PIEZO2, which drives actomyosin contractility-dependent GLUT1 recruitment at the plasma membrane. Genetic targeting of PIEZO2 or pharmacologic inhibition of GLUT1 mitigates metastasis. Collectively, these findings define a targetable FSS-activated mechano-metastatic cascade for the treatment of MB metastasis.

NCOG-04. MEMORY TRACT SPARING USING DIFFUSE TENSOR IMAGING IN RADIATION PLANNING OF PRIMARY BRAIN TUMORS

Abstract INTRODUCTION Radiation therapy (RT) is a critical treatment modality for both primary and metastatic brain tumors, yet approximately 30% of patients experience cognitive decline post-radiotherapy. This cognitive toxicity is linked to low radiation doses affecting neural stem cells in the hippocampal dentate gyrus. Hippocampal Avoidance (HA)-Whole Brain Radiotherapy (WBRT) combined with Memantine has shown promising outcomes in preserving cognitive function and quality of life (QOL) in patients with brain metastases, suggesting it should be the standard of care for those with good performance status and no hippocampal metastases. METHODS We conducted a prospective trial approved by the IRB (SMC0307-23), including patients aged 18 and above with primary brain tumors post-resection or biopsy. Exclusion criteria included multifocal glioma crossing to the other hemisphere. RT was delivered to a total dose of 60Gy in 30 fractions with concomitant TMZ. Diffusion tensor imaging (DTI) was performed to map hippocampal-associated white matter tracts. Memory fiber tracts and hippocampi were contoured and integrated into RT planning using Eclipse treatment planning software. Dosimetric analyses compared two plans: one with memory fiber constraints and one without. RESULTS Twelve patients with low-grade gliomas were included, with successful contouring of memory fibers and hippocampi. VMAT treatment plans met dose constraints for memory fibers, with an average mean dose of 10.1 Gy. The average MoCA score before RT was 27.1 and 26.4 at six months post-treatment, with a p-value of 0.07. Excluding one patient, the scores were 27.1 and 26.6, respectively (p=0.13). CONCLUSION MRI planning using DTI for memory fiber detection and incorporation into RT planning via VMAT techniques enables hippocampal and associated white fiber sparing, potentially preserving cognitive function. Preliminary cognitive data are promising, supporting the need for further validation in a larger cohort.

NIMG-10. THE ROLE OF FIBROBLAST ACTIVATION PROTEIN IN GLIOBLASTOMA AND GLIOSARCOMA – A COMPARISON OF TISSUE, 68GA-FAPI-46 POSITRON EMISSION TOMOGRAPHY AND SURVIVAL DATA

Abstract BACKGROUND Despite their unique histological features,gliosarcomas belong to the group of glioblastomas and are treated according to the same standards. Fibroblast-activation-protein(FAP) is a component of a tumor-specific subpopulation of fibroblasts that play a critical role in tumor growth and invasion.However,the prognostic impact of FAP in glioblastoma and gliosarcoma is unclear. METHODS In a retrospective analysis,patients diagnosed with glioblastoma without sarcomatous differentiation and gliosarcoma were enrolled.Histological examination was performed using immunohistochemical FAP-staining and quantitative analysis with a standardized FAP-score.In a subset of patients,FAPI46-PET has been performed.The SUV-values are planned to be correlated with FAP-expression in the tumor tissue.Data obtained from immunohistochemical analysis and SUV-values are planned to be brought into perspective with clinically relevant prognostic factors,including survival estimates. RESULTS We enrolled 61 patients,including 13 diagnosed with gliosarcoma.Our analysis revealed that gliosarcomas exhibit significantly higher FAP-expression (median FAP-score: 3) compared to glioblastomas without sarcomatous differentiation (median FAP-score: 0.5, p<0.0001),where FAP was predominantly observed in the perivascular space.In gliosarcomas,FAP was also expressed by neoplastic cells.Moreover,a significant relationship was established between the immunohistochemical FAP-scores and the SUVmean and SUVpeak values on PET,suggesting that the PET tracer uptake accurately reflects the tumor’s FAP-expression.However,the differential expression of FAP suggests its potential as both a diagnostic marker and a therapeutic target.This hypothesis is further supported by the application of 68Ga-FAPI-46-PET in a 66-year-old female patient with recurrent gliosarcoma,alongside immunohistochemical analysis of tumor tissue.Both methods identified elevated FAP-expression and uptake,underscoring the feasibility of FAP as a target for nuclear medicine therapies in brain tumors. CONCLUSIONS Our study establishes a significant correlation between SUVmean/SUVpeak in 68Ga-FAPI-46 PET scans and FAP-expression in glioblastoma.Gliosarcomas express significantly more FAP than other glioblastomas. These insights suggest FAP’s potential as a theranostic target.We plan to investigate the effectiveness of FAP-specific tracers in treating recurrent gliosarcoma,aiming to open new therapeutic avenues.

INNV-23. UNDERSTANDING THE BURDEN OF MIDH1/2 DIFFUSE GLIOMA AND THE COMPLEXITY OF NAVIGATING THE PATIENT PATHWAY: INSIGHTS FROM PATIENTS AND CAREGIVERS

Abstract Diffuse gliomas with mutations in isocitrate dehydrogenase 1 or 2 (mIDH1/2) are characterized by a slow-progressing yet life-limiting disease predominantly in young people. We report interim findings from a qualitative study to describe the mIDH1/2 diffuse glioma patient pathway, experience of the disease, and treatment approaches. Patients, caregivers, and patient-association group (PAG) representatives undertook individual interviews, with patients also completing standardized exercises as pre-work. Materials were developed in collaboration with the International Brain Tumour Alliance. Patients were aged ≥12 years with mIDH1/2 glioma and last resection ≥6 months before enrollment, either undergoing active observation or receiving chemotherapy/radiotherapy. Caregivers were living with the patient. PAG representatives were active members of a brain tumor PAG. From November 2023 to March 2024, 30 patients (Australia: n=10; China: n=6; France, UK: n=5 each; Canada, Japan: n=2 each), two caregivers (China, Australia: n=1 each) and one PAG (UK) participated. Median age of patients was 41.5 years, with 17 astrocytoma and 13 oligodendroglioma diagnoses. Presentation symptoms, circumstances of diagnosis and treatment, access to care, and navigation in the healthcare system differed per patient and within countries. Surgical resection was perceived as a crucial stage, both feared and desired. A second opinion was more often sought for surgery than for subsequent treatment approaches. Patients undergoing chemotherapy/radiotherapy (n=17) or active observation (n=13) expressed substantial physical, socioeconomic, financial, and psychological burden. Patients receiving active observation experienced strong and ongoing anxiety, as the uncertainty of tumor recurrence took a toll on their emotional wellbeing in the long term. The experience of people living with mIDH1/2 diffuse glioma is heterogeneous regarding their pathway and complexity navigating the healthcare system, with a substantial psychological and socioeconomic impact. Improved education, as well as facilitating early navigation and prioritizing shared decision-making along the disease pathway, will better support people living with mIDH1/2 diffuse glioma.