Metastatic Brain Tumors Research Articles

Abstract A019: Discovery of a potent and brain-penetrable tubulin inhibitor SB-216 that shows efficacy in primary tumor growth and brain metastasis

Abstract A major clinical challenge in cancer treatment is to prevent and treat metastatic disease. Despite the significant advancements in targeted therapy and immunotherapy, chemotherapeutic drugs, including taxanes, remain one of the mainline systemic treatment options for several major cancer types. However, the prolonged use of taxanes has been associated with the development of multidrug resistance, dose-limiting hematopoietic toxicity, and neurotoxicity, frequently presenting as persistent peripheral neuropathy. In addition, these drugs have limited blood-brain barrier penetration, and thus they are not effective in treating brain tumors or brain metastases from other cancer types, particularly breast cancer metastases. We have developed a new generation of tubulin inhibitors, termed colchicine binding site inhibitors (CBSIs). Unlike taxanes, these compounds bind to the colchicine site in tubulin, structurally less complex than taxanes which enables fine-tuning of physical-chemical properties, and shows the ability to overcome acquired drug resistance to existing taxane drugs. One of the best inhibitors in this class of compounds is SB-216. We have solved the high-resolution crystal structure of SB-216 in a complex with tubulin protein (PDB: 6X1F) and confirmed its mode of action. Extensive preclinical evaluations of SB-216 in a number of tumor models, including taxane-resistant prostate cancer, melanoma, ovarian cancer, and triple-negative breast cancer, indicated that SB-216 is highly potent in suppressing both primary tumor growth and tumor metastases. Importantly, SB-216 shows high brain penetration and shows efficacy in suppressing brain metastases from triple-negative breast cancer. SB-216 also has good drug-like properties and shows strong promise as a new generation of tubulin inhibitor for systemic cancer treatments, not only in brain metastasis from non-CNS tumors but also potentially be useful for brain tumors such as glioma. The work is supported by NIH/NCI grants R01CA14876 and R01CA276152 and the DoD grant HT9425-23-1-0216. Citation Format: Kelli L. Adeleye, Satyanarayana Pochampally, Raisa Krutilina, Rui Wang, Junming Yue, Tiffany Seagroves, Duane D.Miller, Wei Li. Discovery of a potent and brain-penetrable tubulin inhibitor SB-216 that shows efficacy in primary tumor growth and brain metastasis [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Optimizing Therapeutic Efficacy and Tolerability through Cancer Chemistry; 2024 Dec 9-11; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(12_Suppl):Abstract nr A019.

Imlunestrant is an Oral, Brain-Penetrant Selective Estrogen Receptor Degrader with Potent Antitumor Activity in ESR1 Wildtype and Mutant Breast Cancer.

Targeting of the estrogen receptor (ER) by anti-estrogens is the standard-of-care for patients with ER+ HER2- advanced/metastatic breast cancer. While anti-estrogens that degrade ERα (fulvestrant) or block estrogen production (aromatase inhibitors) have improved patient outcomes, clinically important challenges remain related to drug administration, limited bioavailability, lack of brain exposure, and acquired resistance due to ESR1 mutations. These limitations indicate a need for more robust ER-targeted therapies. Here, we discovered and characterized imlunestrant, a next-generation potent, brain-penetrant oral selective estrogen receptor degrader (SERD). Imlunestrant degraded ERα and decreased ERα-mediated gene expression both in vitro and in vivo. Cell proliferation and tumor growth in ESR1 wildtype and mutant models were significantly inhibited by imlunestrant. Combining imlunestrant with abemaciclib (CDK4/6 inhibitor), alpelisib (PI3K inhibitor), or everolimus (mTOR inhibitor) further enhanced tumor growth inhibition, regardless of ESR1 mutational status. In an ER+ breast cancer intracranial tumor model, imlunestrant prolonged survival compared to vehicle or alternative SERD therapies. Together, these finding support the potential of imlunestrant to degrade ERα and suppress the growth of ESR1 wildtype and mutant breast cancer, including brain metastatic tumors.

Intraoperative Real-Time Near-Infrared Image-Guided Surgery to Identify Necrotic Tissues.

The usefulness of intraoperative real-time fluorescence navigation using indocyanine green (ICG) for metastatic brain tumors, schwannomas, and meningiomas is well established. However, its application in cases of radiation-induced brain necrosis remains unexplored. Surgical intervention is performed in symptomatic and medically refractory cases; however, radiation-necrotic lesions often exhibit a diffuse pattern with unclear surgical boundaries, making it challenging for surgeons to identify the lesion during the surgery. Four patients with intracranial necrotic tissues received 1.5 mg/kg ICG 1 hour before observation during the surgery. We used near-infrared fluorescence to identify the necrotic location. Case 1: A 61-year-old man with lung cancer and metastatic brain tumor history exhibited left-sided weakness a year after craniotomy and radiotherapy. A new lesion required surgery, where ICG fluorescence imaging highlighted a significant contrast in the resection cavity, aiding in successful lesion removal without complications. Case 2: A 51-year-old man with resected glioblastoma developed paralysis. ICG fluorescence during surgery confirmed necrosis and enabled the lesion's removal despite potential inaccuracies due to brain shift, without ICG-related complications. Near-infrared fluorescence could visualize necrotic tissues in all 4 cases. The mean signal-to-background ratio of the necrotic tissues in delayed window ICG was 3.5 ± 0.7. The ratio of the gadolinium-enhanced T1 tumor signal to the brain (T1-weighted background ratio) was 2.3 ± 0.4. This report is the first to demonstrate the efficacy of ICG intraoperative fluorescence imaging in identifying radiation-induced necrotic brain tissues.

Increased mTOR activity and RICTOR copy number in small cell lung carcinoma progression

Small cell lung carcinoma (SCLC) is a highly malignant cancer with early metastatic dissemination and poor clinical outcomes. Mutations in the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway, including the frequently occurring rapamycin-insensitive protein (RICTOR) amplification, have been described in these tumours. Moreover, the associated mTOR hyperactivity could be exploited for personalised treatment. Our aim was to study mTOR activity, RICTOR amplification, and their role during SCLC progression. In situ mTOR activity and Rictor expression were characterised by immunohistochemistry in 50 primary and 50 brain metastatic tumours, and 14 paired SCLC patient samples. RICTOR copy number changes were analysed by fluorescence in situ hybridisation of the paired SCLC patient samples and in vivo experiments. Additionally, in vitro sensitivity to cisplatin and mTOR inhibitors was evaluated in SCLC cell lines harbouring RICTOR amplification and other mTOR pathway mutations. High Rictor expression and mTOR complex 2 (mTORC2) hyperactivity were significantly associated with brain metastases and worse overall survival. An increase in RICTOR copy number was observed in paired samples during progression. The importance of these alterations was confirmed both by the sensitising effect of vistusertib in vitro and the RICTOR copy number/expression changes in xenografts. Our study highlights the role of mTORC2 in SCLC progression. Early detection of RICTOR amplification in primary tumours and targeting mTORC2 in these cases may represent a promising novel strategy to develop personalised therapy for metastasis prevention.

Abstract A002: Dissecting the brain metastatic microenvironment to uncover immune and molecular correlates of response to immunotherapy

Abstract Despite promising results with immune checkpoint blockade (ICB) therapy, brain metastases (BrM) remain a deadly complication for cancer patients. Understanding the highly specialized brain metastatic tumor microenvironment (BrTME) is crucial for identifying determinants of response, however, progress has been hindered by limited access to patient samples and scarcity of relevant preclinical models. Here, we developed two mouse melanoma BrM models by intracardiac injection of cells derived from our previously established M4-B2905 melanoma mouse cell line. We characterized their mutational landscape and performed single-cell phenotypic and transcriptomic analysis, demonstrating that these models recapitulate the cellular and molecular features of human melanoma BrMs. Comparative and interactome analysis of our models revealed key factors contributing to ICB response and resistance. We found that the responsive model (BR1) was characterized by tumor cells that polarize microglia toward reactive states via inflammatory programs and response to IFN signaling. These microglia express high levels of antigen presentation and immunostimulatory molecules, triggering T cell recruitment and activation and promoting ICB therapy response. In contrast, in the resistant model (BR3), the tumor cells express neurological molecular signatures and ligands that sustain microglia homeostasis. This results in poor T cell infiltration predominantly composed of naïve cells, evading immune reaction and promoting ICB resistance. While we showed that systemic ICB therapy induced BrTME changes in both models, differences between responder and resistant models were maintained, emphasizing the importance of tumor cell-intrinsic programs in dictating the BrTME. We validated the translational relevance of our findings and demonstrated that BR1 signatures positively correlate with T cell infiltration and are associated with improved patient outcomes, whereas BR3 signatures negatively correlate with T cells and are found in patients with worse prognosis. Here we address an important challenge in the field by providing clinically relevant BrM models that recapitulate both the cellular and molecular features of human disease and the variability of ICB response seen in patients. We further reveal mechanistic insights into BrM ICB response and identify potential therapeutic targets to modulate the BrTME. Citation Format: Amelie Daugherty-Lopes, Eva Perez-Guijarro, Vishaka Gopalan, Jessica Rappaport, Quanyi Chen, April Huang, Khiem C. Lam, Sung Chin, Jessica Ebersole, Emily Wu, Gabriel Needle, Isabella Church, George Kyriakopoulos, Shaojun Xie, Yongmei Zaho, Charli Gruen, Antonella Sassano, Romina E Araya, Andres Thorkelsson, Cari Smith, Maxwell P. Lee, Sridhar Hannenhalli, Chi-Ping Day, Glenn Merlino, Romina S. Goldszmid, Shaojun Xie. Dissecting the brain metastatic microenvironment to uncover immune and molecular correlates of response to immunotherapy [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr A002.

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.

SURG-07. QUANTIFYING THE RISK OF SHORT TERM SEIZURES FOLLOWING LASER INTERSTITIAL THERMAL THERAPY

Abstract BACKGROUND Tumor-related epilepsy is a common sequela of both primary and metastatic brain tumors, as well as radiation necrosis (RN). Laser interstitial thermal therapy (LITT) is an effective option for lesional cytoreduction but induces transient peritumoral edema that typically resolves within 3 months of the procedure. Accordingly, we quantified the risk of seizure development early post-LITT in patients with tumors or RN of diverse histologies. METHODS Patients treated with LITT for brain tumors or radiation necrosis at a high-volume center from 2015 – 2021 with at least 3 months of clinical follow-up were evaluated for seizure risk and time to discontinuation of anti-epileptic drugs (AEDs) for at least 4 weeks, with censoring at death or last follow-up. RESULTS One-hundred and seventeen patients met inclusion criteria, and 22 (19%) experienced a post-LITT seizure within 3 months of surgery. Those with pre-LITT seizures (P = 0.03), prior whole-brain radiation (WBRT) (P = 0.0099), or lower pre-operative KPS (P = 0.04) were more likely to have a post-LITT seizure. Frontal lobe tumors appeared to be more frequently associated with seizures (68% vs 45%, P = 0.06). Prior WBRT, odds ratio (OR) 4.27 (95% CI 1.01 – 18.55), P = 0.047 and pre-LITT seizure, OR 5.39 (95% CI 1.87 – 16.31), P = 0.002 remained predictive on multivariate analyses. Successful AED weaning occurred at a median of 1.68 months (no seizure within 3-months group) versus undefined for patients experiencing seizures (P = 0.015). Post-LITT seizures within 3 months were associated with worsened post-LITT overall survival, 5.95 vs 17.2 months, P < 0.0001. DISCUSSION Prior seizure history or previous WBRT pose a risk of breakthrough seizures following laser ablation. Neurosurgeons should consider extended AED treatment or referral for management of tumor-related epilepsy in patients with these neurologic risk factors.

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.

BIOM-28. WHOLE EXOME TUMOR MOLECULAR PROFILING FROM CEREBROSPINAL FLUID (CSF): PRELIMINARY RESULTS OF A PILOT STUDY

Abstract BACKGROUND Tissue sampling for molecular profiling has become an integral part of the diagnosis, prognosis, and management of CNS malignancies. However, many tumors are surgically inaccessible, and even biopsy of accessible lesions conveys some risk, and the possibility of sampling error. We evaluated the accuracy and potential utility of CSF liquid biopsy for identifying mutations in patients with intracranial tumors. METHODS CSF samples were collected from ventricular reservoirs and stored at -80 degrees Celsius until analyzed. Cell-free nucleic acids were extracted, concentrated, and quantified. Samples over 110ng quantification were normalized to 110ng and input into library prep. Library prep was done using v3.5 of Caris Assure and whole exome sequencing in an S2 FC on a Novaseq 6000. Bioinformatic analysis was performed. RESULTS CSF samples were obtained from 20 patients (10 gliomas, 5 CNS lymphomas, 5 metastases), 19 of whom also had tumor specimens available. Two hundred eighty-one mutations were identified: 17 (6.6%) in tumor only, 184 (72.4%) in CSF only, and 80 (31.5%) in both. Key alterations found in CSF include: IDH, TERT, ATRX in gliomas, and MYD88, PIM1, BCL2, TERT in lymphomas. Glioma CSF with IDH1 mutations did not have PTEN mutations (with one exception, in which the CSF was collected 3 years after the tissue). Targetable mutations in metastases included PIK3CA, NF1, and BRCA. CONCLUSION These preliminary results suggest that CSF liquid biopsy may be useful for identifying mutations in primary and metastatic brain tumors. Serial sampling is feasible, and may disclose changes in diagnostic and/or driver mutations over time, with important therapeutic and diagnostic implications. Many mutations were found in CSF alone. CSF may capture the entire molecular landscape of the tumor, overcoming the sampling error inherent in tissue biopsies. Prospective studies are underway to further elucidate the clinical applications of this technique.

TMIC-10. GENETIC LANDSCAPE OF BRAIN METASTASIS IN TRIPLE-NEGATIVE-BREAST CANCER: COMPARISON OF PAIRED PRIMARY AND METASTATIC TUMOR USING SPATIAL TRANSCRIPTOMIC ANALYSIS

Abstract The survival rate of individuals diagnosed with breast cancer has shown improvement over time, primarily attributed to advancements in early detection methods and the implementation of proactive treatment strategies. However, it is concerning that the incidence of breast cancer continues to rise, thereby leading to a corresponding increase in mortality rates among female breast cancer patients. Among these, the presence of brain metastasis is associated with a worse prognosis in individuals with breast cancer. Notably, triple-negative breast cancer exhibits a heightened propensity for the development of brain metastasis. Furthermore, there has been a notable rise in the duration of breast cancer survival, leading to a concomitant increase in the occurrence of metastatic cancer throughout the course of the disease. Presently, a greater number of patients are experiencing brain metastases, surpassing the figures reported in current statistical data. In instances of metastatic cancer, a distinct microenvironment that is particular to the tumor is formed in a distant location. The comprehension of the molecular genetic and immunological mechanisms involved in the several phases of brain metastasis, including tumor cell invasion, engraftment, and proliferation, has significant importance in the context of patient treatment and prognosis prediction. However, it is worth noting that a well-defined scientific foundation in this area is currently absent. The objective of this study was to analyze the molecular genetic characteristics of triple-negative breast cancer primary tumors and brain metastasis tumors. This was achieved by utilizing spatial transcriptome analysis technology to compare the differences in genetic profiles between the tumor cells and the surrounding tumor microenvironment. The findings of this study allowed for a comprehensive comparison of the tumor microenvironment at each site. In order to validate alterations in gene expression of various constituents and elucidate the mechanisms behind metastasis, it is imperative to conduct spatial confirmation.

STEM-09. A GROUP 3 MEDULLOBLASTOMA STEM CELL PROGRAM IS MAINTAINED BY OTX2-MEDIATED ALTERNATIVE SPLICING

Abstract Group 3 medulloblastomas (MBs) are highly metastatic pediatric brain tumors with limited therapeutic options. The transcription factor orthodenticle homeobox 2 (OTX2) is a known driver and molecular hallmark of Group 3 MB. We previously demonstrated that OTX2 regulates Group 3 MB cell fate decisions that favor self-renewal or stemness and the retention of a primitive cerebellar rhombic lip signature. Here, we show that OTX2-regulated alternative splicing (AS) is a major driver of Group 3 MB progression. Surprisingly, the functional role of post-transcriptional events, such as AS, in Group 3 MB development has never been explored. This gene regulatory layer represents an untapped source of therapeutic targets. Using a combination of TurboID, RNA-sequencing and single cell RNA-seq, we characterized the Group 3 primary MB AS landscape with a focus on genes that control MB stem cells. OTX2 associates with the multimeric Large Assembly of Splicing Regulators (LASR) complex through protein-protein interactions and can directly or indirectly bind RNA. Together, OTX2 and LASR complex proteins oversee a pro-tumorigenic splicing program that is mirrored in the human cerebellar rhombic lip origins and is associated with Group 3γ MBs that exhibit the worst prognosis. Among our core set of OTX2-regulated spliced genes, periphilin 1 (PPHLN1) is expressed in the most primitive cerebellar rhombic lip stem cells, and mimicking PPHLN1 AS by pre-treating cells with a splice blocking antisense morpholino reduces tumor growth while increasing survival in vivo. We propose that OTX2-mediated AS is a key determinant of cell fate decisions favoring the maintenance of the stem cell state. Targeting transcription factors like OTX2 is notoriously difficult; thus, our work offers fresh opportunities to exploit MB-specific AS events therapeutically to abrogate tumor progression.

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.

ANGI-04. DISTINCT EXPRESSION OF TARGET MOLECULES BETWEEN TUMOR CELLS IN CEREBROSPINAL FLUID AND LEPTOMENINGES FOR LEPTOMENINGEAL METASTASIS

Abstract PURPOSE Metastatic brain tumor frequently present with leptomeningeal metastasis. The leptomeningeal metastasis is usually diagnosed by cerebrospinal fluid (CSF) cytology and/or contrast enhanced magnetic resonance imaging. However, it remains to be known whether tumor cells from CSF faithfully represent the tumor cells of leptomeniges. Therefore, this study aimed to clarify the transcriptome differences between tumor cells from cerebrospinal fluid, and spinal cords METHODS MDA-MB-231 cells labeled with GFP and luciferase were injected into the right ventricle of immunodeficient mice. Tumor cells from cerebrospinal fluid, and spinal cords were sorted and analyzed the transcriptome differences by RNA sequencing, RESULTS RNA sequencing analysis showed distinct transcriptome profiles between tumor cells from cerebrospinal fluid and spinal cord. Genes related to ECM receptor interaction and PI3K-Akt signaling pathway such as COL1A1, COL1A2, THBS1 were significantly highly upregulated in tumor cells from spinal cord compared to those from CSF CONCLUSIONS Tumor cells from spinal cord had different characteristics in transcriptome from those from CSF. Different therapeutic strategies might be needed to regulate tumor cells from spinal cord and those from CSF.

CNSC-06. NAVIGATING BRAIN CANCER: PATIENT STORIES AND MEDICAL BREAKTHROUGH

Abstract The complex interplay of genetic mutation, dys regulated signalling pathways, Epigenetic modifications and Interaction with tumor microenvironment are the major aggravating factors for Brain Tumors. Neurological complications involve Increased Intracranial pressure, Seizures, Motor and Sensory deficits, Aphasia, Hydrocephaly, Behavioral and personality changes, Cerebellar Symptoms. It is diagnosed in a sequential steps. Collecting good history from patient in primary then examining the patient all through and making some investigations to come to a final diagnosis. On asking history to a patient he complains of recurrent convulsions, Personality changes and some motor activity deficit and loss of few senses. On examination we can reveal defect in cranial nerve functions, Motor or sensory deficits, loss of reflexes and coordination. Then Investigations being the next step for diagnosis, We ask the patient to undergo for a test for Blood Biomarkers and CSF analysis in case of suspection of metastatic Brain tumors. Biopsy to obtain for Histopathological Examination. Histopathological examination is done for analysis of genetic mutations and molecular markers. The other imaging techniques like MRI, MRS, CT, PET, EEG are done. This gives a clear picture of what actually caused tumor and shows a way for treatment. Now the treatment involves both Medical and Surgical treatment. Medical treatment includes Chemotherapy along with radiation therapy where the drugs given are Temozolomide and targeted therapy included EGFR BRAF inhibitors for glioblastoma and low grade gliomas respectively. Tumor treating fields- Optune is given. Surgical treatment involves Craniotomy for removal of primary Brain tumors, Neuro Endoscopy if tumor is present in ventricles or base of Brain, Laser interstitial Thermal therapy for deap seated and recurrent brain tumors. This is all about the treatment and now the patient management is very important for further clinical help. Physical, occupational and speech therapy helps patients recover. Symptomatic approach for inoperable tumors Provide comprehensive support for patients nearing end of life, Emphasise confidence and Quality of life.

EPID-11. RATES OF CRANIOTOMIES FOR BRAIN METASTASES AFTER INTRODUCTION OF IMMUNOTHERAPY

Abstract Immunotherapy has revolutionized the treatment paradigm for patients with brain metastases and has been found to prolong overall survival. We sought to determine whether rates of craniotomies for the treatment of brain metastases has decreased since the introduction of immunotherapy into routine treatment regimens. Pathology records were queried at our institution from 2011-2022 to include all patients surgically treated for brain metastases. A total of 885 samples from 789 unique patients were analyzed. National data was queried from the NSQIP database from 2011-2022 to include patients surgically treated for brain metastases with a total of 14,494 cases. A Craniotomy for Metastases Index (CMI) was generated to reflect the total number of craniotomies performed over time. The most common institutional primary cancers were lung (46.1%), breast (17.4%), and gastrointestinal (10.1%), with the most common lung cancers being adenocarcinoma (57.11%) and non-small cell carcinoma (11.52%). The institutional CMI demonstrated a non-significant decrease in the number of craniotomies (R2=0.0545, p=0.46) across all time ranges, as well as no significant change in CMI when comparing rates from 2011-2016 and 2017-2022 (p=0.37). The national CMI demonstrated a significantly positive slope of 0.03 (R2=0.544, p=0.006), as well as a significant increase (p=0.005) in craniotomies when comparing rates from 2011-2016 and 2017-2022. Despite the growing use and efficacy of immunotherapy in the treatment of brain metastases and increasing overall survival, the rates of craniotomies had no change institutionally and increased nationally. Several reasons for these findings may include: longer overall survival of patients with systemic cancer can lead to the development of metastatic brain tumors later in their disease course, improvement of surgical techniques making resection safer, and variable response of patients to stereotactic radiosurgery (SRS). Further studies should be conducted to determine the effect of SRS on these findings. Surgical resection remains the mainstay in the treatment of brain metastases.

TMIC-12. LITT RESULTS IN ROBUST T CELL INFILTRATION WITHIN THE TUMOR MICROENVIRONMENT IN A BRAIN METASTASIS MURINE MODEL

Abstract INTRODUCTION Laser interstitial thermal therapy (LITT) is a novel minimally invasive neurosurgical technique used to ablate intra-axial brain tumors with real-time thermometry. The impact of LITT on the brain metastatic tumor microenvironment (TME) is unknown in patients due to limitations of tumor tissue collection post-LITT. The primary objective of this study was to describe the kinetics of immunologic infiltration within the TME in a melanoma brain metastasis model. METHOD: C57BL6 mice underwent intra-cranial implantation of B16F10-OVA tumor cells and treated with LITT using a custom-made murine LITT system developed in our laboratory. The tumors were treated to 42°C (near infra-red 1064 nm DPSS laser system) 7 days post-surgery. Tumors were collected 2 days and 10 days post-LITT for immune-phenotyping using flow cytometry. Blood was collected 6 h and 48 h post-LITT to perform the ELISA for IFN-g and TNF-a. RESULTS LITT treatment triggered a cascade of local infiltration of immune cells at different time points. 2-days post-LITT resulted in increased CD8 T cells (p<0.05), macrophage (p<0.05) and microglia infiltration (p<0.01) within the TME compared to control and sham surgery animals. By 10 days after LITT, significant infiltration by CD8 T cells (p<0.0001) and M1 macrophages (p<0.0001) was observed. The CD8 T cells were T central memory (TCM) and T effector memory (TEM). Moreover, comparison between 2 days and 10 days after LITT revealed significant increase of TEM (p<0.0001) and TCM (p<0.001) 10 days post-LITT. In an ELISA assay, non-significant differences were observed in IFN-g and TNF-a level at 48 h. CONCLUSIONS LITT enhances the recruitment of cytotoxic CD8 T cells within TME in a time-dependent manner. The ability of LITT to recruit TCM and TEM to the TME strongly support its potential therapeutic benefit, especially in the context of immunotherapy.

Immunotherapeutic and Targeted Strategies for Managing Brain Metastases from Common Cancer Origins: A State-of-the-Art Review.

This review examines contemporary strategies for managing brain metastases (BM) from common cancers such as lung, breast, and melanoma. We evaluate the efficacy and applicability of targeted therapies and immunotherapies, exploring their potential to cross the blood-brain barrier and improve patient outcomes. Recent studies have shown that tyrosine kinase inhibitors, immune checkpoint inhibitors, and ADCs effectively treat BM. These treatments can overcome the challenges posed by the blood-brain barrier and improve therapeutic outcomes. ADCs are promising because they can deliver cytotoxic agents directly to tumor cells, which reduces systemic toxicity and increases drug delivery efficiency to the brain. Personalized medicine is becoming increasingly significant in treatment decisions, with biomarkers playing an essential role. Advances in molecular genetics and drug development have led to more refined treatments, emphasizing the precision medicine framework. The management of BM is evolving, driven by drug efficacy, resistance mechanisms, and the need for personalized medicine. Integrating ADCs into treatment regimens represents a significant advancement in targeting metastatic brain tumors. Despite these advances, BM management still presents considerable challenges, requiring ongoing research and multi-institutional trials to optimize therapeutic strategies. This review outlines the current state and future directions in treating BM, highlighting the critical need for continued innovation and comprehensive clinical evaluations to improve survival rates and quality of life for affected patients.

Detection of brain metastases from blood using Brain nanoMET sensor: Extracellular vesicles as a dynamic marker for metastatic brain tumors

Brain metastases account for a significant number of cancer-related deaths with poor prognosis and limited treatment options. Current diagnostic methods have limitations in resolution, sensitivity, inability to differentiate between primary and metastatic brain tumors, and invasiveness. Liquid biopsy is a promising non-invasive alternative; however, current approaches have shown limited efficacy for diagnosing brain metastases due to biomarker instability and low levels of detectable tumor-specific biomarkers. This study introduces an innovative liquid biopsy technique using extracellular vesicles (EVs) as a biomarker for brain metastases, employing the Brain nanoMET sensor. The sensor was fabricated through an ultrashort femtosecond laser ablation process and provides excellent surface-enhanced Raman Scattering functionality. We developed an in vitro model of metastatic tumors to understand the tumor microenvironment and secretomes influencing brain metastases from breast and lung cancers. Molecular profiling of EVs derived from brain-seeking metastatic tumors revealed unique, brain-specific signatures, which were also validated in the peripheral circulation of brain metastasis patients. Compared to primary brain tumor EVs, we also observed an upregulation of PD-L1 marker in the metastatic EVs. A machine learning model trained on these EV molecular profiles achieved 97% sensitivity in differentiating metastatic brain cancer from primary brain cancer, with 94% accuracy in predicting the primary tissue of origin for breast metastasis and 100% accuracy for lung metastasis. The results from this pilot validation suggest that this technique holds significant potential for improving metastasis diagnosis and targeted treatment strategies for brain metastases, addressing a critical unmet need in neuro-oncology.

Distinguishing clinical and imaging characteristics of primary central nervous system lymphoma from high-grade glioma and metastatic brain tumors.

The purpose of this retrospective analysis was to evaluate the clinical presentations, radiological characteristics, patient outcomes, and therapeutic approaches among individuals diagnosed with primary central nervous system lymphoma (PCNSL), high-grade glioma (HGG), and metastatic brain tumors (METS). We assembled a cohort of brain tumor patients from two medical centers, with two oncologists independently reviewing their clinical profiles. A retrospective examination of 87 PCNSL, 87 HGG, and 71 METS cases was performed to assess the aforementioned parameters. Notable variations were identified in the incidence of epileptic seizures and cognitive impairments between PCNSL and METS patients. Cerebral hemisphere involvement was predominantly observed in HGG and METS cases. PCNSL cases exhibited a higher likelihood of multiple lesions, whereas HGG showed a greater tendency for recurrence. The median survival times were established at 24.3months for PCNSL, 44.5months for HGG, and 27.1months for METS patients. In PCNSL cases, the number of lesions was identified as a significant predictor of mortality (P = 0.008). Our findings highlight the importance of clinical and imaging features in diagnosing PCNSL, which may present distinct features compared to HGG and METS.

ACSS2 regulates ferroptosis in an E2F1-dependent manner in breast cancer brain metastatic cells.

Brain metastasis diagnosis in breast cancer patients is considered an end-stage event. The median survival after diagnosis is measured in months, thus there is an urgent need to develop novel treatment strategies. Breast cancers that metastasize to the brain must adapt to the unique brain environment and are highly dependent on acetate metabolism for growth and survival. However, the signaling pathways that regulate survival in breast cancer brain metastatic (BCBM) tumors are not known. Primary brain tumor cells can convert acetate to acetyl-CoA via phosphorylation of acetyl-CoA synthetase 2 (ACSS2) by the cyclin-dependent kinase-5 (CDK5) regulated by the nutrient sensor O-GlcNAc transferase (OGT). Here, we show that breast cancer cells selected to metastasize to the brain contain increased levels of O-GlcNAc, OGT and ACSS2-Ser267 phosphorylation compared to parental breast cancer cells. Moreover, OGT and CDK5 are required for breast cancer cell growth in the brain parenchyma in vivo. Importantly, ACSS2 and ACSS2-S267D phospho-mimetic mutant are critical for in vivo breast cancer growth in the brain but not in the mammary fat pad. Mechanistically, we show that ACSS2 regulates BCBM cell survival by suppressing ferroptosis via regulation of E2F1-mediated expression of anti-ferroptotic proteins SLC7A11 and GPX4. Lastly, we show treatment with a novel brain-permeable small molecule ACSS2 inhibitor induced ferroptosis and reduced BCBM growth ex vivo and in vivo. These results suggest a crucial role for ACSS2 in protecting from ferroptosis in breast cancer brain metastatic cells and suggests that breast cancer brain metastatic cells may be susceptible to ferroptotic inducers.