Tumor Treatment Research Articles

RBIO-02. DEVELOPMENT OF FLASH-CAR RADIOIMMUNOTHERAPY FOR PEDIATRIC BRAIN TUMORS

Abstract Pediatric brain tumors including medulloblastoma and high-grade glioma are generally refractory to T cell-based immunotherapy, largely due to an immune-hostile microenvironment infiltrated extensively with immunosuppressive macrophages. Ultra-high dose rate (FLASH) radiotherapy holds promise for treating solid tumors, given the potential lower toxicity in normal tissues and possible favorable impact on tumor immunity. Using a genetically engineered mouse model of medulloblastoma and glioma, we show that FLASH radiation stimulates pro-inflammatory polarization in tumor macrophages. Single-cell transcriptome analysis shows that FLASH proton beam radiation skews macrophages towards proinflammatory phenotypes and increases T cell infiltration in the medulloblastoma model. Further bulk transcriptome analyses reveal that FLASH radiation reduces peroxisome proliferator-activated receptor (PPAR)-γ and arginase-1 expression and inhibits immunosuppressive macrophage polarization under stimulus-inducible conditions. Mechanistically, FLASH radiation abrogates lipid oxidase expression and oxidized low-density lipid (oxLDL) generation to reduce PPARγ activity, while standard radiation induces reactive oxygen species (ROS)-dependent PPARγ activation in macrophages. Notably, FLASH radiotherapy improves infiltration and activation of chimeric antigen receptor (CAR) T cells and sensitizes tumors to GD2 CAR T immunotherapy in the autochthonous medulloblastoma and syngeneic glioma models. These findings suggest that FLASH radiotherapy may reprogram macrophage lipid metabolism to reverse tumor immunosuppression and that combination FLASH-CAR radioimmunotherapy may offer exciting opportunities for treatment of pediatric brain tumor.

Optic disc and peripapillary tumors

Abstract This review covers the tumors either originating or seen close to the optic disc in the peripapillary area. Most of the optic disc tumors are diagnosed on clinical examination. In a few atypical cases, ancillary imaging, such as optical coherence tomography, fluorescein angiography, and ultrasonography, may be required to demonstrate characteristic features. The majority of these tumors have systemic associations, and hence, a multidisciplinary approach involving ocular oncologists, neurophysicians, radiation oncologists, and medical oncologists is the need of the hour. The treatment of optic disc tumor is challenging due to its proximity to critical areas such as optic nerve and macula, which could be a limiting step when compared to conventional treatments such as laser photocoagulation and surgical excision.

TMET-07. RADIORESISTANT GLIOBLASTOMA EVADES MITOCHONDRIAL LIPOTOXICITY THROUGH ALTERED DGKB AND DGAT1

Abstract Glioblastoma (GBM) is the most common and aggressive primary brain tumor, with a median survival of only 15 months despite multimodal therapy. Radiotherapy is a conventional therapy of GBM treatment, but the development of radioresistance often leads to tumor recurrence and treatment failure. To elucidate the molecular mechanisms underlying radioresistance in GBM, we established radioresistant GBM cell lines through repeated exposure to ionizing radiation. Transcriptomic analysis revealed that diacylglycerol kinase beta (DGKB), an enzyme that converts diacylglycerol (DAG) to phosphatidic acid, was significantly downregulated in radioresistant GBM cells. Functional studies demonstrated that knockdown of DGKB or expression of a kinase-dead DGKB mutant resulted in DAG accumulation and reduced fatty acid oxidation. Conversely, overexpression of DGKB activated fatty acid oxidation, increased reactive oxygen species (ROS) production, and sensitized GBM cells to radiation. Interestingly, we found that radiation upregulated the expression of diacylglycerol acyltransferase 1 (DGAT1), which catalyzes the conversion of DAG to triglycerides. Knockdown of DGAT1 using shRNA or miR-3918 mimic reduced lipid droplet formation and enhanced radiosensitivity both in vitro and in vivo. Furthermore, using Connectivity Map, we identified cladribine as a potential radiosensitizing agent that increases DGKB and decreases DGAT1. Cladribine effectively sensitized GBM cells to radiation and significantly prolonged the survival of mice bearing GBM xenografts. In conclusion, our study reveals a novel mechanism by which radioresistant GBM cells maintain lipid homeostasis through downregulation of DGKB and upregulation of DGAT1 to evade lethal mitochondrial lipotoxicity. Targeting the DGKB-DGAT1 axis represents a promising therapeutic strategy to overcome radioresistance and improve the outcomes of GBM patients.

PATH-50. AI-POWERED AUTOMATED TISSUE SEGMENTATION IMPROVES OUTCOME STRATIFICATION IN GLIOBLASTOMA

Abstract Glioblastoma displays morphological heterogeneity on routine H&E whole slide images, with conflicting evidence on the reliability of morphological features in predicting tumor behavior and treatment response. However, current standards for assessing morphology and disease status rely on nonquantitative manual evaluation by pathologists, which are prone to inherent variation. We sought to (1) expand the tools available for quantitative assessment and (2) evaluate the utility of this approach in identifying valuable biomarkers. We trained a deep learning-based algorithm using DenseNet on HALO AI platform for automated segmentation of six tissue classes (heavy infiltration, mild infiltration, mesenchymal tissue, geographic necrosis, palisading necrosis, and hemorrhage) on 3232 labeled annotations from 100 whole slide images. Manual pathologists’ estimations from clinical records showed strong correlation with corresponding digital quantifications (p<0.001), and further pixel-wise validation on 828 separate annotations showed high overlap between predicted and ground truth segmentations (precision=0.88, recall= 0.85, F1-score=0.87). We then identified a longitudinal cohort of 115 newly diagnosed glioblastoma tissue paired with the recurrence post-treatment (RT/TMZ), including all 827 H&E whole slide images scanned at 40x. The quantification of longitudinally paired tissue showed a relative increase in geographic necrosis (+62%) and mild infiltration (+110%) and a relative decrease in palisading necrosis (-54%) and heavy infiltration (-35%) between the two timepoints. Patients with rapid clinical progression had more areas of large geographic necrosis (p=0.002), and mesenchymal tissue increase was associated with worse overall survival (p=0.016). Digitally quantified heavy infiltration as a predominant tissue on recurrence outperformed corresponding pathologist estimation of tumor as a predominant tissue on recurrence in stratifying overall-survival (p=0.005 vs p=0.640). Collectively, our AI-powered classifier enables an automated objective quantification of glioblastoma tissue, identifies markers of clinical response, and offers a potential adjunct to enhance routine pathologic reporting of glioblastoma.

STEM-08. LIPID SATURATION HOMEOSTASIS PRESENTS A TARGETABLE VULNERABILITY IN MYC-AMPLIFIED GROUP 3 MEDULLOBLASTOMA

Abstract Medulloblastoma (MB) is the most common malignant pediatric brain cancer, originating from the cerebellum. Despite advancements in standard of care (SoC), MB remains fatal for 30% of patients. Tumor relapse, spinal metastasis and treatment resistance are the most prevalent in MYC-driven Group 3 MB (G3-MB). Patients surviving SoC are faced with life-long neurocognitive and neurodevelopmental deficits. These issues highlight the urgent need for improved treatment modalities. Reprogramming of cellular lipid metabolism is an emerging hallmark of cancer and may yield novel cancer-specific therapeutic options. Here we explore the lipidome of both G3-MB and its proposed cell of origin, human neural stem cells (hNSCs) by comparing untargeted lipidomics using Liquid-Chromatography-Mass Spectrometry (LC-MS). Comparative analyses revealed a differential abundance of distinct lipid species in G3-MB, with an overall reduced saturation level of fatty acids (FAs). These findings implicate the de novo lipid synthesis (DNL) pathway. We identified the enzymes involved in DNL to be essential for MB survival in our genome-wide CRISPR KO screen. Additionally, mRNA expression of the DNL enzymes increases at relapse in our SoC-adapted murine patient-derived xenograft (PDX) model. Pharmacological and genetic targeting of the DNL enzyme Stearoyl-CoA Desaturase 1 (SCD1) selectively targets G3-MB. Furthermore, small molecule treatment of SCD1 demonstrates efficacy against G3-MB PDX models in vivo. We identified SCD expression as a prognostic marker in Group 3 and 4 MB patients and identified possible pathways for MB treatment. Overall, these findings indicate that SCD1 is a potent target for the treatment of G3-MB.

EPCO-48. RESOLVING INTRATUMORAL TRANSCRIPTIONAL HETEROGENEITY ACROSS THE CORE-EDGE SPATIAL AXIS IN GLIOBLASTOMA

Abstract Intratumoral heterogeneity promotes tumor progression, treatment resistance, and recurrence in glioblastoma (GBM), and the cellular tumor core and infiltrating edge represent transcriptionally distinct cellular ecosystems. In this study, we characterize and validate the molecular differences across the core-edge spatial axis in GBM by applying whole-transcriptome GeoMx Digital Spatial Profiling (DSP) to 5 IDH-wildtype tumors. Three 3-micron tissue cores were extracted from each tumor and arranged into a tissue microarray (TMA). Core and edge regions of interest (ROIs) were chosen through coregistration of H&E and immunofluorescent TMA scans. Following DSP, data for 44 ROIs (30 core and 14 edge) and 8530 RNA targets were bioinformatically analyzed. Single-sample gene set enrichment analysis aligned the DSP core and edge regional signatures to those of publicly annotated datasets, substantiating our profiling methodology. Unsupervised analyses revealed ROI clusters unique to each tumor specimen for both pre- and post-normalized data. To mitigate a potential patient-level effect in subsequent differential gene expression and pathway analyses, we leveraged a linear mixed-effect model using core versus edge as a fixed effect and tumor specimen as a random effect. Our analyses showed upregulation of epigenomic markers in core ROIs and neuronal markers in edge ROIs. Further, core and edge signatures were incongruent with the canonical GBM subtypes (Mesenchymal, Classical, Proneural) and malignant cell states (OPC-like, NPC-like, AC-like, MES-like). Cellular deconvolution analysis highlighted differential enrichment of neoplastic cells in core ROIs and neuroglia (astrocytes and oligodendrocytes) in edge ROIs. In summary, we leverage spatial profiling to further validate the geographic molecular heterogeneity of GBM, which is characterized by divergent neuronal programs within the infiltrating edge.

QOL-28. CANCER-RELATED DISTRESS IN NEURO-ONCOLOGY: PATIENTS INFORM PROGRAM DEVELOPMENT FOR ENHANCING QUALITY OF LIFE

Abstract BACKGROUND Brain tumor diagnosis and treatment result in significant negative sequelae, including cognitive decline, fatigue, and psychosocial symptoms. This study aimed to identify brain tumor patients’ sources of cancer-related distress and examine their interest in various treatment modalities targeting cognitive decline to inform program development for this underserved population. METHODS In pursuit of program development, patients with both primary and secondary brain tumors completed an anonymous survey. They reported demographics, tumor characteristics, subjective cognitive functioning; and, rated sources of cancer-related symptom distress (i.e., cognitive changes, fatigue, physical symptoms, motor functioning, balance, mood, and relationship) and interest in treatments targeting cancer-related cognitive decline (i.e., cognitive rehabilitation, mindfulness-based practices, psychotherapy, and medication). Descriptive statistics, t-tests, chi-square, and linear regressions were conducted. RESULTS Among participants (N=137, Mage=49.6±15.8, 58.1% female, 84.8% White), 50.4% endorsed subjective cognitive functioning below the mean (MFACT-Br-CI=22.6±7.5). Nearly half reported significant distress due to cancer-related fatigue (49.6%) and cognitive change (48.9%). Patients’ mean severity of distress due to cognitive decline was significantly greater relative to all other cancer-related symptoms (ps<.001), except fatigue (p>.05). Age, gender, or time since diagnosis were not significant predictors (ps>.05) of distress due to cognitive decline. Most patients with distress due to cognitive change were interested in cognitive rehabilitation (63.6%) and mindfulness-based practices (61.6%), and only 40.4% were interested in medication. Interest in cognitive rehabilitation was not predicted by symptom distress, subjective cognitive functioning, age, gender, or time since diagnosis (ps>.05). Gender was the only significant predictor of interest in mindful movement (b=.18, p=.041), with greater interest among women (χ2(1)=4.65, p=.031). CONCLUSIONS Fatigue and cognitive decline were the most distressing cancer-related symptoms for neuro-oncology patients. These findings emphasize the need for integrated interventions, including cognitive rehabilitation and mindfulness, as well as multi-targeted and individualized treatments for fatigue and cognitive decline in neuro-oncology.

DNAR-16. TARGETING APOBEC CYTIDINE DEAMINASES TO ENHANCE RADIOSENSITIVITY IN GLIOMA

Abstract Glioma is the most common and aggressive primary adult brain tumor. Radiation therapy (RT) is a critical part of glioma treatment, but radioresistance severely limits its therapeutic efficacy. To better understand how radioresistance develops, we analyzed 212 paired primary and recurrent gliomas from the Glioma Longitudinal Analysis Consortium. We found a significant increase in mutational signatures associated with the activity of the Apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC) family of cytidine deaminases in RT-treated recurrent gliomas (p<0.001, paired Wilcoxon signed-rank test). Further analysis of post-treatment mutations showed that RT increased APOBEC mutational signatures independent of other factors (p<0.001, multivariable log-linear regression), suggesting that APOBEC proteins become activated by radiation. However, their role in promoting tumor evolution and treatment resistance is currently unknown. Further analyses of extended signature contexts and expression data nominated APOBEC3B (A3B) and APOBEC3G (A3G) as candidates for creating these mutational signatures. To investigate their roles in RT response, we knocked out (KO) A3B and A3G individually in patient-derived glioma cell lines before RT. Compared to Control cells, irradiated A3B-KO and A3G-KO cells acquired significantly fewer APOBEC mutational signatures by whole genome sequencing (p<0.05, Kruskal–Wallis test) and exhibited enhanced radiosensitivity in vitro. Interestingly, the KO cells displayed a significant decrease in mutational signatures associated with Non-Homologous End-Joining (NHEJ), one of the main pathways for repairing the RT-induced DNA damage (p<0.05, Kruskal–Wallis test), suggesting that APOBEC deletion impaired DNA repair. This was further supported by persistent gH2AX DNA damage foci 48h post-RT and reduced autophosphorylation of DNA-dependent protein kinase (DNA-PK), a vital component of the NHEJ pathway, particularly in A3G KO cells. Overall, our results identify APOBEC proteins as potential targets for radiosensitizing gliomas and highlight the clinical utility of using mutational signatures to predict and monitor response to treatment.

Local Endoscopic Treatment of Low-Grade Urothelial Tumors in the Upper Urinary Tract—Oncological Outcome of a Consecutive Single-Center Series of 118 Patients

Background: Upper urinary tract urothelial tumors are mostly treated with the use of endoscopic laser ablation. The treatment is recommended when the tumor is low grade and non-invasive. Objective: The aim of the present study was to investigate the oncological outcome of patients treated endoscopically for low-grade (LG) upper tract urothelial carcinoma (UTUC). Methods: One hundred and eighteen consecutive patients with pTa LG UTUC initially treated with laser ablation from 2012–2022 at a single university hospital were included. Patient and tumor characteristics, treatment, and oncological outcomes were retrospectively registered from electronic medical journals. Survival analysis was performed using Kaplan–Meier and Nelson–Aalen plots. Results: The median number of local recurrences was 2 with a median time to first recurrence of 5 months (IQR: 2–46). The 2-year share of patients having no recurrence was 28.8%. The risk of recurrence was highest within the first 3 years following initial treatment. Two-year survival function with no progression and preserved renal unit was 67.9%. The two-year overall survival (OS) and disease-specific survival (DSS) were 84.2% and 97.1%. The 5-year OS and DSS were 59.1% and 94.1%. The median follow-up time for OS was 36 months (IQR: 20.3–58.8). Conclusions: In the patient series, we found that the risk of recurrence following laser ablation of LG UTUC was high; however, it was associated with a low risk of progression and high OS and DSS. Therefore, we conclude that treatment with laser ablation in patients with LG UTUC is safe, although frequent follow-up is needed to detect recurrence.

NIMG-72. VOXEL-WISE, MULTIVARIABLE, COX PROPORTIONAL HAZARD STATISTICAL PARAMETER MAPPING TO INVESTIGATE THE INTERPLAY BETWEEN TUMOR LOCATION, PROGNOSTIC VARIABLES, AND EXPERIMENTAL TREATMENT IN A PHASE 3 TRIAL OF NEWLY-DIAGNOSED GLIOBLASTOMA TREATED WITH CHEMORADIATION WITH OR WITHOUT BEVACIZUMAB

Abstract BACKGROUND Tumor location is known to impact overall survival (OS) in glioblastoma. However, there is a lack of quantitative tools for studying the interplay between tumor location, prognostic variables, and treatments. In the current study we develop a voxel-wise statistical parameter mapping technique using a multivariable Cox regression model to describe the influence of tumor location on treatment effects in newly diagnosed glioblastoma. METHODS 598 newly diagnosed glioblastoma patients from the phase 3 AVAglio trial were studied. Areas of T2/FLAIR hyperintensity and resection cavities on post-surgical MRI scans were segmented and aligned to MNI atlas space. Voxel-wise Cox proportional hazards models for OS were run for each image voxel and included tumor presence in a specific voxel, age, MGMT promoter methylation, baseline tumor volume, and treatment (chemoradiation with or without bevacizumab). Results. After adjusting for other variables, tumor location was an independent predictor of favorable OS for tumors with involvement in the right prefrontal cortex (p<0.05, HR ranging ~0.48–0.65) and a predictor of shorter OS for tumors in the left mesial/basal temporo-occipital areas (p<0.05, HR ~3–6.2) and in the left hemisplenium of the corpus callosum (p<0.05, HR ~2.5–3). Baseline tumor volume (HR ~4–6 x10-6), MGMT status (HR ~0.38–0.41), and age (HR ~1.020–1.025) were significative predictors regardless of location (p<0.05 in all locations). Interestingly, chemoradiation plus bevacizumab treatment showed a favorable OS compared with chemoradiation alone for tumors with involvement in the right corticospinal tract, right motor and sensory cortices, and left hemisplenium of the corpus callosum (p<0.05, HR ~0.82). CONCLUSIONS Tumor involvement in the prefrontal cortex is associated with favorable prognosis, while tumors in mesial/basal temporo-occipital areas or splenium of the corpus callosum are associated with shorter OS. Chemoradiation plus bevacizumab may improve OS for tumors involving eloquent motor areas and the corticospinal tract.

PATH-29. LONGITUDINAL EPIGENOMIC EVOLUTION OF IDH-WILDTYPE GLIOBLASTOMA

Abstract Glioblastoma, IDH-wildtype remains a molecularly heterogeneous disease that is refractory to current therapies. To investigate how longitudinal epigenomic evolution of glioblastoma drives tumor progression and treatment resistance, we performed comprehensive histopathologic assessment, targeted genomic sequencing, and genome-wide DNA methylation profiling of paired initial and recurrent IDH-wildtype glioblastoma samples from 98 patients, as well as a separate longitudinal cohort of IDH-mutant astrocytomas for comparison. Primary treatment-naïve IDH-wildtype glioblastomas had more globally hypomethylated genomes compared to primary IDH-mutant astrocytomas. At time of recurrence, IDH-mutant astrocytomas uniformly became more hypomethylated similar to the global methylation levels in IDH-wildtype glioblastomas. In contrast, recurrent IDH-wildtype glioblastomas were heterogeneous with subsets becoming more globally hypermethylated (27%), hypomethylated (22%), or remaining stable (51%). Accordingly, a substantial proportion (52%) of recurrent glioblastomas underwent methylation class switching compared to their matched primary tumor, with a predominance of the RTK2 epigenetic subtype at initial surgery and the Mesenchymal epigenetic subtype at recurrence. Among approximately 850,000 interrogated CpG sites, we identified only 110 and 153 sites that consistently became more hypermethylated or hypomethylated between initial and recurrent IDH-wildtype glioblastomas, which regulate genes involved in neuronal morphogenesis, oligodendrocyte differentiation, and myelination. In contrast, we identified 260 and 18,527 CpG sites that consistently became more hypermethylated or hypomethylated between initial and recurrent IDH-mutant astrocytomas, which regulate genes involved in neuronal stem-like differentiation, cell cycle control, and other biologic processes. Finally, we developed a DNA methylation evolution signature incorporating change in mean beta-methylation values from initial to recurrent tumor specimens across 347 critical CpG sites that significantly correlated with clinical outcomes for patients with IDH-wildtype glioblastoma. In summary, IDH-wildtype glioblastomas demonstrate heterogeneous epigenomic evolution patterns distinct from IDH-mutant astrocytomas. These changes in epigenetic patterns may identify unique subgroups of glioblastoma with differential treatment response and inform future therapeutic studies targeting differentially methylated gene programs.

NIMG-01. RADIOMIC DATA ANALYSIS WITH ENSEMBLE MACHINE LEARNING TECHNIQUES PREDICT GRADE, HISTOPATHOLOGIC SUBTYPE, AND 1P/19Q CO-DELETION STATUS IN PATIENTS WITH LOW-GRADE GLIOMAS

Abstract Low-grade gliomas (LGGs) are a diverse group of primary brain tumors characterized by their variable prognosis and treatment response. Traditionally, the management of LGGs has relied on histopathological analysis, which sometimes offers limited insight into tumor behavior and treatment outcomes. Recent advances in radiomics have enabled the extraction of detailed quantitative features from routine imaging, providing a non-invasive method to assess tumor characteristics. These radiomic features can capture underlying tumor heterogeneity more comprehensively than conventional methods. Integrating radiomic data with ensemble machine learning techniques offers a promising approach to enhance the prediction of tumor grade, histopathologic subtype, and genetic alterations such as 1p/19q co-deletion status in LGGs, potentially leading to more tailored therapeutic strategies. We combined radiomic-genomic data from 159 magnetic resonance imaging (MRI) scans from the updated LGG-1p19qDeletion dataset (Erickson 2020) and 114 MRI scans from the ReMIND dataset (Juvekar 2024). Expert radiologists performed segmentations. A total of 2446 extracted radiomic features were initially extracted. Feature selection was performed using wrapper- and filter-based techniques with cross-validation. Prediction models were built using machine learning techniques, including random forest and extreme gradient boosting. Using Random Forest, we achieved high accuracy in predicting histopathologic subtype (88.14%, AUC 96.68%) with precision of 87.86% and Dice score of 87.88%. For grade prediction (accuracy 76.19%, AUC 91.84%), precision was 73.91%, and the Dice score was 77.27%. For 1p/19q co-deletion status (accuracy 75.61%, AUC 82.74%), precision was 77.78%, and the Dice score was 73.68%. Our study establishes a robust radiomic workflow to predict tumor grade, histopathologic subtype, and 1p/19q co-deletion status in low-grade gliomas, enhancing diagnostic accuracy and treatment personalization. This methodology can be applied clinically to improve the stratification of treatment plans for low-grade gliomas, potentially leading to effective, personalized therapy options. Using multicentric data potentially improved external validity, something which past research lacked. Future research should focus on validating and deploying this model using observational multicentric study designs.

RADT-05. VASCULAR OVERLAP PROVIDES PROTECTION FROM GAMMA-KNIFE-INDUCED RADIATION NECROSIS IN A METASTATIC BRAIN TUMOR COHORT

Abstract INTRODUCTION Radiation necrosis (RN) is a long-term complication of Gamma-Knife (GK) Radiosurgery, an established treatment for metastatic brain tumors. Few dosimetric parameters have shown to predict RN, including tumor target volume, treatment dose, and V12 Gy (volume of normal brain receiving 12 Gy). Vascularity has yet to be explored as an independent predictor of RN. OBJECTIVE To evaluate the role of vascular overlap in GK-induced RN. METHODS All metastatic brain tumor patients treated with GK between 2014-2019 were retrospectively screened for post-treatment radiographic RN. Vascular overlap, defined by the MCA-ACA and MCA-PCA border regions, was determined by two blinded neurosurgeons and one radiation oncologist. Multivariate logistic regression analysis was performed to determine factors predictive of RN using variables determined significant by univariate analysis and clinical relevance. Covariates included V12 as a binary variable (≥8 vs. <8 cm3), vascular overlap, supratentorial location, and eloquent location. RESULTS 6% (20/321) of all metastatic brain tumor patients developed RN and were included for analysis, with the final cohort being 60% (12/20) female with a mean age of 59 years, comprising 77 lesions. V12 (≥8 cm3) showed a significant increase in risk of developing RN [OR = 8.18; (coef, 95% CI: 2.10 (0.49, 3.72), p=0.011)]. Conversely, vascular overlap showed a protective effect against RN [OR = 0.23 (-1.49 (-2.79, -0.19), p=0.024)], with a lower rate of RN in areas of vascular overlap (10%) than non-vascular overlap (26%). Neither supratentorial location [OR = 3.31 (1.20 (-0.76, 3.16), p=0.231)] nor location within eloquent brain [OR = 0.96 (-0.04 (-1.48, 1.39), p=0.95)] showed significance. CONCLUSION For the first time, we show that patients with metastatic brain lesions in anatomical regions of vascular overlap treated with GK are less likely to develop RN. Future work should validate these findings with the goal of optimizing radiation dosing to mitigate RN incidence and recurrence rates.

CTNI-83. PROPOSAL FOR A PILOT PHASE 1B CLINICAL TRIAL WITH ADDITION OF NATURAL MARINE PRODUCT FUCOIDAN TO ANTI-NEOPLASTIC THERAPY FOR PATIENTS WITH RECURRENT GLIOBLASTOMA (RGBM) TO IMPROVE FATIGUE AND OTHER HEALTH-RELATED QUALITY OF LIFE (HRQOL) SYMPTOMS

Abstract BACKGROUND Recurrent Glioblastoma (rGBM) has poor outcome with limited treatment options. rGBM causes significant fatigue and other health-related quality of life (HRQOL) symptoms secondary to tumor progression and anti-neoplastic therapies. More than 80% of brain tumor patients were found to experience fatigue during anti-neoplastic therapy and the incidence of cancer related fatigue may reach 89-94% among patients with rGBM. Therefore, improvement of fatigue and HRQOL in rGBM patients are crucial. Marine natural product, fucoidan, available as health supplement in the US, was found to play important roles in oncological management as supportive therapy against cancer and chemoradiation-related adverse effects and as a potential anti-neoplastic therapy. Fucoidan is a seaweed-derived sulfated polysaccharide. Data resulted from randomized clinical trials for colon, head and neck, and lung cancer patients suggest that fucoidan can improve cancer and chemotherapy or chemoradiation therapy related negative symptoms. In addition, Tachikawa et al. reported >50% tumor regression and increased natural killer (NK) cell activity in sarcoma-transplanted mice treated with Fucoidan. In Vitro anticancer investigation found that Fucoidan fractions clearly suppressed the growth of GBM U-251MG cancer cells. Multiple studies have also shown that fucoidan is tolerable with a good safety profile. METHOD 18 rGBM patients will be enrolled. Fucoidan based product will be administered orally at established dose for cancer patients daily with anti-neoplastic therapy over 6 months. Patients will be evaluated monthly for AEs and HRQOL score; laboratory and brain MRI monitoring will be performed per SOC guidelines. NK cell activity will be measured. POTENTIAL OUTCOME Fucoidan is safe and has good tolerability in combination with anti-neoplastic therapy for rGBM and improves fatigue and other HRQOL symptoms by ameliorating tumor progression and treatment related negative impact. Fucoidan may also improve survival in rGBM patients by improving the tolerability of anti-tumor therapy, augmenting cytotoxic effects, and inhibiting angiogenesis.

Magnetic resonance imaging techniques for monitoring glioma response to chemoradiotherapy.

Treatment response assessment for gliomas currently uses changes in tumour size as measured with T1- and T2-weighted MRI. However, changes in tumour size may occur many weeks after therapy completion and are confounded by radiation treatment effects. Advanced MRI techniques sensitive to tumour physiology may provide complementary information to evaluate tumour response at early timepoints during therapy. The objective of this review is to provide a summary of the history and current knowledge regarding advanced MRI techniques for early treatment response evaluation in glioma. The literature survey included perfusion MRI, diffusion-weighted imaging, quantitative magnetization transfer imaging, and chemical exchange transfer MRI. Select articles spanning the history of each technique as applied to treatment response evaluation in glioma were chosen. This report is a narrative review, not formally systematic. Chemical exchange saturation transfer imaging potentially offers the earliest method to detect tumour response due to changes in metabolism. Diffusion-weighted imaging is sensitive to changes in tumour cellularity later during radiotherapy and is prognostic for progression-free and overall survival. Substantial evidence suggests that perfusion MRI can differentiate between tumour recurrence and treatment effect, but consensus regarding acquisition, processing, and interpretation is still lacking. Magnetization transfer imaging shows promise for detecting subtle white matter damage which could indicate tumour invasion, but more research in this area is needed. Advanced MRI techniques show potential for early treatment response assessment, but each technique alone lacks specificity. Multiparametric imaging may be necessary to aid biological interpretation and enable treatment guidance.

RADT-24. WALLERIAN DEGENERATION OF THE CORTICOSPINAL TRACT IN GLIOMAS: A RETROSPECTIVE ANALYSIS AND A SYSTEMATIC REVIEW OF MOTOR FUNCTION IN ELOQUENT AREAS POST-RADIATION THERAPY. HOW IMPORTANT IS MOTOR FUNCTION FOR PATIENTS WITH GLIOMAS IN RADIATION THERAPY?

Abstract BACKGROUND The quality of life for patients with gliomas is significantly impacted by tumor characteristics, treatment modalities, and radiation dosages. Variability in radiotherapy protocols and differences in tissue tolerance necessitate a detailed risk-benefit assessment, especially in eloquent brain areas responsible for motor functions. METHODS A retrospective analysis of electronic medical records from a Brazilian Radiation Therapy Department (2018-2023) was conducted. Patients with gliomas who underwent surgical resection and adjuvant radiochemotherapy, subsequently developing Wallerian Degeneration of the Corticospinal Tract (WDCT), were included. Additionally, a systematic search was performed in PubMed, Embase, and Cochrane databases, focusing on radiotherapy in eloquent areas and evaluating motor function. Of the 1,064 studies identified, 11 underwent full-text review by two independent examiners. RESULTS Among 192 glioma patients, 13 (6.77%) developed WDCT, all with high-grade gliomas, including 3 post-reirradiation cases. Retrospective dosimetric analysis of the corticospinal tract was performed for two patients who had tractography. Patient 1, with right frontoparietal tumor, had an ipsilateral corticospinal tract volume of 10.6 cm³, a max dose of 62.81 Gy, and 0.5 cc receiving 62.2 Gy; the contralateral tract volume was 18.5 cm³, with 0.5 cc receiving 51 Gy. Patient 2, with right frontal tumor, had an ipsilateral corticospinal tract volume of 31.1 cm³, a max dose of 42.76 Gy, and 0.5 cc receiving 42.37 Gy; the contralateral tract volume was 30.3 cm³, with 0.5 cc receiving 24.19 Gy. The systematic review identified 5 studies reporting pre- and post-radiotherapy motor outcomes in eloquent areas, with 4 focusing exclusively on gliomas. However, heterogeneity in radiotherapy techniques and outcome assessments precluded a meta-analysis. CONCLUSION Motor function in glioma patients undergoing radiation therapy remains an underexplored area. Future studies should focus on standardized assessments of functional outcomes to establish dose constraints and optimize treatment protocols, thus improving the quality of life for glioma patients.

EPCO-54. MULTIOMIC ANALYSIS OF SPINAL EPENDYMOMAS REVEALS MECHANISMS OF TUMOR AGGRESSIVENESS WITH MYCN AMPLIFICATION

Abstract Grade-3 spinal ependymomas, particularly those harboring MYCN amplification, have dismal prognoses despite optimal treatment regimens. MYCN functions as a transcription factor (TF) to drive the expression of key tumor driver genes. Our aim is to identify mechanisms underlying tumor aggressiveness and treatment resistance in MYCN-amplified ependymomas. MYCN amplification in spinal ependymomas was identified with custom next generation sequencing panels and bulk methylation analysis. We then conducted paired single-nucleus RNA (snRNA-seq) and chromatin accessibility (snATAC-seq) sequencing of grade-2 (n=2, 1 patient) and grade-3 spinal ependymomas (n=6, 6 patients, 4 MYCN-amplified). Comparator snRNA-seq datasets (grade-2/grade-3; 8/2) were included from a publicly available dataset (GSE163686; all non-MYCN-amplified). Canonical cell classes were identified with a combination of cluster- and cell-based strategies. Downstream analysis was conducted using R 4.3 (Seurat, Signac, clusterProfiler, CellChat), and Python 3.11 (scanpy) packages. We identified ependymoma tumor cells distinct from canonical immune cell classes with gene expression analysis and confirmed a distinct copy-number-variation pattern in these cells with chromosome 1 and 2p gain, and chromosome 6p and 22q loss. MYCN-amplified tumor cells (compared to non-MYCN-amplified grade2/3 tumor cells) showed increased differential accessibility at genes including VEGFA. Increased MYCN TF activity was confirmed with gene overexpression of downstream targets including NOTCH3, CREB5, PLK1, and VEGFA. Other genes that were highly accessible and overexpressed in MYCN-amplified tumor cells were related to oxidative stress, differentiation, and anti-apoptotic pathways. MYCN-amplified tumor cells modified the tumor microenvironment with increased VISTA signaling between MYCN-amplified tumor cells and tumor-associated macrophages, creating an immunosuppressive environment. We confirmed these effects by observing a higher proportion of M2-like macrophages in MYCN-amplified tumors (29.6% vs 18.2%). In conclusion, MYCN amplification in spinal ependymomas upregulates tumor cell proliferation, angiogenesis, and M2-like macrophage recruitment/programming.

PATH-54. HIGH-THROUGHPUT SINGLE NUCLEAR DNA SEQUENCING OF HUMAN SPORADICNF1 MUTANT IDH-WILDTYPE GLIOBLASTOMAS REVEALS PATTERNS OF TUMOR EVOLUTION AND RECURRENCE

Abstract The advent of single cell techniques has advanced our understanding of glioblastoma (GBM) evolution and cell lineage relationships. However, study of mutational co-occurrence and clonal phylogeny has been hampered by limitations in single cell genotyping. Here, we perform semi-automated, rapid single nuclear dissociation followed by targeted single nucleus DNA sequencing (snDNA-seq) of eleven retrospectively identified somatic NF1 mutant IDH-wildtype glioblastomas. Bulk DNA sequencing was performed as part of routine clinical care using a CLIA-certified targeted sequencing panel. For snDNA-seq, tissue cores with greater than 30% tumor were dissociated on a S2 genomics S100 Singulator followed by snDNA-seq using a targeted 361 amplicon panel (Tapestri, Mission Bio, USA) to sequence for recurrently observed single nucleotide substitutions and copy number alterations. A mean of 3,661 cells were recovered per sample with a mean of 96 reads per cell per amplicon and 87% mean panel uniformity. SnDNA-seq validated point mutations and copy number alterations observed in bulk DNA-sequencing and revealed novel alterations and subclonal copy number alterations not detected on bulk analysis. Within individual samples, snDNA-seq based phylogenetic reconstruction identified mutually exclusive patterns of mutation between NF1 and PI3K signaling alterations, suggesting these events may occur in distinct tumor subclones. With regard to copy number alterations (CNAs), snDNA-seq demonstrated intra-tumoral heterogeneity for chromosome 9p loss, chromosome 7 gain, and chromosome 10 monosomy. Subclonal CNA clones not detected by bulk sequencing were identified in 5 samples. Analysis of a matched primary-recurrent tumor pair revealed expansion of a specific mutational clone (loss of 9p, 10p, gains of 1p, 7, 15, and 19q) at recurrence. SnDNA-seq recapitulated bulk DNA sequencing alterations and identified distinct patterns of mutational co-occurrence, CNAs, and tumor evolution over time. Reconstructing GBM phylogeny at single cell resolution has potential translational implications for understanding tumor evolution and treatment resistance.

EXTH-28. DEVELOPING A NOVEL INJECTABLE IMMUNOTHERAPEUTIC GEL FOR ENCAPSULATION OF NATURAL KILLER CELLS FOR POST-SURGICAL GLIOBLASTOMA TREATMENT

Abstract Malignant brain tumors are one of the leading causes of death among all cancers. Approximately 40,000 people are diagnosed with malignant brain tumors every year. Among these patients, 15,000 cases are glioblastoma (GBM) with a very poor prognosis; even after aggressive surgical resection and adjuvant chemo/radiotherapy, the median survival is only 14.6 months. The major reason for poor prognosis is the blood-brain barrier, which prevents therapeutic agents from reaching the target area. Therefore, there are only a few choices of drugs available for brain tumor treatment. To date, temozolomide (TMZ) and the Gliadel wafer have been clinically used as standard chemotherapy agents after brain tumor resection. However, drug resistance to TMZ and the poor drug diffusion rate of the Gliadel wafer still result in ineffective suppression of residual cancer cells. To overcome the above-mentioned difficulties in clinical brain tumor treatment, in situ self-crosslinking multifunctional hydrogels was developed to carry natural killer cells (NK cells) and radiosensitizers as a novel brain tumor treatment system. Unlike traditional hydrogels catalyzed by pH value or temperature, this new system is stable and consistent as an immune cell carrier. We used fibrinogen, thrombin, and alginic acid as the backbone of the in situ self-crosslinking hydrogel, tested the properties of the synthesized hydrogel, and analyzed the gel-formation time and swelling rate. The release rate of NK cells was also examined. In a brain tumor animal model, the use of hydrogel-NK cells significantly inhibited tumor proliferation and prolonged animal survival time. In conclusion, this therapeutic hydrogel carrying NK cells can serve as a novel post-operation adjuvant therapeutic tool for malignant brain tumors.

QOL-20. NATIONAL BRAIN TUMOR SOCIETY BRAIN TUMOR QUALITY OF LIFE RESEARCH AGENDA

Abstract BACKGROUND QoL is a critical aspect of health care outcomes, particularly in the context of brain tumor treatment and survivorship. There are evidence gaps in optimal strategies for improving QoL among brain tumor patients and care partners. Understanding the multifaceted dimensions of QoL and identifying key areas for brain tumor QoL research can significantly enhance patient care and support. Engaging the brain tumor community in defining QoL outcomes and determining research priorities can help orient research resources to community needs and perspectives. OBJECTIVE To summarize the process and outcomes of an NBTS-led collaborative effort to co-design a comprehensive research agenda on QoL for brain tumor patients and care partners, as outlined in the “Brain Tumor QoL Research Agenda.” METHODS The agenda was developed through a collaborative effort involving experts in neuro-oncology, patients, care partners, patient advocacy groups, and healthcare professionals over a two-year period. A review of existing literature, patient experiences, and expert opinions informed the identification of key research priorities. A multistakeholder advisory group held monthly meetings where brain tumor QoL was defined. In 2023, we conducted two “Research Roundtables” for adults and pediatric/AYA. The World Cafe method captured data and a survey consensus process to validate findings. RESULTS The QoL research agenda delineates a multifaceted framework encompassing domains crucial for understanding and improving QoL in brain tumor patients. Key focus areas include symptom management, psychosocial support, care burden, treatment decision-making, survivorship issues, and health care delivery models. An RFP was released by NBTS with input from stakeholder advisors in April 2024. CONCLUSION The Brain Tumor QoL Research Agenda created a roadmap for advancing research efforts aimed at enhancing the QoL of individuals affected by brain tumors. By addressing the identified research priorities, healthcare stakeholders can work towards implementing effective interventions and policies to optimize patient outcomes and well-being. This program was funded through a Patient-Centered Outcomes Research Institute® (PCORI®) Eugene Washington PCORI Engagement Award (EACB-23261).