K27M Mutation Research Articles

Multiparametric MRI-Based Radiomics Model for Predicting H3 K27M Mutant Status in Diffuse Midline Glioma: A Comparative Study Across Different Sequences and Machine Learning Techniques.

ObjectivesThe performance of multiparametric MRI-based radiomics models for predicting H3 K27M mutant status in diffuse midline glioma (DMG) has not been thoroughly evaluated. The optimal combination of multiparametric MRI and machine learning techniques remains undetermined. We compared the performance of various radiomics models across different MRI sequences and different machine learning techniques.MethodsA total of 102 patients with pathologically confirmed DMG were retrospectively enrolled (27 with H3 K27M-mutant and 75 with H3 K27M wild-type). Radiomics features were extracted from eight sequences, and 18 feature sets were conducted by independent combination. There were three feature matrix normalization algorithms, two dimensionality-reduction methods, four feature selectors, and seven classifiers, consisting of 168 machine learning pipelines. Radiomics models were established across different feature sets and machine learning pipelines. The performance of models was evaluated using receiver operating characteristic curves with area under the curve (AUC) and compared with DeLong’s test.ResultsThe multiparametric MRI-based radiomics models could accurately predict the H3 K27M mutant status in DMG (highest AUC: 0.807–0.969, for different sequences or sequence combinations). However, the results varied significantly between different machine learning techniques. When suitable machine learning techniques were used, the conventional MRI-based radiomics models shared similar performance to advanced MRI-based models (highest AUC: 0.875–0.915 vs. 0.807–0.926; DeLong’s test, p > 0.05). Most models had a better performance when generated with a combination of MRI sequences. The optimal model in the present study used a combination of all sequences (AUC = 0.969).ConclusionsThe multiparametric MRI-based radiomics models could be useful for predicting H3 K27M mutant status in DMG, but the performance varied across different sequences and machine learning techniques.

A case of ganglioglioma grade 3 withH3 K27Mmutation arising in the medial temporal lobe in an elderly patient

The mutation p.K27M inH3F3A(H3K27M mutation) is mainly detected in diffuse midline glioma. However, recent studies have demonstrated thatH3K27M mutation could also be observed in a subset of gangliogliomas. Importantly, mostH3K27‐mutated ganglioglioma cases also harborBRAFV600E mutation. Herein, we report a rare case ofH3K27M‐mutated ganglioglioma grade 3 withoutBRAFmutation arising in the medial temporal lobe in an elderly man. A small biopsy specimen was sampled. The pathological diagnosis was diffuse astrocytoma. The tumor progressed gradually during an 18‐month follow‐up period. Gadolinium enhancement on magnetic resonance imaging was noted 36 months after the biopsy. The patient was referred to a hospital for tumor resection. Histological analysis of resected specimens led to a diagnosis of ganglioglioma grade 3 with H3 K27M mutation. The patient underwent concurrent temozolomide chemotherapy with radiotherapy. Although the patient's condition deteriorated after chemotherapy due to disease progression, he survived for more than 23 months after tumor resection. We present this rare case and discuss the involvement ofH3K27M mutation in ganglioglioma grade 3.

Clinicoradiological characteristics of primary spinal cord H3 K27M-mutant diffuse midline glioma.

Primary spinal cord H3 K27M-mutant diffuse midline glioma (DMG) is a rare and devastating pathological entity. However, little attention has been paid to this disease. As a result, its clinicoradiological characteristics have yet to be described. The aim of this study was to describe the clinicoradiological characteristics of primary intramedullary H3 K27M-mutant DMG and to compare this tumor with the H3 K27 wild-type to explore potential features that could differentiate the two. A total of 59 patients with pathologically confirmed intramedullary astrocytoma were included in this study. The cohort was divided into an H3 K27M-mutant group and H3 K27 wild-type group based on the status of H3 K27M according to an immunohistochemistry method. Demographic data, MRI features, and molecular information were collected. Multivariate logistic regression was conducted to investigate variables that might have a role in differentiating an H3 K27M DMG from an H3 K27 wild-type tumor. Only symptom duration showed an independent association with the H3 K27M mutation (OR 0.82, 95% CI 0.68-0.94, p = 0.016). Patients with spinal cord H3 K27M-mutant DMG had a shorter symptom duration than patients with H3 K27 wild-type glioma. No significant difference was found in terms of MRI features between the H3 K27M-mutant and H3 K27 wild-type groups. Additionally, H3 K27M-mutant DMG frequently demonstrated overexpression of p53. Survival outcome did not show a statistical difference between the H3 K27-mutant subgroup and H3 K27 wild-type subgroup in histologically high-grade astrocytoma. Symptom duration was associated with an H3 K27M mutation in intramedullary astrocytoma. MRI features were heterogeneous, and no imaging feature was able to predict the H3 K27M mutation. The H3 K27M mutation did not impact survival outcome in spinal histologically high-grade astrocytoma.

Diffusion and perfusion imaging biomarkers of H3 K27M mutation status in diffuse midline gliomas.

H3K27M-mutant diffuse midline gliomas (M-DMGs) exhibit a clinically aggressive course. We studied diffusion-weighted imaging (DWI) and perfusion (PWI) MRI features of DMG with the hypothesis that DWI-PWI metrics can serve as biomarkers for the prediction of the H3K27M mutation status in DMGs. A retrospective review of the institutional database (imaging and histopathology) of patients with DMG (July 2016 to July 2020) was performed. Tumoral apparent diffusion coefficient (ADC) and peritumoral ADC (PT ADC) values and their normalized values (nADC and nPT ADC) were computed. Perfusion data were analyzed with manual arterial input function (AIF) and leakage correction (LC) Boxerman-Weiskoff models. Normalized maximum relative CBV (rCBV) was evaluated. Intergroup analysis of the imaging variables was done between M-DMGs and wild-type (WT-DMGs) groups. Ninety-four cases (M-DMGs-n = 48 (51%) and WT-DMGs-n = 46(49%)) were included. Significantly lower PT ADC (mutant-1.1 ± 0.33, WT-1.23 ± 0.34; P = 0.033) and nPT ADC (mutant-1.64 ± 0.48, WT-1.83 ± 0.54; P = 0.040) were noted in the M-DMGs. The rCBV (mutant-25.17 ± 27.76, WT-13.73 ± 14.83; P = 0.018) and nrCBV (mutant-3.44 ± 2.16, WT-2.39 ± 1.25; P = 0.049) were significantly higher in the M-DMGs group. Among thalamic DMGs, the min ADC, PT ADC, and nADC and nPT ADC were lower in M-DMGs while nrCBV (corrected and uncorrected) was significantly higher. Receiver operator characteristic curve analysis demonstrated that PT ADC (cut-off-1.245), nPT ADC (cut-off-1.853), and nrCBV (cut-off-1.83) were significant independent predictors of H3K27M mutational status in DMGs. DWI and PWI features hold value in preoperative prediction of H3K27M-mutation status in DMGs.

Diffuse midline glioma

Diffuse midline glioma(DMG), H3 K27M-mutant is an infiltrative midline high-grade glioma with predominantly astrocytic differentiation and a K27M mutation in either H3F3A or HIST1H3B/C. It is commonly located in the brain stem, thalamus, and spinal cord. DMG is predominant in children but can occur in adults. Brain stem disease, known as diffuse intrinsic pontine glioma(DIPG), is the representative: -80% harbor the H3 K27M mutation. Generally, the prognosis of DMG is poor: the 2-year survival rate is < 10%, despite intensive research and therapies. Consequently, radiation is the only treatment and there is no effective chemotherapeutic regimen. The recent findings concerning the genetic profiles of DMG shed light on precision medicine. Until today, approximately 250 clinical trials with molecular targeted therapy as a strategy have been conducted for different biological pathways in DMG. Unfortunately, none of them has shown significant efficacy for DMG. One of the problems in these clinical trials is insufficient knowledge of whether the used molecular targeted agents penetrate the blood-brain barrier. Continuous efforts to develop effective precision medicine against DMG should pave the way for overcoming DMG in the future.

Clinical Features and Prognosis of Diffuse Midline Glioma: A Series of 24 Cases.

Diffuse midline glioma (DMG) which occurs in midline structures and characterized by harboring K27M mutation in genes encoding the histone 3 protein is classified as World Health Organization (WHO) grade IV regardless of histological findings and has a poor prognosis. Nevertheless, because of its relatively rare incidence compared with other high-grade gliomas, a comprehensive description encompassing clinical features and genomic profiles of DMG is still lacking. In this study, we analyzed data of 24 patients who were diagnosed as DMG which was confirmed by surgical specimens in both pediatric and adult patients. We described the clinical outcomes of patients with DMG and their genomic profiles through a retrospective analysis of 24 patients with DMG. The clinical characteristics of the 24 patients with DMG were analyzed. Ten patients (41%) underwent tumor resection and 14 patients (59%) underwent tumor biopsy. The median overall survival was 10.4 months (95% confidence interval [CI], 8.4 to 12.5) and progression free survival was 3.9 months (95% CI, 2.6 to 5.2). Fifteen patients (62%) were accompanied by hydrocephalus. None of the patient, tumor, or treatment factors had any significant associated with survival. In both immunohistochemistry staining (n=24) and targeted next generation sequencing (n=15), TP53 mutation was the most common genetic mutation (25% and 46%, respectively) found in the patients except alterations in histone 3 protein. Although surgical treatment of patient with DMG does not affect the overall survival prognosis, it can help improve the patient's accompanying neurological symptoms in some limited cases. Hydrocephalus is often accompanied with DMG and treatment for hydrocephalus is often also required. Multidisciplinary therapeutic approach is needed.

Multimodal MR imaging signatures to identify brain diffuse midline gliomas with H3 K27M mutation.

BackgroundConventional MR imaging has limited value in identifying H3 K27M mutations. We aimed to investigate the capacity of quantitative MR imaging variables in identifying the H3 K27M mutation status of diffuse midline glioma.Materials and MethodsTwenty‐three patients with H3 K27M mutation and thirty‐two wild‐type patients were recruited in this retrospective study, all of whom underwent multimodal MR imaging. Clinical data and quantitative MR imaging variables were explored by subgroup analysis stratified by age (juveniles and adults). Then, a logistic model for all patients was constructed to identify potential variables for predicting K27M mutation status. Besides, a retrospective validation set including 13 patients was recruited. The C‐index and F1 score were used to evaluate the performance of the prediction model.ResultsIt turned out that patients with H3 K27M mutation were younger in the adult subgroup. In the mutation group, some relative apparent diffusion coefficient (rADC) histogram parameters and myo‐inositol/creatine plus phosphocreatine (Ins/tCr) ratio were lower than in the wild‐type group of both juveniles and adults (p < 0.05). After nested cross‐validation and LASSO algorithm, the age, Ins/tCr, and rADC_15th were selected as potential predictors for H3 K27M mutation in the model. The nomogram model showed good diagnostic power with a validated C‐index of 0.884. In addition, the area under the curve (AUC) was 0.898 (0.976 in validation set) and the F1 score was 0.732.ConclusionsIn conclusion, age, rADC_15th, and Ins/tCr values were helpful in identifying H3 K27M mutations in midline gliomas.

Magnetic Resonance Imaging Characteristics of Molecular Subgroups in Pediatric H3\xa0K27M Mutant Diffuse Midline Glioma

PurposeRecent research identified histone H3 K27M mutations to be associated with a dismal prognosis in pediatric diffuse midline glioma (pDMG); however, data on detailed MRI characteristics with respect to H3 K27 mutation status and molecular subgroups (H3.1 and H3.3 K27M mutations) are limited.MethodsStandardized magnetic resonance imaging (MRI) parameters and epidemiologic data of 68 pDMG patients (age <18 years) were retrospectively reviewed and compared in a) H3 K27M mutant versus H3 K27 wildtype (WT) tumors and b) H3.1 versus H3.3 K27M mutant tumors.ResultsIntracranial gliomas (n = 58) showed heterogeneous phenotypes with isointense to hyperintense signal in T2-weighted images and frequent contrast enhancement. Hemorrhage and necrosis may be present. Comparing H3 K27M mutant to WT tumors, there were significant differences in the following parameters: i) tumor localization (p = 0.001), ii) T2 signal intensity (p = 0.021), and iii) T1 signal homogeneity (p = 0.02). No significant imaging differences were found in any parameter between H3.1 and H3.3 K27M mutant tumors; however, H3.1 mutant tumors occurred at a younger age (p = 0.004). Considering spinal gliomas (n = 10) there were no significant imaging differences between the analyzed molecular groups.ConclusionWith this study, we are the first to provide detailed MR imaging data on H3 K27M mutant pDMG with respect to molecular subgroup status in a large patient cohort. Our findings may support diagnosis and future targeted therapeutic trials of pDMG within the framework of the radiogenomics concept.

BT-1 An autopsy case of multicentric malignant glioma, H3K27M mutant

Introduction: In 2016, the World Health Organization (WHO) defined diffuse midline glioma, H3K27M mutant (WHO Grade 4) as a tumor with K27M mutation in histone H3.3 (H3F3A) or H3.1 (HIST1H3B/C) that develops mainly in the midline regions of the central nervous system. Here, we report a rare case of the abovementioned disease with remote multiple lesions in addition to the midline regions that was diagnosed on the initial visit. Case: The 52-year-old man, suffered from dysarthria, dysphagia, gait disturbance, and headache that gradually worsened over several months. Non-contrast-enhanced lesions were noted in the pons(swelling and involvement of the basilar artery trunk), cerebellum, thalamus, fornix, periventricular area, hippocampus, medial aspect of bilateral frontal lobes, and distally in the right frontal cortex and apical region of the left temporal lobe. The open biopsy was performed for left cerebellar surface lesion, and the pathological and genetic diagnosis was diffuse midline glioma, H3K27M mutant. Extended focal radiation at 50Gy/25fr and corpus callosal/cerebellar boost at 10Gy/5fr were performed. The lesions were markedly reduced, and neurological symptoms were also alleviated. However, 20 months after the initial visit, neurological symptoms had worsened and cerebrospinal fluid dissemination occurred, after that died at 29 months. An autopsy revealed tumor invasion mainly in the midline regions of the cerebrum and in the cerebellum, brain stem, pituitary gland, entire spinal cord, and cauda equina. Immunostaining of the distally cerebral cortex lesions showed that with a negative result for H3G34V. Discussion/Conclusion: It was suggested that caution is required for primary differential diagnosis may be presented at multiple lesions such as remote cerebral cortex of diffuse midline glioma, H3K27M-mutant.

GEN-7 Liquid biopsy in brain tumor patients -The present and future-

We have previously published liquid biopsy for the diagnosis of brain tumors including PCNSL (JCO Precision Oncology, 2019; Leukemia and Lymphoma, 2019) and diffuse midline gliomas (DMG) (Diagnostics, 2021). We used the Maxwell RSC cfDNA extraction kit to extract circulating tumor DNA (ctDNA from) 1 milliliter of cerebrospinal fluid (CSF), and droplet digital PCR to detect MYD88 L265P mutations in PCNSL and H3F3A K27M mutations in DMG. From our initial experience, we were able to detect a high rate of MYD88 mutations in PCNSL, but not H3F3A mutations in DMG. We also observed that higher concentrations of ctDNA were obtained when prompt centrifugation and storage were done after obtaining CSF. Application of liquid biopsy to early detection of relapse and monitoring of treatment relapse are highly anticipated. In cases of PCNSL, we perform liquid biopsy when relapse is suspected on post-contrast MRI. However interestingly, the rate of MYD88 mutations detected is lower than that of newly-diagnosed cases. We would also like to share our experience performing liquid biopsy in conjunction with CSF cytology in brain tumor patients with evidence of leptomeningeal disease. From our initial experience, we would like to discuss the present limitations and future prospects of liquid biopsy in brain tumor patients.

Erratum. A multicenter analysis of the prognostic value of histone H3 K27M mutation in adult high-grade spinal glioma.

Erratum. A multicenter analysis of the prognostic value of histone H3 K27M mutation in adult high-grade spinal glioma.

“Pain in the Neck”: Acute-Onset Neck Pain in an Adolescent Girl

A 10-year-old girl presents to the pediatric emergency department (ED) with acute onset of sharp neck pain and torticollis that began on awakening the morning of presentation. She has had shoulder pain for the past 3 days and in addition developed pain in her neck the morning of presentation. This morning she developed numbness in her legs and inability to walk. She has no associated headache, dizziness, fever, or urinary or bowel incontinence.She had a recent ED visit for flank pain due to constipation treated with polyethylene glycol 9 days earlier. Her medical history includes asthma and eczema. She is fully immunized. She has had a 12-lb (5.4-kg) weight loss in the previous 7 weeks.Her initial vital signs are as follows: temperature, 98.8°F (37.1°C); pulse, 104 beats/min; blood pressure, 138/91 mm Hg; respiratory rate, 20 breaths/min; and oxygen saturation, 100% on room air. She is generally well-appearing but in acute distress secondary to neck pain. She is lying in bed holding her neck laterally flexed to the right, refusing to move it, and she cries out in pain with any attempt to move her head to midline. She has abdominal tenderness with normal bowel sounds and no hepatosplenomegaly or masses. Her neurologic examination is significant for 3/5 strength in the upper extremities and inability to move the lower extremities spontaneously except toe wiggling. Sensation is intact throughout. She has a flexor plantar response bilaterally, but no deep tendon reflexes could be elicited in her upper or lower extremities. She is refusing to sit up or move in bed due to neck pain.A complete blood cell count, comprehensive metabolic panel, C-reactive protein level, and creatine phosphokinase level were all normal.Neck pain, a common chief complaint in the pediatric ED, is most often musculoskeletal, traumatic, or infectious in origin. The typical etiologies include muscular spasm; cervical spine injury; peritonsillar, retropharyngeal, or other deep neck abscess; and meningitis or epidural abscess. Less commonly, neck pain can be secondary to arthritis, congenital malformations, vertebral anomalies, and posterior fossa or cervical spinal tumors. (1) It is important to take a thorough history with attention to the timing and specific characteristics of pain, including quality, radiation, aggravating or relieving factors, and any associated symptoms to help build a differential diagnosis and determine the need for radiologic and laboratory investigation. (2)Neurology was consulted and recommended gabapentin and ketorolac treatment for pain. She was admitted for further evaluation and management. The following day she was noted to have normal strength and reflexes in the upper extremities but 2/5 strength, hypotonia, and absent reflexes in the lower extremities, including absent Babinski sign. She also developed urinary retention requiring Foley catheter placement. Magnetic resonance imaging (MRI) of the brain and complete spine was performed and demonstrated a solidly enhancing lesion in the thoracic cord at T5-T6 through T6-T7 with a peripherally enhancing single cystic component extending cranially to approximately C5 (Fig 1). There were areas of hypointensity in the upper thoracic portion consistent with hemorrhage, as well as T2 hyperintensity extending cranially to the craniocervical junction (Fig 2) and caudally to the conus (Fig 3), consistent with edema. Neurosurgery was consulted and recommended dexamethasone treatment to reduce edema. The patient was brought to the operating room for laminoplasty and tumor resection, after which she experienced lower extremity paralysis and urinary incontinence. Surgical pathology demonstrated a diffuse midline glioma, H3 K27M mutation (World Health Organization grade IV). Oncology discussed treatment options with the family and noted that

A multicenter analysis of the prognostic value of histone H3 K27M mutation in adult high-grade spinal glioma.

High-grade spinal glioma (HGSG) is a rare but aggressive tumor that occurs in both adults and children. Histone H3 K27M mutation correlates with poor prognosis in children with diffuse midline glioma. However, the role of H3 K27M mutation in the prognosis of adults with HGSG remains unclear owing to the rarity of this mutation, conflicting reports, and the absence of multicenter studies on this topic. The authors studied a cohort of 30 adult patients with diffuse HGSG who underwent histological confirmation of diagnosis, surgical intervention, and treatment between January 2000 and July 2020 at six tertiary academic centers. The primary outcome was the effect of H3 K27M mutation status on progression-free survival (PFS) and overall survival (OS). Thirty patients (18 males and 12 females) with a median (range) age of 50.5 (19-76) years were included in the analysis. Eighteen patients had H3 K27M mutation-positive tumors, and 12 had H3 K27M mutation-negative tumors. The median (interquartile range) PFS was 3 (10) months, and the median (interquartile range) OS was 9 (23) months. The factors associated with increased survival were treatment with concurrent chemotherapy/radiation (p = 0.006 for PFS, and p ≤ 0.001 for OS) and American Spinal Injury Association grade C or better at presentation (p = 0.043 for PFS, and p < 0.001 for OS). There were no significant differences in outcomes based on tumor location, extent of resection, sex, or H3 K27M mutation status. Analysis restricted to HGSG containing necrosis and/or microvascular proliferation (WHO grade IV histological features) revealed increased OS for patients with H3 K27M mutation-positive tumors (p = 0.017). Although H3 K27M mutant-positive HGSG was associated with poor outcomes in adult patients, the outcomes of patients with H3 K27M mutant-positive HGSG were somewhat more favorable compared with those of their H3 K27M mutant-negative HGSG counterparts. Further preclinical animal studies and larger clinical studies are needed to further understand the age-dependent effects of H3 K27M mutation.

Targeted therapy with anlotinib for a H3K27M mutation diffuse midline glioma patient with PDGFR-α mutation: a case report

H3K27M-mutant diffuse midline glioma (H3K27M-mt DMG) was a novel entity, which was defined by K27M mutations in H3F3A or HIST1H3B/C in the 2016 WHO updated fourth edition of the central nervous system (CNS) tumor classification. There is an urgent need for effective therapeutic strategies. Anlotinib is a multitarget tyrosine kinase inhibitor, which has not been reported for H3K27M-mt DMG treatment. Here, we firstly reported an adult multifocal H3K27M-mt DMG patient benefiting from anlotinib. This report provides a promising treatment option for H3K27M-mt DMG patients.

Is H3 K27M mutation testing relevant in the diagnostic routine of WHO grade 4 gliomas exclusively located in the corpus callosum in adults?

Is H3 K27M mutation testing relevant in the diagnostic routine of WHO grade 4 gliomas exclusively located in the corpus callosum in adults?

Thalamic gliomas in adults: a systematic review of clinical characteristics, treatment strategies, and survival outcomes.

Thalamic gliomas are rare neoplasms that pose significant surgical challenges. The literature is limited to single-institution retrospective case series. We systematically review the literature and describe the clinical characteristics, treatment strategies, and survival outcomes of adult thalamic gliomas. Relevant articles were identified on PubMed, Scopus, and Cochrane databases. Papers containing cases of adult thalamic gliomas with clinical outcome data were included. A comprehensive review of clinical characteristics and survival analysis was conducted. We included 25 studies comprising 617 patients. The median age was 45years (male = 58.6%). Glioblastoma was the most frequent histological type (47.2%), and 82 tumors were H3 K27M-mutant. Motor deficit was the most common presenting symptom (51.8%). Surgical resection was performed in 69.1% of cases while adjuvant chemotherapy and radiotherapy were administered in 56.3% and 72.6%, respectively. Other treatments included laser interstitial thermal therapy, which was performed in 15 patients (2.4%). The lesion laterality (P = 0.754) and the surgical approach (P = 0.111) did not correlate with overall survival. The median progression-free survival was 9months, and the overall two-year survival rate was 19.7%. The two-year survival rates of low-grade and high-grade thalamic gliomas were 31.0% and 16.5%, respectively. H3 K27M-mutant gliomas showed worse overall survival (P = 0.017). Adult thalamic gliomas are associated with poor survival. Complete surgical resection is associated with improved survival rates but is not always feasible. H3 K27M mutation is associated with worse survival and a more aggressive approach should be considered for mutant neoplasms.

PATH-04. LEPTOMENINGEAL DISEASE IN PATIENTS WITH HISTONE-MUTANT GLIOMAS

Abstract INTRODUCTION The 2016 WHO classification describes a subtype of midline gliomas harboring histone 3 (H3) K27M mutations, and the upcoming 2021 edition may include a new subtype of hemispheric diffuse gliomas with H3 G34R/V mutations. Since we began to perform molecular profiling at Memorial Sloan Kettering Cancer Center (MSKCC) we have observed an increased prevalence of leptomeningeal disease (LMD) in this population. However, the incidence and clinical behavior of LMD has not been well defined. METHODS This is a retrospective study of patients with H3-mutant gliomas at MSKCC diagnosed from 01/2012 to 02/2021, either by tumor biopsy or by cerebrospinal fluid (CSF). Histone mutations were identified through next-generation sequencing (NGS). RESULTS We found 40 patients (pts) harboring H3 mutations (K27M mutations in 31 pts, G34R/V in 8, and both in one), with 2/40 (5%) mutations identified through CSF NGS only and rest in tumor tissue. Median age was 20.5 years (4-70); 25 were male. Tumor location was midline for K27M-mutant tumors (thalamus [N=15], brainstem [N=10], spine [N=5], pineal gland [N=1]) and hemispheric for G34R/V-mutant tumors; tumor with both mutations was thalamic. LMD was diagnosed in 22/40 (55%) pts radiographically, including 19/31 (61%) of K27M-mutant pts and 3/8 (38%) of G34R/V-mutant pts (patient with both mutations did not develop LMD). At analysis, 10 patients remain alive. Median time from diagnosis to LMD was 8.8 months (0-44.4), with median OS of 6.5 months (0.3-34) after LMD diagnosis. CONCLUSION More than half of patients with histone-mutant gliomas develop LMD, including over a third of patients with G34R/V mutations. Neuroaxis imaging should be performed in conjunction with CSF studies in histone-mutant gliomas. Besides, CSF NGS represents an important tool to identify molecular profile of tumors when biopsy is not feasible or there is limited tissue for analysis.

IMMU-08. NOVEL NANOPARTICLE-BASED DELIVERY OF H3.3K27M PEPTIDE TO TUMOR-ASSOCIATED MACROPHAGES ENHANCES THE TUMOR HOMING OF H3.3K27M-TCR TRANSDUCED T-CELLS IN HLA-A2/DR1 TRANSGENIC MICE WITH H3.3K27M+

Abstract We have identified a novel HLA-A*02:01-restricted CD8 T-cell epitope encompassing the H3.3K27M mutation and a corresponding high-affinity T-cell receptor (TCR) that recognizes the epitope. While the development of adoptive cell transfer therapy using TCR-transduced T-cells holds a promise, we still need to overcome multiple challenges, such as suboptimal T-cell trafficking and the immunosuppressive environment of malignant glioma. For example, tumor-associated macrophages (TAMs) mediate immunosuppression but do not function as effective antigen-presenting cells. We have developed a novel cholesteryl pullulan (CHP) nanogel as a highly biocompatible and efficient vaccine delivery system targeting TAMs. In this study, we investigated whether the CHP nanogel loaded with the H3.3K27M peptide would deliver the peptide to TAMs and convert TAMs to better antigen-presenting cells that enhance the anti- H3.3K27M+ glioma activity of the TCR-transduced T-cells. As a clinically relevant mouse model, we used HLA-A2/HLA-DR1-transgenic mice and generated a syngeneic glioma cell line that expresses H3.3K27M from their astrocytes. We also generated a retroviral vector encoding the H3.3K27M-specific TCR for transduction of mouse T cells. HLA-A2/HLA-DR1-transgenic mice bearing day 16 intracerebral H3.3K27M+ glioma received an intravenous administration of the CHP nanogel along with poly-ICLC, a Toll-like receptor 3 agonist. The mice then received an intravenous infusion of TCR-transduced or control, non-transduced T-cells on the following day. The triple combination regimen with the CHP, poly-ICLC and TCR-transduced T-cells significantly suppressed the tumor growth, associated with increased levels of T-cell infiltration into the tumors compared with the dual-therapy with poly-ICLC and TCR-T-cells without the CHP. Furthermore, TAMs isolated from CHP-treated mice showed evidence of CHP-uptake, abilities to stimulate proliferation of TCR-transduced T-cells, and higher levels of HLA.A2 expression. These results suggest that the antigen-loaded CHP nanogel can promote the local antigen-presentation to T-cells and represent a promising approach for improving the efficacy of adoptive T-cell therapy for gliomas.

CTIM-08. SAFETY, EFFICACY, AND SURVIVAL RESULTS FROM A PHASE 1 STUDY OF THE ONCOLYTIC ADENOVIRUS DNX-2401 FOLLOWED BY STANDARD OF CARE RADIOTHERAPY FOR NEWLY DIAGNOSED DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG)

Abstract BACKGROUND Diffuse intrinsic pontine glioma (DIPG) is the most lethal pediatric brain tumor. Median overall survival (OS) with standard of care radiation therapy (RT) is approximately 8-10 months and 2-year survival is &amp;lt; 10%. A Phase 1 single-center study was conducted to evaluate the oncolytic adenovirus, DNX-2401 (tasadenoturev), followed by RT for DIPG. METHODS Newly-diagnosed DIPG patients 1-18 years old received a tumor biopsy through the cerebellar peduncle followed by intratumoral injection of 1e10 – 5e10 vp DNX-2401 and conventional RT 1-3 weeks later. RESULTS Subjects were enrolled (n=12) from December 2017 to January 2020 and had a median age of 9 years (range 3-18) and Lansky/Karnofsky performance scores of 90-100 (n=4; 33%) or 70-80 (n=8; 67%). Genetic assessment was completed for 11 subjects (92%) and histone 3 K27M mutations were identified in 10 subjects, including H3F3A (n=8), HIST2H3C (n=1), and HIST1H3B (n=1); 1 subject was H3 wildtype (n=1). TP53 mutations were identified in 5 subjects (42%). DNX-2401 was administered followed by RT (n=11; 92%). No dose-limiting toxicities were observed and the treatment regimen was well-tolerated. The most commonly reported adverse events (≥ 5 subjects), regardless of study drug relationship, include asthenia, headache, vomiting, pyrexia, and neurological deterioration. Three serious adverse events were reported including grade 3 abdominal pain, grade 3 lymphopenia, and grade 3 clinical deterioration. Tumor reductions were reported for 9 subjects (75%), including 2 confirmed (17%) and 2 unconfirmed (17%) responses per RAPNO criteria. As of the data cutoff, median OS is 19.7 months and OS-24 is 32% with follow-up ongoing for 3 subjects (26.9, 25.6, 13.7 months). CONCLUSIONS DNX-2401 followed by RT can be safely administered to DIPG. Survival outcomes are encouraging, thus warranting further evaluation in a Phase 2 study.

PATH-25. H3 K27M-MUTANT DIFFUSE NON-MIDLINE GLIOMA: REPORT OF A CASE WITH EXTENDED FOLLOW-UP

Abstract H3 K27M-mutant diffuse gliomas without midline involvement are extremely rare and their clinical behavior remains elusive due to limited reported follow-up data. We describe an H3 K27M-mutant diffuse non-midline glioma patient with extended follow-up. A 34-year-old woman presented with headache, memory loss, periods of changes in taste and smell, and confusion. Imaging studies revealed an 2.3 cm expansile T2/flair hyperintensity with patchy postcontrast enhancement centered in the left amygdala without associated restricted diffusion and no involvement of the midline structures. The tumor was debulked and consisted of a mitotically active infiltrating astrocytic glioma without tumor necrosis or microvascular proliferation, consistent with anaplastic astrocytoma. Targeted 187-gene neuro-oncology NGS testing detected an H3F3A K27M mutation along with a PTPN11 and a PPM1D mutation. FISH 1p/19q-codeletion testing was negative. MGMT promoter was unmethylated. The patient was treated with chemoradiation with temozolomide for 6 weeks followed by 12 cycles of temozolomide. Four years after initial resection, an area of increased post-contrast enhancement indicating tumor recurrence/progression was noted. Partial resection of the recurrent tumor revealed a mitotically active infiltrating astrocytic glioma with tumor necrosis consistent with glioblastoma. Molecular profiling of the recurrent tumor by the neuro-oncology NGS panel detected similar mutational profile (identical H3F3A K27M and PTPN11 mutation; different PPM1D mutation) with an additional SOS1 mutation. The patient completed 4 cycles of Lomustine and although clinically stable, imaging studies showed slight increase in residual tumor size concerning for tumor progression. Lomustine was discontinued, Bevacizumab therapy was initiated and patient was enrolled in clinical trial (NCT02525692). Despite tumor progression, this patient has had a relatively long disease course (5 years) suggesting that H3 K27M-mutant non-midline diffuse gliomas although molecularly similar, may follow a more favorable clinical course than their midline counterparts possibly due to the hemispheric location, which is more amenable for surgical resection.