Focal Radiation Research Articles

Abstract IA13: Preliminary results of a multicentric, prospective randomized trial testing focal radiotherapy and immunotherapy in HR+ breast cancer patients

Abstract Radiation (RT) is a potent immune modulator, since it harnesses both the innate and adaptive components of the immune system (reviewed in Galluzzi et al NRCO, 2023:20:543-557). The promising immunological impacts of RT inspired a clinical trial in HR+ BC conducted as part of a level 3 breakthrough award (BC180595), partnering P.I.s Drs. S. Formenti and S. Demaria.The trial was designed to evaluate the therapeutic impact of RT in combination with immunotherapies (PD1 and FLT-3 Ligand), applied preoperatively, during neoadjuvant aromatase inhibition. The trial tested the role of increasing cross-presentation by using FLT-3 Ligand and overcoming immune resistance by targeting the PD1 pathway. All patients received focal radiothepy to the imaged primary tumor (8Gyx3, total dose 24 Gy) while receiving letrozole (as standard endocrine therapy), preoperatively. Patients were randomly assigned to 4 arms : ARM1 - Letrozole (2.5 mgm PO qDay) and Radiation to the tumor (8Gy x 3); ARM 2 - Letrozole and Radiation to the tumor followed by Pembrolizumab, started after radiation, q3 weeks for a total of 5 doses; ARM 3 - Letrozole and Radiation to the tumor preceded by Flt3 ligand (75 microgram/kg/ day, s.c. for 5 consecutive days), and ARM 4 Letrozole and Radiation to the tumor preceded by Flt3 ligand and followed by Pembrolizumab (doses as above). The endpoint for the trial is pathological response defined by residual cancer burden (RCB score), a pathological assessment method predictive of survival outcomes (https://doi.org/10.1186/s12885-023-11719-z). For this trial "responders" were considered patients with tumor achieving RCB response of 0 or 1. Because of the randomized design with a control arm of patients receiveng letrazole and focal RT only, the study enables to learn how the additional immunotherapies affect pathological response of RT + letrozole . Pathological response from the 17/27 accrued patients that had surgery are: for arm 1 = 33% (1/3), for arm 2 = 100% (3/3), for arm 3 = 12% (2/6) and for arm 4 = 20% (1/5). The trial utilizes a 3-stage design, by analyzing data when 6 patients with RCB response are available in each arm, before increasing accruals to that arm, with a Bayesian optimal phase II design (BOP2) ( Zhou, H., et al , 2017,Statistics in Medicine, 36: 3302-3314). This design has a power of 82% with a type I error rate controlled at 0.1. The trial continues accrual, with parallel immunomonitoring analysis of circulating biomarkers of response as well as spatial transcriptomics analysis on pretreatment biopsies, post RT and surgical tissues for each patient, to generate fundamental data on mechanisms of immune response in HR+ breast cancer treated with the different combinations tested. Preliminary information on the translational studies will be presented. Citation Format: Silvia C. Formenti. Preliminary results of a multicentric, prospective randomized trial testing focal radiotherapy and immunotherapy in HR+ breast cancer patients. [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Translating Targeted Therapies in Combination with Radiotherapy; 2025 Jan 26-29; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(2_Suppl):Abstract nr IA13

Insights into age-related osteoporosis from senescence-based preclinical models and human accelerated aging paradigms.

Preclinical models of age-related osteoporosis have been developed based on the accumulation and clearance of senescent cells. The former include animal models based on telomere dysfunction and focal radiation; the latter based on genetic and pharmacological targeting (i.e., removal) of senescent cells. The weight of evidence using these models suggests that cellular senescence plays a key role in the pathophysiology of aging-onset bone loss with the senescence-associated secretory phenotype (SASP) mediating local and systemic deleterious effects on the skeleton. Mitochondrial dysfunction has also been implicated in senescence and age-related comorbidities, including osteoporosis, and knock-in mutations in the mtDNA polymerase gamma (Polg) gene in mice may recapitulate similar respiratory chain complex defects in aged individual with osteoporosis. This and other contributions to senile osteoporosis may also be identified by the careful evaluation of non-genetic paradigms of human accelerated aging. Premature aging syndromes, especially those with a prominent bone loss phenotype, include clinical scenarios of skeletal unloading, premature ovarian failure and survival from childhood cancers. These non-hereditary progeroid syndromes implicate the involvement of lineage switching to an adipogenic fate, inhibition of Wnt signaling, increased osteoclastogenesis and activation frequency of osteoclasts, as well as the substantial burden of senescent cell accumulation.

Primary intracranial extraosseous Ewing's sarcoma with intraspinal metastasis in children: illustrative case.

The diagnosis of intracranial extraosseous Ewing's sarcoma (EES) poses challenges due to the absence of specific clinical and imaging features prior to surgery. It is crucial to differentiate the tumor from other small round cell malignancies postoperatively. A 7-year-old patient was admitted to the authors' hospital due to the in situ recurrence of a posterior fossa tumor more than 1 month after the initial surgery for headache. Subsequently, a second surgery was performed at the authors' hospital, and pathological analysis indicated medulloblastoma. Genetic testing indicated Ewing's sarcoma. After 16 cycles of chemotherapy and 8 weeks of focal radiotherapy, the patient continued to exhibit clinical and radiographic remission. Whole-spine magnetic resonance imaging (MRI) revealed intraspinal enhancing lesions, which extended throughout the entire spinal canal. Palliative treatment was administered. The patient has been under observation for 2 months thus far, demonstrating disease stability as a result of the palliative treatment. Primary intracranial EES is an exceptionally rare condition that can be easily misdiagnosed. Genetic testing is necessary to differentiate it from other small round cell tumors. Currently, a combination of surgery and chemoradiotherapy has proven to be an effective treatment approach. Postoperative follow-up should include MRI examination of the entire nervous system to detect any cerebrospinal fluid seeding metastasis and reduce mortality. https://thejns.org/doi/10.3171/CASE24488.

A non-purine inhibitor of xanthine oxidoreductase mitigates adenosine triphosphate degradation under hypoxic conditions in mouse brain.

The brain is an organ that consumes a substantial amount of oxygen, and a reduction in oxygen concentration can rapidly lead to significant and irreversible brain injury. The progression of brain injury during hypoxia involves the depletion of intracellular adenosine triphosphate (ATP) due to decreased oxidative phosphorylation in the inner mitochondrial membrane. Allopurinol is a purine analog inhibitor of xanthine oxidoreductase that protects against hypoxic/ischemic brain injury; however, its underlying mechanism of action remains unclear. In addition, febuxostat is a non-purine xanthine oxidoreductase inhibitor with a different inhibitory mechanism from allopurinol. The impact of febuxostat on brain injury has not been well investigated. Therefore, this study aimed to examine brain ATP and its catabolite levels in the presence or absence of allopurinol and febuxostat under hypoxic conditions by inactivating brain metabolism using focal microwave irradiation. The hypoxic treatment caused a decrease in the adenylate energy charge and ATP levels and an increase in its catabolic products in mouse brains. The febuxostat group showed higher energy charge and ATP levels and lower ATP catabolites than the control group. Notably, despite the comparable suppression of uric acid production in both inhibitor groups, allopurinol treatment was less effective than febuxostat. These results suggest that febuxostat effectively prevents hypoxia-induced ATP degradation in the brain and that its effect is more potent than allopurinol. This study will contribute to developing therapies for improving hypoxia-induced brain dysfunction.

Clinical implementation of RTT-only CBCT-guided online adaptive focal radiotherapy for bladder cancer

PurposeThe study assesses the clinical implementation of radiation therapist (RTT)-only Conebeam CT (CBCT)-guided online adaptive focal radiotherapy (oART) for bladder cancer, by describing the training program, analyzing the workflow and monitoring patient experience. Materials and methodsBladder cancer patients underwent treatment (20 sessions) on a ring-based linac (Ethos, Varian, a Siemens Healthineers Company, USA). Commencing April 2021, 14 patients were treated by RTTs supervised by the Radiation Oncologist (RO) and Medical Physics Expert (MPE) in a multidisciplinary workflow. From March 2022, 14 patients were treated solely by RTTs. RTT training included target delineation lessons and practicing oART in a simulation environment. We analyzed the efficiency of the RTT-only workflow regarding session time, adjustments by RTTs, attendance of the RO and MPE at the linac, and qualitative assessment of gross tumor volume (GTV) delineation. Patient experience was monitored through questionnaires. ResultsA training program resulted in a skilled team of RTTs, ROs and MPEs.The RTT-only workflow demonstrated shorter session times compared to the multidisciplinary approach. Among 14 patients treated using the RTT-only workflow, RTTs adjusted 99% of bladder volumes and 44% of GTV. 79% of the sessions proceeded without MPEs and ROs. All GTV delineations were RO-approved, thus considered clinically acceptable, and 87% required minor or no adjustments. Patient satisfaction was reported in 18 of 21 cases. ConclusionsThe RTT-only oART workflow for bladder cancer, complemented by a training program and on-call support from ROs and MPEs, demonstrated success. Patient experience is positive. It is currently introduced as standard in our clinic.

Impact of radiotherapy dose, fractionation and immunotherapeutic partner in a mouse model of HR+ mammary carcinogenesis.

Hormone receptor (HR)+ breast cancer is poorly responsive to immune checkpoint inhibitors (ICIs). In some settings, radiation therapy (RT) has been shown to mediate immunostimulatory effects and promote ICI sensitivity. We investigated whether hypofractionated RT may be successfully combined with ICIs in a mouse model of multifocal, metachronous HR+ mammary carcinogenesis. We hypothesized that focal RT targeting the first detectable (primary) tumor combined with ICIs may generate effective immunity, hence delaying the development of new lesions. Focal RT in various doses and fractionations limited primary tumor growth, with an optimum for a 20 Gy X 2 regimen (ablative in ∼90% of mice). The degree of primary disease control, however, did not necessarily correlate with overall survival (OS) extension, owing to changes in the development of new neoplastic lesions contributing to global tumor burden. Adding a PD-1 blocker to focal RT delivered in a 10 Gy X 3, 20 Gy X 2 or 8 Gy X 6 regimen failed to alter OS extension enabled by RT alone. Similar results were obtained with a CTLA4 blocker, an IL1B inhibitor, and a PD-1 blocker plus recombinant FLT3LG when combined with the 10 Gy X 3 regimen. In this model of HR+ mammary carcinogenesis, RT to the primary tumor ameliorates OS (to an extent depending on dose and fractionation). Increasing local control by RT alone or RT plus immunotherapy beyond a hitherto undefined threshold, however, does not necessarily inhibit the development of subsequent non-irradiated neoplasms and hence does not necessarily provide extra OS benefits.

Evaluating the efficacy of radiotherapy in patients with embryonal tumor with multilayered rosettes: A systematic review and meta-analysis

Abstract Background Embryonal tumor with multilayered rosettes (ETMR) is a rare and deadly pediatric central nervous system tumor often seen before the age of 3. ETMR consists of embryonal tumors with abundant neuropil and true rosettes, ependymoblastoma, and medulloepithelioma. The 5-year survival rate has been reported to be between 0% and 30%. Treatment of ETMR is very unstandardized and typically consists of surgical resection, chemotherapy, and radiotherapy. A systematic review was performed to better understand treatment-related outcome trends. Methods The authors performed a PRISMA guidelines-based systematic review of the literature. Survival curve analysis using Kaplan–Meier curves and Cox proportional hazards models were used to estimate survival rates between 2 groups and multiple risk factors, respectively. Results The average survival time was 31.1 months in patients treated with radiotherapy compared to 11.2 months in patients who did not. Radiotherapy was a significant covariate on overall survival (P < .001) with an 82% lower risk of death compared to patients who did not receive radiotherapy. The average survival time for patients with focal radiotherapy was 35.8 months compared to 29.8 months in patients with CSI radiotherapy, but there was a great number of patients with pretreatment metastasis in the CSI group. In patients without pretreatment metastasis, focal radiotherapy had non-inferior outcomes for survival rates and times. Conclusions Patients treated with radiotherapy in addition to chemotherapy demonstrated a significantly higher survival time. For patients with no metastasis prior to treatment, focal radiotherapy should be strongly considered.

Atypical Teratoid Rhabdoid Tumor of the Brain in a Young Adult With Down Syndrome: Case Report and Literature Review.

Atypical teratoid/rhabdoid tumor (ATRT) is an aggressive, malignant embryonal tumor with dismal long-term survival despite aggressive multimodal therapy. While this tumor typically presents in infancy or early childhood, there are published case reports of adult-onset ATRT. Making prognostic conclusions or therapeutic decisions for this older patient population remains challenging due to the paucity of these reports. A 25-year-old female with Down syndrome presented with dysphagia and facial droop and was found to have an avidly enhancing, cerebellopontine angle mass. Histology demonstrated sheets of rhabdoid cells with loss of INI1 expression, pathognomonic for ATRT. Further sequencing detected a frameshift SMARCB1 mutation and methylation profiling matched with high confidence to the MYC subclass of ATRT. The patient was treated with subtotal surgical resection and focal proton beam irradiation, followed by chemotherapy on a modified regimen due to concern for heightened risk of treatment-related toxicity. On most recent follow-up 22 months from diagnosis, the patient remains without evidence of disease. This report represents the first known case of ATRT in a young adult patient with Down syndrome, offering unique mechanistic insight into the tumorigenesis of ATRT. Further studies are needed to define an appropriate risk-adapted and standardized therapeutic approach for this patient population.

EPID-36. CLINICAL FEATURES OF 614 PRIMARY INTRACRANIAL GERM CELL TUMORS: AN 15-YEAR EXPERIENCE OF A SINGLE CENTER IN CHINA

Abstract Incidence of primary intracranial germ cell tumors (ICGCT) in Asian countries is higher than Western countries. This study aims to describe the characteristics of ICGCT patients in China. Data on all patients with ICGCT who were seen at the Department of Neuro-oncology, Sanbo Brain Hospital, Capital Medical University from 2007 to 2022 were collected retrospectively. Patient demographics, disease characteristics and treatment outcomes were analyzed. A total of 614 patients were identified, with 309 germinomas and 305 non-germinomatous germ cell tumors (NGGCT). The median age at diagnosis was 12.8 years. The male-female ratio is 2.4 to 1. The primary disease sites were mainly pineal gland and suprasellar region. Adults (age≥23) were more likely to develop germinomas (65.3%). 78% patients received radiotherapy after initial diagnosis. In M0 patients, whole brain radiotherapy was the most common approach, while in M+ was craniospinal radiotherapy. Whole ventricle radiotherapy was uncommon (4%). The most common chemotherapy regimen for germinoma was a combination of bleomycin, cisplatin and etoposide/tenipside; while for the NGGCT was ifosfamide combined with carboplatin/cisplatin and etoposide. For germinoma, the median recurrence-free survival (RFS) and overall survival (OS) were 150.3 months and 222 months; the 10 year RFS and OS were 58.2% and 85.1%, respectively. For NGGCT, the median RFS and OS were 80.4 months and 166.7 months; the 10 year RFS and OS were 46.9% and 60.5%. At relapse, four (0.65%) developed secondary malignancies. Seven (1.14%) developed extracranial dissemination. Chemotherapy and radiotherapy could improve the RFS and OS. Higher radiation dose was associated with better prognosis. The prognosis of focal radiotherapy alone was poor. M0 germinoma treated with focal radiotherapy alone were more likely relapse. This study suggested that treatment outcomes of our ICGCT patients are comparable with those in Western centers. Adjuvant chemotherapy and whole brain/craniospinal radiotherapy are pivotal treatment.

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.

PATH-43. MALIGNANT TRANSFORMATION OF MENINGEAL MELANOCYTOMA - GENETIC ALTERATIONS AND RESPONSE TO CHECKPOINT BLOCKADE IMMUNOTHERAPY

Abstract INTRODUCTION Meningeal melanocytomas are uncommon tumors that develop from leptomeningeal melanocytes. These tumors can exhibit aggressive behavior, leading to symptoms due to compression and potential invasion of nearby central nervous tissue. Case: In this report, we discuss the case of a 45-year-old man who was diagnosed 18 years ago with a meningeal melanocytoma in the right temporal region. He underwent complete resection with each recurrence and received focal intensity-modulated radiation therapy after a third recurrence in 2013. In May 2022, he developed progressive headaches and diplopia secondary to tumor recurrence on the right temporal region. Resection revealed that the tumor had progressed to malignant meningeal melanoma with 34 mitoses per 10 high-power fields. Next-generation sequencing (NGS) showed GNAQ mutation confirming tumor of central nervous system (CNS) origin, and also showed an SF3B1 mutation, indicating aggressive behavior. Several chromosomal abnormalities were also detected. Systemic workup revealed liver, lung, and bone metastasis. Liver biopsy confirmed meningeal melanoma of central origin. The patient received radiosurgery with a total of 30Gy over five fractions to intracranial surgical cavity, followed by three cycles of nivolumab and relatlimab. Unfortunately, the patient experienced severe intracranial and systemic progression, leading to his death six months after the malignant transformation. DISCUSSION Meningeal melanocytomas are rare however these tumors have a high recurrence rate with potential malignant transformation over time. NGS is a valuable tool for confirming the CNS origin of the tumor and predicting its aggressive behavior. Despite microscopic similarity with cutaneous melanomas, meningeal melanocytomas have different pathogenesis and do not seem to respond to immunotherapy, as observed in this case.

INNV-22. CEREBELLOPONTINE EPIDERMOID CYST TO SQUAMOUS CELL CARCINOMA: MALIGNANT TRANSFORMATION, LEPTOMENINGEAL CARCINOMATOSIS, AND MANAGEMENT

Abstract BACKGROUND Intracranial epidermoid cysts (EDC) are rare, slow-growing, congenital tumors, that generally follow a benign course. EDCs have a rare potential for transformation to squamous cell carcinoma (SCC). We present a case of a malignant EDC transformation to SCC with leptomeningeal (LM) dissemination. METHODS Case report and review of literature. CASE PRESENTATION A 44-year-old female presented for evaluation of left-sided tinnitus and sensorineural hearing loss, which revealed a left cerebellopontine angle (CPA) tumor. She underwent a subtotal resection at age 47. One year later, she had rapid symptomatic recurrence of the cyst, as well as LM deposits of the right internal acoustic canal bundle, the left trigeminal nerve, and along the lumbar and sacral spine. She underwent repeat resection of the CPA lesion, with pathology now consistent with SCC, with CDKN2A loss. She received focal radiation therapy at the posterior fossa and the lumbar spine. SCC-directed chemotherapy with pembrolizumab and carboplatin followed by 5 cycles of pembrolizumab monotherapy was given as adjuvant therapy, prior to her developing symptomatic LM disease. CONCLUSION Malignant transformation of intracranial EDC is a rare occurrence in these typically benign tumours. Prognosis is especially poor when there is associated LM involvement, with median survival noted to be 10 months. Awareness of this phenomenon amongst clinicians is needed to ensure appropriate surveillance and aggressive treatment if it remains within patient wishes, though there is no consensus on recommendations for treatment. The patient presented has maintained disease stability with LM dissemination for over 10 months and ongoing, with a regimen of chemoradiotherapy informed by therapeutic approach to systemic SCC. To our knowledge, this is the first reported case of EDC to SCC transformation and LM dissemination stabilized with chemoradiotherapy using an immune-checkpoint inhibitor.

PATH-41. PRIMARY BRAIN SARCOMA WITH DROP METASTASES AND LEPTOMENINGEAL DISEASE

Abstract INTRODUCTION Primary brain sarcoma is extremely rare and has a very poor prognosis. Sarcomas are a highly diverse group, with over 100 different subtypes identified in the recent WHO classification. Case: In this case, we describe a 51-year-old man diagnosed with primary right frontal poorly differentiated sarcoma. He experienced cognitive changes for weeks. Brain MRI revealed a lobulated mass with peripheral enhancement measuring 67 mm by 61 mm by 52 mm. He underwent gross total resection, and pathology indicated high-grade poorly differentiated sarcomatous lesions. Further analysis at Memorial Sloan Kettering and NIH failed to match any DNA methylation class. Next generation sequence (NGS) testing revealed mutation of NF2, CDKN2A, COL3A1, CD33, and PIK3CA genes, increased PD-L1 mRNA, and PD-L1 expression, greater than 50%. The conclusive diagnosis was a PD-L1 high poorly differentiated sarcoma, not otherwise specified. Since no primary site was found elsewhere, planned to treat it as a primary brain sarcoma. Patient underwent focal radiation therapy with a plan to start immunotherapy combination of anti-CTLA4 and anti-PD1 therapy. In addition, an anti-VEGF therapy with pazopanib because of the efficacy of pazopanib in the setting of soft tissue sarcomas. The patient completed IMRT on 07/13/2023 and presented with a new onset of left leg weakness and urinary incontinence on 07/25/2024, further neuraxis imaging with MRI showed local and distant intracranial recurrence with drop metastasis at C1, C5-C6, and S2. The patient was started on IMRT to address drop metastasis, however further clinical decline led to treatment discontinuation. DISCUSSION There is no consensus on treatment guidelines on primary brain sarcomas given that they are exceedingly rare. DNA methylation and NGS provided very valuable information. We were unable to find any reported cases of primary brain sarcoma with drop metastases and leptomeningeal disease in the literature.

CTNI-30. A PHASE 2 DOUBLE-BLIND, RANDOMIZED, PROSPECTIVE, PLACEBO CONTROLLED STUDY OF NANO₂TM COMBINED WITH RADIATION AND TEMOZOLOMIDE IN PATIENTS WITH NEWLY-DIAGNOSED GLIOBLASTOMA: RESTORE

Abstract INTRODUCTION Glioblastoma (GBM) commonly has extensive hypoxic regions, possibly due to thrombosis from tumor-produced pro-coagulant factors. Radiation-induced cell death relies on oxygen free radicals and oxygen fixation of DNA-strand breaks. In the absence of oxygen tumor cells can repair the DNA strand breaks leading to treatment resistance. Hypoxic cells also exhibit chemoresistance due to decreased drug efficacy, limited drug diffusion, and poor delivery to distant cells. This study hypothesizes that increasing oxygen delivery to hypoxic GBM tissue using NanO₂ (2% w/v dodecafluoropentane emulsion) infusion will enhance the effectiveness of radiation therapy (RT) and chemotherapy (CT). METHODS Patients diagnosed with GBM per CNS5-WHO criteria receive standard chemoradiation: 30 fractions of focal RT with 60 Gy, delivered as 2 Gy fractions five days per week for six weeks with concurrent oral TMZ at 75 mg/m²/day for six weeks. Patients are randomized in a 1:2 ratio to receive either a placebo (0.9% Sodium Chloride) or NanO₂ infusion administered immediately prior to each RT dose. Patients continuously breathe oxygen during infusion and RT. Following six weeks of RT with temozolomide, patients have a four-week break before starting adjuvant temozolomide. RESULTS Ten patients have been enrolled in the RESTORE trial. Seven continue to be followed through maintenance treatment and long term follow up. There have been 23 non-hematologic adverse events described as CTCAE severity grade 3 and above. Grade 4, hematologic toxicity occurred in two patients, with one patient experiencing prolonged pancytopenia necessitating hematologic support and discontinuation of temozolomide. Two patients discontinued therapy due to early tumor progression. CONCLUSION This study is ongoing, assessing the safety and potential efficacy of NanO₂ in improving treatment outcomes for GBM by enhancing oxygen delivery to hypoxic tumor regions.

PATH-42. METASTATIC ADENOID CYSTIC CARCINOMA OF BREAST WITH BRAIN METASTASES AND LEPTOMENINGEAL DISEASE

Abstract INTRODUCTION Adenoid cystic carcinoma (ACC) of the breast rarely metastasizes to the brain and leptomeninges. ACC is a rare type of breast cancer, accounting for less than 0.1% of cases. It is usually triple negative, but has a good prognosis when it is confined to the breast. Lymph node involvement is uncommon, occurring in less than 2% of cases, and distant metastases to the brain are extremely rare. Leptomeningeal disease has not been reported yet. Case: In this case, we describe a 57-year-old woman diagnosed with triple-negative ACC of the right breast, which had spread to the axillary lymph nodes and distant metastases to the lung. The diagnosis was confirmed by biopsies of both metastatic sites. The patient received vinorelbine and cisplatin treatment for 11 cycles followed by right needle localized lumpectomy. While awaiting for the next steps in treatment she was admitted to the hospital for altered mental status, saddle anesthesia, and urinary incontinence. Neuraxis MRI revealed numerous hemorrhagic and non-hemorrhagic brain metastasis with diffuse leptomeningeal disease. Cerebrospinal fluid analysis confirmed leptomeningeal disease with positive cytology for atypical epithelioid malignant cells. The patient underwent whole brain radiation and focal radiation treatment to specific areas of leptomeningeal disease. Although she initially improved after the first month of radiation, her condition deteriorated rapidly, preventing the initiation of the next line of treatment with high-dose methotrexate or capecitabine. DISCUSSION Adenoid cystic carcinoma of the breast is exceedingly rare however with a very good overall prognosis. It is uncommon for ACC to spread to regional lymph nodes, and even rarer for distant metastasis. Brain metastasis is also infrequently reported. There are no documented cases of metastatic ACC with leptomeningeal disease, so there is no consensus on the best course of treatment.

EXTH-56. INVESTIGATING THE EFFECTS OF INDIRUBINS IN PEDIATRIC DIFFUSE HIGH GRADE GLIOMA MODELS

Abstract Diffuse midline glioma (DMG) is a highly invasive and fatal pediatric brain tumor that arises from glial cells within the pons of the brainstem. Despite focal radiation treatment, DMG continues to have a poor prognosis, with a median survival of less than 10 months. A significant challenge in treating DMG is the blood-brain barrier (BBB), which tightly restricts access to therapeutic agents, preventing drugs from reaching the brain at effective concentrations. Previous studies from the Lawler lab have shown that the indirubin derivative 6-bromoindirubin-3′-acetoxime (BIO-acetoxime/BIA) has anti-invasive properties and can enhance survival in glioblastoma xenograft models. We investigated the effects of BIA on pediatric glioma models using various assays. In an in vitro scratch migration assay, BIA significantly slowed cell migration at a concentration of 1µM in pediatric glioma cells over 72 hours. Additionally, BIA was shown to modulate tumor vasculature and improve drug delivery to tumors by targeting tight junctions in tumor-associated endothelium. BIA treatment increased dextran uptake into 3D BBB models and lowered endothelial cell permeability in vitro by reducing the expression of tight junction proteins, as shown by staining and a decrease in TEER values. Furthermore, BIA’s anti-angiogenic effects were demonstrated through staining, showing significant alterations in angiogenesis-related protein expression. To assess potential synergistic interactions, a drug screen was performed on a panel of pediatric glioma cell lines identifying several FDA-approved drugs that combine well with BIA. Drugs identified in the screen are currently under investigation. Our hypothesis is that BIA could be an effective therapeutic agent for DMG by targeting tumor invasion, angiogenesis, and improving drug potency and delivery through modulation of endothelial cell tight junctions. Future studies will focus on elucidating the underlying mechanisms and developing drug formulations for in vivo studies to assess the translational potential of this approach.

Role of epidural disease in local control of spinal metastases treated with stereotactic body radiation therapy.

Spinal metastases can be contained in the bone or have epidural spread. Whether the extent of epidural involvement changes tumor response to therapy is unknown. The decision of when to treat disease progression with focal radiation therapy with or without surgery vs. systemic therapy is debated. The present study compared outcomes and local tumor control after stereotactic body radiation therapy (SBRT) between patients with spine metastases localized to the bone (Bilsky 0) vs. patients with mild epidural spread (Bilsky 1). A retrospective analysis of a prospectively maintained database of adult oncological patients who underwent SBRT to the spine at a single, large, tertiary care facility from August 2010 to January 2021 was performed. Patients with Bilsky grades 1a, 1b and 1c were grouped and compared. Approximately half (53.7%) of the 255 patients identified had Bilsky grade 1 epidural disease. Of the 311 spine treatment sites, 86 (27.7%) had a radiosensitive histology, 116 (37.3%) had intermediate radiosensitivity and 109 (35.0%) had a radioresistant histology. Patients with Bilsky grade 1 were more predisposed to receive surgery followed by SBRT compared with those with Bilsky grade 0 (21.0% vs. 6.3%; P=0.0002). Patients with Bilsky grade 0 compression had 92.0% local control at 12 months and 85.8% local control at 24 months; patients with Bilsky grade 1 compression had 85.6% local control at 12 months and 77.6% local control at 24 months. Biologically effective dose and infield progression between patients presenting with Bilsky grade 0 and 1 compression were not statistically different. Local control rates did not differ significantly between Bilsky grade 0 and grade 1 patients following treatment with spinal SBRT. However, patients with grade 1 disease were more likely to receive surgery before SBRT. Overall, evidence indicates that patients may benefit from treatment with SBRT before epidural disease progresses to requiring separation surgery.

Pediatric metastatic extracranial high-grade glioma: A case report and literature review

Abstract We report a case of a 10-year-old male with a right frontal diffuse pediatric-type high-grade glioma (HGG), H3-wild-type (WT), and IDH-WT, diagnosed at the age of 9 years, who underwent gross total resection, 60 Gy focal proton radiation in 30 fractions to the resection cavity with concurrent temozolomide followed by maintenance chemotherapy with temozolomide and lomustine. One month after completion of maintenance chemotherapy, he developed subcutaneous swelling in the right temporal region and was treated with antibiotics for presumed lymphadenitis. Two months later, he developed a recurrent painless right parietal soft tissue mass that failed to respond to antibiotic therapy. This prompted evaluation by MRI which revealed new enhancing masses in the cerebellum and extracranial soft tissue mass in the right temporal region. He underwent gross total resection of both masses. Pathologic analysis confirmed both masses as recurrent HGG. Molecular markers, however, differed between the 2 sites of recurrence. He proceeded to complete hypofractionated proton therapy at sites of recurrence. Three months later, he was found to have tumor dissemination into the spine and brain for which he received proton therapy to the whole spine and brain. Due to the presence of CDK4 amplification at diagnosis and both sites of tumor recurrence, he then received palliative treatment with the CDK4/6 inhibitor, abemaciclib, for the final 5 months of his life. Since extracranial HGG is a rare presentation, with few cases reported in the pediatric population, we report this case and review previously published literature.

Photoperiodism, testosterone and adult neurogenesis in canaries (Serinus canaria).

Domestic strains of canaries (Serinus canaria) variably respond to photoperiod changes and apparently stay in breeding state for extended periods. Fife Fancy canaries are supposed to be similar to the native species living at 27-39° north where photoperiod significantly changes across the year. Our birds showed reproductive cycles when exposed to light regimes mimicking the annual cycle of photoperiod. However after 6 months in short days (SD: 8L:16D), males developed large testes, as observed by X-ray tomography, and intense singing. Switching to long days (LD: 16L:8D) did not further increase song rate nor testes size but increased song duration, number of syllables per song, and trill occurrence frequency. No sign of regression was observed after 12 weeks in LD but return to SD produced a rapid decrease in testes size and singing activity below values in birds maintained throughout in SD. Fife Fancy thus does not seem to develop absolute but only relative refractoriness. The relatively high singing activity expressed by SD-photosensitive males does not seem to depend on high testosterone (T) concentrations. Singing did not correlate with plasma testosterone (T). Treatment with ATD + Flutamide only marginally decreased song rate and did not affect song quality nor song control nuclei volume. These birds are either supersensitive to low T levels or their reproductive physiology is activated by other mechanisms. Neurogenesis is increased by T and by LD but the function of new neurons incorporated in HVC is poorly understood. We developed a procedure based on X-ray focal irradiation to deplete neural progenitors adjacent to HVC and study the functional consequences. The decrease in neurogenesis increased the variability of T-induced songs in females and decreased their bandwidth. Neurogenesis in HVC thus plays a role in song production and X-ray focal irradiation represents an excellent tool to analyze adult neurogenesis.

Ultralow-dose irradiation enables engraftment and intravital tracking of disease initiating niches in clonal hematopoiesis

Recent advances in imaging suggested that spatial organization of hematopoietic cells in their bone marrow microenvironment (niche) regulates cell expansion, governing progression, and leukemic transformation of hematological clonal disorders. However, our ability to interrogate the niche in pre-malignant conditions has been limited, as standard murine models of these diseases rely largely on transplantation of the mutant clones into conditioned mice where the marrow microenvironment is compromised. Here, we leveraged live-animal microscopy and ultralow dose whole body or focal irradiation to capture single cells and early expansion of benign/pre-malignant clones in the functionally preserved microenvironment. 0.5 Gy whole body irradiation (WBI) allowed steady engraftment of cells beyond 30 weeks compared to non-conditioned controls. In-vivo tracking and functional analyses of the microenvironment showed no change in vessel integrity, cell viability, and HSC-supportive functions of the stromal cells, suggesting minimal inflammation after the radiation insult. The approach enabled in vivo imaging of Tet2+/− and its healthy counterpart, showing preferential localization within a shared microenvironment while forming discrete micro-niches. Notably, stationary association with the niche only occurred in a subset of cells and would not be identified without live imaging. This strategy may be broadly applied to study clonal disorders in a spatial context.