Contrast-enhancing Tumor Research Articles

Hypoxia-Responsive Aggregation of Iron Oxide Nanoparticles for T1-to-T2 Switchable Magnetic Resonance Imaging of Tumors

Magnetic resonance imaging (MRI), one of the most general imaging techniques in the clinic, is widely employed for tumor diagnosis with the assistance of contrast agents (CAs). However, currently available CAs in the clinic suffer from shortcomings of a short blood circulation time, lack of specificity to pathological location, insufficient imaging window, and potential biotoxicity of the gadolinium ion. To overcome these problems, on the basis of extremely small iron oxide nanoparticles (ESIONPs), a hypoxia-responsive T1-to-T2 switchable MRI contrast agent was designed and constructed. In detail, polyacrylic acid-modified ESIONPs (ESIONPs-PAA) were first synthesized, and then, nitroimidazole derivatives and cysteine molecules were sequentially coupled on the surface of ESIONPs-PAA to obtain a hypoxia-responsive MRI contrast agent (HR-ESIONPs). Since 2-nitroimidazole and cysteine molecules on the surface of HR-ESIONPs can form an irreversible bond induced by the nitroreductase in the hypoxic tumor microenvironment, monodispersed HR-ESIONPs could transform into the nanocluster form, which can specially provide T2 contrast enhancement. In vitro experiments show that monodispersed HR-ESIONPs could effectively aggregate in the mimical hypoxic environment of tumors and switch from a T1 to T2 contrast agent. Moreover, in vivo experiments further confirm that HR-ESIONPs could effectively accumulate and realize the MRI signal switch from T1 to T2 contrast enhancement in tumors originating from the aggregation of HR-ESIONPs induced by the hypoxic environment, which promotes the diagnostic precision of tumors. Additionally, with the confirmation of favorable biosafety on cells and mice, hypoxia-responsive HR-ESIONPs are potential platforms to improve the diagnostic accuracy and sensitivity of MRI for tumors.

Discriminative MRI Findings of Pituitary Adenomas from Craniopharyngiomas

Purpose: The aim of this study is to determine and define differential magnetic resonance imaging (MRI) findings of pituitary adenomas and craniopharyngiomas. Materials and methods: This retrospective analysis was performed on MR imaging findings of 45 pituitary adenomas and 41 craniopharyngiomas with solid and cystic mixed appearance. MRI findings including shape ovoid, snowman, lobulation, chiasma compression, cavernous sinus invasion, 3rd ventricle compression, calcification, predominant type – cystic vs solid, contrast enhancement patterns – homogenous, reticular and extension were assessed. Results: Among MRI findings superiorly lobulated shape, third ventricle compression and reticular enhancement of solid parts were common in craniopharyngiomas while snowman shape, predominantly solid content, homogenous enhancement of solid parts were compatible with adenomas significantly at p <0.05 for all. Conclusion: Tumor shape and contrast enhancement patterns of solid parts seem discriminative MRI features for pituitary adenoma and craniopharyngiomas.

Can magnetic resonance imaging after cranioplasty using titanium mesh detect brain tumors?

This study determined the dependence of the concentration and position of contrast-enhanced tumors on the radio frequency (RF)-shielding effect of titanium mesh using the contrast-to-noise ratio (CNR) in magnetic resonance imaging (MRI). A phantom was constructed by filling a plastic container with manganese chloride tetrahydrate and agar. Four cellophane cylindrical containers were arranged from the end of the plastic container, and the brain tumor model was filled with gadobutrol diluted with NaCl, with molarity values of 0.2-1.0mmol/L. The titanium mesh board was set on the left side of the phantom. Images were acquired using a 1.5-T MRI as well as two-dimensional spin-echo (2D SE) and three-dimensional fast spoiled gradient echo (3D FSPGR) sequences. CNR was calculated using the signal intensity values of the tumor model, surrounding area of the brain model, and background noise. Furthermore, the fractional change in CNR was calculated using values of CNR with and without the mesh. Moreover, a profile of CNR was created. The fractional change in CNR decreased at the brain tumor positions present near the mesh and at a contrast medium concentration of approximately ≤ 0.5mmol/L in 2D SE and ≤ 0.25mmol/L in 3D FSPGR. According to the CNR profiles, directly under the mesh, almost all contrast concentrations in 2D SE was unrecognizable; however, at a concentration of ≥ 0.5 mmol/L in 3D FSPGR was recognizable.

Evaluation of postcontrast images of intracranial tumors at 7T and 3T MRI: An intra-individual comparison study.

This study aimed to evaluate the diagnostic value of ultrahigh-field magnetic resonance imaging (MRI) for brain tumors in clinical practice. Thirty patients with brain tumors underwent 7- and 3-T MRI. The performance and diagnostic confidence of 7- and 3-T MRI in the visualization of tumor details such as internal structure and feeding artery were evaluated by radiologists. Contrast-enhanced region performance and tumor detail diagnostic confidence score (DCS) were calculated and compared between 7 and 3T using Wilcoxon rank sum test. In 19 with obvious enhancement and 11 cases without obvious enhancement, 7- and 3-T MRI showed similar performance. The tumors' internal structure and feeding artery were more clearly depicted by 7-T MRI (62.2% and 54.4%, respectively) than by 3-T MRI (2.2% and 6.7%, respectively). Furthermore, the mean DCSs of both internal structure and feeding artery were higher at 7T than at 3T (internal structure: 16.29 ± 9.67 vs. -5.79 ± 4.12, p=0.028; feeding artery: 21.96 ± 6.93 vs. 4.46 ± 7.07, p=0.028). The DCS was more significantly improved in the senior radiologist group. Better visualization of brain tumor details and higher tumor detail diagnostic confidence can be obtained with 7-T MRI.

NCOG-11. EXTENT OF RESECTION OF CONTRAST-ENHANCING AND NON-ENHANCING TUMOR: DIFFERENT IMPACTS ON SURVIVAL ACCORDING TO TYPES OF ADULT-TYPE DIFFUSE GLIOMAS IN 2021 WHO CLASSIFICATION

Abstract BACKGROUND To evaluate the impact of extent of resection (EOR) of contrast-enhancing (CE) and nonenhancing (NE) tumors in the types of adult-type diffuse gliomas according to the 2021 WHO classification. METHODS Total 1,196 adult-type diffuse glioma patients diagnosed between 2001 and 2021 from a single institution were enrolled (183 patients with isocitrate dehydrogenase [IDH]-mutant and 1p/19q codeleted oligodendroglioma [herein oligodendroglioma], 211 patients with IDH-mutant astrocytoma, and 802 patients with IDH-wildtype glioblastoma). Analyses were performed within each type to assess predictors of overall survival, including clinical, imaging data, histological grade, O6-methylguanine-methyltransferase (MGMT) promoter methylation status, adjuvant treatment, and EOR of CE and NE tumors. Subgroup analyses were performed in patients with CE tumor. RESULTS Among 1,196 patients, 926 (77.4%) patients had CE tumors. In oligodendrogliomas, gross total removal (GTR) of CE tumor was associated with survival (hazard ratio [HR]=0.09, P< 0.001), whereas GTR of NE tumor was not associated with survival (HR=0.41, P=0.088). In 81 (43.3%) oligodendroglioma patients with CE tumor, GTR of CE tumor was the only independent predictor of survival (HR=0.20, P=0.092) in multivariable analysis. GTR of CE and NE tumors was independently associated with better survival in IDH-mutant astrocytoma and IDH-wildtype glioblastoma (all Ps< 0.05). CONCLUSIONS GTR of both CE and NE tumors may significantly improve survival within all types of adult-type diffuse gliomas except oligodendrogliomas. In oligodendrogliomas, the EOR of CE tumor may be crucial in survival; aggressive GTR of NE tumor may be unnecessary, whereas GTR of the CE tumor is recommended.

SURG-19. PROGNOSTIC VALIDATION OF A NEW CLASSIFICATION SYSTEM FOR EXTENT OF RESECTION IN GLIOBLASTOMA: A REPORT OF THE RANO RESECT GROUP

Abstract BACKGROUND Terminology to describe extent of resection in glioblastoma is inconsistent across clinical trials. A surgical classification system was previously proposed based upon residual contrast-enhancing (CE) tumor. We aimed to (I) explore the prognostic utility of the classification system and (II) define how much removed non-CE tumor translates into a survival benefit. METHODS The international RANO resect group retrospectively searched the databases from seven neuro-oncological centers in the USA and Europe for patients with newly diagnosed glioblastoma per WHO 2021 classification. Clinical and volumetric information from pre- and post-operative MRI were collected. RESULTS We collected 1021 patients with newly diagnosed glioblastoma, including 1008 IDHwt patients. 744 IDHwt glioblastomas were treated with radiochemotherapy per EORTC 26981/22981 (TMZ/RT→TMZ) following surgery. Among such homogenously treated patients, lower absolute residual tumor volumes (in cm3) were favorably associated with outcome: patients with ‘maximal CE resection’ (class 2) had superior outcome compared to patients with ‘submaximal CE resection’ (class 3) or ‘biopsy’ (class 4) (median OS: 19 versus 15 versus 10 months; p=0.001). Extensive resection of non-CE tumor (≤ 5 cm3 residual non-CE tumor) provided an additional survival benefit in patients with complete CE resection, thus defining class 1 (‘supramaximal CE resection’) (median OS: 24 versus 19 months; p=0.008). The prognostic value of the resection classes was retained on multivariate analysis when adjusting for molecular and clinical markers including MGMT promotor status. Relative tumor reduction (in percentage) was not prognostic for outcome on multivariate analysis, and inter-rater agreement for CE and non-CE tumor on post-operative MRI was sufficient. CONCLUSION The proposed “RANO categories for extent of resection in glioblastoma” are highly prognostic and may serve for stratification of clinical trials. Removal of non-CE tumor beyond the CE tumor borders translates into additional survival benefit, providing a rationale to explicitly denominate such a ‘supramaximal CE resection’.

EXTH-28. INTRATUMORAL HETEROGENEITY OF THERAPEUTIC VULNERABILITIES ACROSS ENHANCING AND NON-ENHANCING TUMOR COMPONENTS OF GLIOBLASTOMA: A PARADIGM-SHIFTING PERSONALIZED MEDICINE APPROACH

Abstract Glioblastoma (GBM) is the most aggressive adult brain tumor with no effective therapy. Despite advances on its molecular characterization, targeted therapeutics remain out of reach. This lack-of-progress is largely attributed to molecular and spatial heterogeneity and absence of clinically applicable models to guide patient care. Moreover, as standard surgical resection is aimed at contrast-enhancing (CE) tumor, the molecular landscape and treatment response of the remaining non-contrast enhancing (nCE) component is largely unknown despite its active role in tumor progression and local recurrence. Here, we aimed to identify the functional impact of tumor heterogeneity and to explore therapeutic vulnerabilities of both CE and nCE components. Four tumor regions (two CE and two nCE) from each of five GBM patients were collected under neuronavigation. The resulting tissue was subjected to generation of 3D tumor models (a brain tumor initiating-enriched cell line and a spheroid-based mcancer model) with comparable success in both CE and nCE samples. A panel of 25 brain penetrant drugs (alone and in combination) targeting GBM drivers (i.e. RTK/Ras/PI3K, RB/cell cycle, p53/apoptosis, DNA damage repair, transcription addiction) was developed and used to test for therapeutic vulnerabilities. From each tumor region, 4.5 ± 3.7 (average ± SD) different targeting strategies were identified exhibiting at least 70% growth inhibition at Cmax. Drug response heterogeneity was relatively rare, varied among cases, and was independent of tumor enhancement status. To our knowledge, this is the first study to systemically assess treatment response from both CE and nCE patient-derived GBM models. Ongoing studies include comprehensive genome and transcriptome profiling and pathway analysis from these different tumor regions. We postulate that interrogation of molecular landscapes and vulnerability profiles of both CE and nCE tumor regions, will enable us to personalize and prioritize effective targeted interventions for GBM treatment.

EXTH-65. SYNERGISTIC ONCOLYTIC EFFECTS OF TEMOZOLOMIDE AND ONCOMAGNETIC THERAPIES IN GLIOBLASTOMA

Abstract The noninvasive Oncomagnetic device developed in our laboratory selectively kills glioblastoma (GBM) and other cancer cells while sparing normal developing neurons and astrocytes in vitro. We have reported that brief 2 – 6 h of daily Oncomagnetic brain stimulation causes >30% reduction of contrast-enhanced tumor (CET) volume in an end-stage recurrent GBM patient after a ~30-day treatment. We have evidence that the spinning oscillating magnetic fields (sOMF) generated by this device disrupts electron transport in the mitochondrial respiratory chain, at least in part by inhibiting the activity of Complex II succinate dehydrogenase, leading to a marked increase in reactive oxygen species (ROS) and consequent cancer cell death. Here, we further studied the cellular effects of sOMF treatment alone and in combination with Temozolomide (TMZ) on GBM cell lines with other methods and investigated the response to Oncomagnetic monotherapy (OMT) in a mouse GBM model. We treated LN229 and U87 GBM cells with sOMF with and without a sub-therapeutic dose of TMZ. To study the anticancer effect of sOMF in vivo, we developed syngeneic GBM tumors in BALB/c mice by stereotactic intracranial injection of GL261WT cells. Our results show that cytotoxic effects of sOMF or TMZ alone, as measured by the MTT assay and reduced cell survival, are significantly potentiated by combining the two treatments. OMT of tumor-bearing mice using a whole-body sOMF stimulation method causes substantial retardation of tumor growth and reduction of the CET volume in 9.4 T MRI scans. To study the molecular pathways involved in the treatment response we are mapping alterations in various key biomarkers in treated tumor tissues and comparing them with those in untreated controls. These experiments will unravel the molecular mechanism of action underlying the response to OMT in GBM and help develop a sound rationale for an effective therapeutic protocol.

DDEL-11. DETERMINING THE DOSE OF REGADENOSON MOST LIKELY TO TRANSIENTLY ALTER THE INTEGRITY OF THE BLOOD-BRAIN BARRIER IN PATIENTS WITH GLIOMAS

Abstract BACKGROUND The blood brain barrier (BBB) is a major obstacle to the delivery of chemotherapy to the CNS. Regadenoson is an FDA approved adenosine A2 agonist used for cardiac stress tests. In murine models, it transiently increases BBB permeability to a 70KD dextran. This multi-institutional, NIH funded, Adult Brain Tumor Consortium trial was designed to discover a dose of regadenoson that substantially increases vascular permeability in normal appearing white matter (NAWM) where drug delivery is particularly challenging. METHODS Adults ages 18-45 with supratentorial gliomas at low-risk for regadenoson complications were recruited (n = 7). One patient was treated at each of seven dose levels (from 0.05 to 1.4 mg) that are known to be safe in humans. The primary outcome measure is change in vascular permeability via dynamic contrast enhanced (DCE) perfusion MRI estimates of Ktrans. The primary outcome measure was a 10-fold higher Ktrans in NAWM than reported in literature (Ktrans > 0.04 min-1). Contrast-enhanced T1 subtraction map estimates of change in contrast enhancement and other measurements in normal brain and non-enhancing tumor were quantified. RESULTS Ktrans measures in NAWM averaged 1.13x10-3 ± 0.44x10-3 (SEM) min-1, lower than the target of 0.04 min-1. Normalized, contrast enhanced T1-weighted MR signal intensity in NAWM increased an average of 74.0 ± 22.4% min-1 (SEM) min-1, which was significantly higher than zero (P = 0.0163). Data available from this limited sample failed to meet the target goal in Ktrans increase or change in contrast enhancing signal intensity. CONCLUSION Administration of regadenoson at seven different doses did not significantly elevate Ktrans for gadolinium in NAWM. This data suggests that single doses of regadenoson are unlikely to substantially increase the delivery of therapeutic agents in non-enhancing brain tissue. This trial design is appropriate for further human testing of other regadenoson schedules and other novel approaches aimed at transiently modifying BBB permeability.

Alterations in white matter fiber density associated with structural MRI and metabolic PET lesions following multimodal therapy in glioma patients.

In glioma patients, multimodality therapy and recurrent tumor can lead to structural brain tissue damage characterized by pathologic findings in MR and PET imaging. However, little is known about the impact of different types of damage on the fiber architecture of the affected white matter. This study included 121 pretreated patients (median age, 52 years; ECOG performance score, 0 in 48%, 1-2 in 51%) with histomolecularly characterized glioma (WHO grade IV glioblastoma, n=81; WHO grade III anaplastic astrocytoma, n=28; WHO grade III anaplastic oligodendroglioma, n=12), who had a resection, radiotherapy, alkylating chemotherapy, or combinations thereof. After a median follow-up time of 14 months (range, 1-214 months), anatomic MR and O-(2-[18F]fluoroethyl)-L-tyrosine (FET) PET images were acquired on a 3T hybrid PET/MR scanner. Post-therapeutic findings comprised resection cavities, regions with contrast enhancement or increased FET uptake and T2/FLAIR hyperintensities. Local fiber density was determined from high angular-resolution diffusion-weighted imaging and advanced tractography methods. A cohort of 121 healthy subjects selected from the 1000BRAINS study matched for age, gender and education served as a control group. Lesion types differed in both affected tissue volumes and relative fiber densities compared to control values (resection cavities: median volume 20.9 mL, fiber density 16% of controls; contrast-enhanced lesions: 7.9 mL, 43%; FET uptake areas: 30.3 mL, 49%; T2/FLAIR hyperintensities: 53.4 mL, 57%, p<0.001). In T2/FLAIR-hyperintense lesions caused by peritumoral edema due to recurrent glioma (n=27), relative fiber density was as low as in lesions associated with radiation-induced gliosis (n=13, 48% vs. 53%, p=0.17). In regions with pathologically increased FET uptake, local fiber density was inversely related (p=0.005) to the extent of uptake. Total fiber loss associated with contrast-enhanced lesions (p=0.006) and T2/FLAIR hyperintense lesions (p=0.013) had a significant impact on overall ECOG score. These results suggest that apart from resection cavities, reduction in local fiber density is greatest in contrast-enhancing recurrent tumors, but total fiber loss induced by edema or gliosis has an equal detrimental effect on the patients' performance status due to the larger volume affected.

TMIC-77. SINGLE-CELL CHARACTERIZATION OF HUMAN GBM REVEALS REGIONAL DIFFERENCES IN TUMOR-INFILTRATING LEUKOCYTE ACTIVATION

Abstract Clinical trials of systemic T cell checkpoint blockade in GBM patients showed only disappointing results. This may be attributed in part to the immunosuppressive components of the GBM immune tumor microenvironment (iTME). Therefore, major efforts have been undertaken to describe the GBM iTME on a single cell level. However, human data on the composition of the iTME in different tumor regions (contrast enhancing tumor center versus peripheral infiltration zone) remain scarce. Here, we performed high-depth single-cell RNA sequencing (scRNAseq) on patient-matched biopsies from the tumor center and the peripheral infiltration zone of five primary GBM patients. Additionally, peripheral blood mononuclear cells (PBMC) of the same patients were included in the scRNAseq analysis to explore the transcriptional changes occurring during tumor infiltration of circulating immune cells. Through analysis of &amp;gt; 45’000 cells, we revealed a distinct regional transcriptional profile of microglia (MG) and monocyte-derived macrophages (MdM), a non-reactive/exhausted MG subcluster in the GBM iTME and an impaired interferon-response signature in the peripheral cytotoxic cell compartment. Comparing CD8+ T-cells from the tumor periphery to PBMC-derived CD8+ T-cells of the same patient revealed a CX3CR1+ CD8+ T-cell population with effector memory phenotype which is enriched in the PBMC but lacking in the tumor periphery. Peripheral CD8+ T-cells were mainly composed of tissue-resident memory CD8+ T-cells with exhausted effector functions. Our analysis provides a large-scale dissection of GBM-associated cell types complemented by patient-matched PBMCs, serving as a high dimensional reference map of the human GBM iTME.

QLTI-01. THE EFFECT OF COMPLETE RESECTION OF CONTRAST-ENHANCING TUMOR ON SURVIVAL IN PATIENTS WITH GLIOBLASTOMA OVER A 16-YEAR PERIOD IN A GEOGRAPHICALLY DEFINED POPULATION

Abstract INTRODUCTION The median survival for patients with glioblastoma is less than one year, and survival beyond five years is rare. Radiotherapy combined with chemotherapy has improved survival since its introduction in 2005. No new treatment modalities have been widely adopted after this, but treatment development has focused on achieving maximal resection and the introduction of coordinated clinical care pathways. We hypothesize that these changes in approach have resulted in an improved survival in surgically treated patients. METHODS Retrospective analysis of a prospectively collected database in the adult population (2.4 million habitants) of South-Eastern Norway. Patients were divided in three periods; radiotherapy- (2003-2005), temozolomide- (2006-2012), and resection focused-period (2013-2019). Patients were also stratified according to age and grade of resection. Relative survival, Cox hazard-ratio, 3- and 5- year survival were calculated. RESULTS We identified 1663 surgically treated glioblastoma patients eligible for the study. The median overall survival was 11.4 months. Complete resection of contrast-enhanced tumor (CRCET) was achieved in 387 (23.2%) patients. The frequency of CRCET increased during the observation time (32 - 116 - 239), but there was no increase in reoperation rates (13%). Significant improvement between the last period and the first two periods was observed (12.3 vs. 10.5 months, p &amp;lt; 0.006), with a significant increase in 3- and 5- year survival probability between the first two groups (p = 0.01). No difference was found in median survival in CRCET among periods. Patients with CRCET demonstrated significantly longer median survival than patients with non-CRCET (16.1 vs. 10.8 months; p &amp;lt; 0.001). Incidence in the elder group increased from 2.6 to 13.2 per 100,000 habitants, and median survival doubled when CRT was achieved. CONCLUSIONS There is an increase in median survival, 3- and 5- year survival probability when comparing time-periods. We suggest this survival benefit is related to improved CRCET rates.

CTNI-48. TRIAL UPDATE -RESULTS OF A PHASE I WINDOW OF OPPORTUNITY TRIAL EVALUATING A FIRST-IN-CLASS CD29 INHIBITOR, OS2966, IN RECURRENT HIGH-GRADE GLIOMA

Abstract BACKGROUND OS2966 is a first-in-class, humanized, and deimmunized anti-CD29 (β1integrin) monoclonal antibody. CD29 is a mechanosignaling receptor prominently upregulated in glioblastoma. Preclinical studies in mice and non-human primates have demonstrated safety and encouraging efficacy. A phase I clinical trial was therefore initiated to evaluate the safety and feasibility of delivering OS2966 directly to the site of disease via convection-enhanced delivery (CED) in recurrent high-grade glioma patients. METHODS This study employs a 2-part design: In part 1, patients undergo stereotactic tumor biopsy followed by placement of a CED catheter(s) for delivery of OS2966 to the bulk contrast-enhancing tumor. Subsequently, in part 2, patients undergo a clinically-indicated tumor resection followed by placement of CED catheter(s) and delivery of OS2966 to the surrounding tumor-infiltrated brain. Co-convection of gadolinium enables real-time monitoring of therapeutic delivery. A concentration-based accelerated titration design is utilized for dose escalation. Given availability of pre and post-infusion samples, pharmacodynamic data will be analyzed to explore mechanism of action of OS2966. RESULTS Four patients have completed treatment in both study parts. No dose-limiting toxicity or adverse events related to treatment with OS2966 or CED catheter placement have been reported at the first 3 dose levels (ie, doses up to 0.6 mg/mL). For the four patients treated an average of 4.2 mL and 3.2 mL were infused in study parts 1 and 2 respectively. The Vd/Vi ratio ranged from 0.6 to 1.6 in part 1, and from 2.0 to 4.3 in Study Part 2. Analysis of tissue samples collected during the trial has demonstrated decreased VEGF expression post-treatment, with preinfusion samples showing &amp;gt; 50% VEGF expression and post-infusion samples showing 10% expression. Additional pharmacodynamic analysis via tissue-level biomarkers is ongoing and will be presented. CONCLUSION Initial data demonstrate the safety and feasibility of direct intracranial delivery of OS2966.

INNV-12. REPRODUCIBLE REDUCTIONS OF CONTRAST-ENHANCED TUMOR VOLUMES IN TWO END-STAGE RECURRENT GLIOBLASTOMA PATIENTS WITH IN-HOME ONCOMAGNETIC MONOTHERAPY

Abstract A spinning oscillating magnetic field-generating device called the Oncomagnetic device selectively kills glioblastoma (GBM) cells. It produced &amp;gt; 30% shrinkage of a recurrent GBM tumor in an end-stage patient after &amp;lt; 5 weeks of Oncomagnetic treatment (OMT). We have now reproduced this treatment response with additional insights into device effectiveness in two more such patients undergoing compassionate use OMT. We provided OMT to a 55-year-old man with massive recurrent tumor regrowth and a 79-year-old woman with multifocal recurrent GBM showing rapid progression, with leptomeningeal spread in both cases. Both had failed standard of care chemoradiotherapy and in the former case had not tolerated Optune treatment. They received one 2-hour, two 2-hour and three 2-hour OMTs per day in the clinic on the first three days under the supervision of the treating physician. 3 2-hour daily treatments were continued subsequently at home. The first patient received a steroid drug along with OMT to control cerebral edema from the start. In the second patient it was added after 14 days while also reducing OMT to 2 hours a day because of significant evidence of edema. MRI scans were done periodically to assess the treatment response. Both patients tolerated OMT well with no serious adverse effects – for 7 months in the first patient, including four 2-hour treatments for the last 5 months, and for 2 months in the second patient. Their last MRI scans at Day 146 and Day 42 showed &amp;gt; 35% and &amp;gt; 91% reduction, respectively, in contrast-enhanced tumor volume compared to pre-OMT scans. A modified treatment response assessment mapping analysis showed substantial reductions in both necrotic and active tumor volumes. These findings strongly support the observations in our published single patient case report and provide firm grounds for proposing in-home OMT monotherapy as a safe and effective noninvasive treatment for GBM.

BIOM-33. TEMPORAL HETEROGENEITY OF DNA METHYLATION SUBCLASSES BETWEEN MATCHED NEWLY DIAGNOSED AND RECURRENT IDH-WILDTYPE GLIOBLASTOMA

Abstract Spatiotemporal heterogeneity is a major factor contributing to the devastating prognosis of isocitrate-dehydrogenase (IDH)-wildtype glioblastoma. Genome-wide DNA methylation profiling allows the stratification into several DNA methylation subgroups of IDH-wildtype glioblastoma, which were shown to have a spatial heterogeneity in newly diagnosed tumors. However, the temporal heterogeneity and its clinical relevance of DNA methylation subgroups remains inconclusive. Tumor tissue obtained from first and recurrence surgery of 31 patients diagnosed with IDH-wildtype glioblastoma was subjected to DNA methylation profiling. DNA methylation profiles were analyzed for temporal heterogeneity and correlated with clinical data, survival outcome and copy number variations. In addition, deconvolution of immune cells and unsupervised hierarchical clustering using pairwise Pearson correlation coefficients of the 10.000 most variable CpG features was performed. Of all patients with matched tumor tissue, 4 (12.9%) patients had a non-matching brain tumor classifier output at recurrence. Within the remaining 27 patients, a transition of the dominant DNA methylation subclass was observed in 8 (29.6%) glioblastomas with a most frequent transition to the mesenchymal subclass (62.5%). A subclass transition was more likely after incomplete removal of contrast-enhanced tumor parts at first surgery (p = 0.04). Tumor location, adjuvant treatment, and time between primary and recurrence surgery did not influence the transition. Immune cell proportions from deconvolution data, tumor purity or specific CpG sites were not correlated with a subclass transition. Survival analyses revealed a comparable outcome for patients with or without subclass transition. Our findings demonstrate the temporal heterogeneity of DNA methylation subclasses in 29.6% of IDH-wildtype glioblastoma. We identified clinical factors and showed that a subclass transition did not impact the survival outcome. However, a possible DNA methylation subclass transition must be taken into consideration for future targeted therapies at recurrence.

MRI Changes in Failed Radiosurgery for Vestibular Schwannomas

Introduction: Radiosurgery is now a recognized treatment of vestibular schwannoma (VS); however, radiosurgical irradiation sometimes fails to stop tumor growth in the long term. Some changes in MR imaging after radiosurgery that are supposed to be related to permanent tumor control may be observed in patients with failed treatment. The objective of the present study was to evaluate the MRI changes observed early after radiosurgery in a cohort of patients with failed radiosurgery for VS. Methods: From a large series of VS treated radiosurgically for 15 years, we reviewed the follow-up MRI data in a subgroup of VS that presented obvious treatment failure. T1-weighted MR imaging with standard timing of gadolinium injection was applied for image acquisition during the radiosurgical procedure and all follow-up MR imaging. Evolution of tumor volume and contrast enhancement were assessed on 3D-co-registered MRI. Results: Twenty-nine of 728 patients (4%) were retreated for the same VS after >2 years (median 3.14 years, range 2.04–9.47) following initial radiosurgical treatment. The median tumor volume was 0.94 cc at first radiosurgical treatment and 2.19 cc at retreatment. Fourteen patients (48.3%) had continuous increase in tumor volume. For 10 patients (34.5%), the tumor volume reduced significantly after irradiation before it increased again. Four patients (13.8%) showed a transient increase in tumor volume after irradiation, followed by significant volume reduction, then a very significant tumor regrowth. A significant loss of contrast enhancement at the center of the tumor was observed for 25 patients (86.2%); full recovery of contrast enhancement of the tumor was observed for 23 patients. Discussion/Conclusion: Tumor volume reduction and central loss of contrast enhancement of the tumor are MRI changes frequently observed during follow-up of VS treated radiosurgically even in patients with failed long-term tumor control and may therefore not be considered as signs of successful response of the tumor to the radiosurgical treatment.

CHITOSAN NANOBUBBLES DEVELOPMENT AND EVALUATION FOR THE DELIVERY OF SUNITINIB-AN ANTICANCER AGENT

Objective: In the current study, we introduced a novel method for creating Sunitinib nanobubbles by incorporating it into chitosan-shelled nanobubbles. Methods: The Design Expert® programme randomly assigned around 13 experiments, and multiple regression analysis was used to statistically examine the data. The effect of the amount of sunitinib, amount of chitosan, amount of Epikuron 200, amount of palmitic acid and stirring speed, on percent encapsulation efficiency and drug load while maintain minimum particle size of nanobubbles as considered through a definitive screening plan. By placing limitations on the response parameters, the optimum formulation was created using a numerical optimization approach. The three improved formulations (Batch1 through Batch3) were assessed. Results: The findings show that the nanobubbles particle size of 78.56-82.42 nm with an encapsulation efficiency of 68.48-69.56 % and loading capacity of 23.88-25.02%. The quantity of sunitinib released from nanobubbles was much larger (96.52 percent) than that from the sunitinib solution within 24 h, according to an in vitro release profile of the medication using ultrasonography. The hemolytic activity of the blank nanobubbles and sunitinib-loaded nanobubbles was measured to assess their safety up to a concentration of 10 mg/ml. With erythrocytes, drug-loaded nanobubbles had a good safety profile. FTIR, DSC studies indicated no chemical interactions, TEM images revealed nanobubbles size of 70-100 nm and stability studies shows no significant changes. Conclusion: For contrast-enhanced tumour imaging and subsequent therapeutic administration, nanobubbles were found to be superior.

A Neutral and Stable Macrocyclic Mn(II) Complex for MRI Tumor Visualization.

A stable and inert amphiphilic Mn(II) complex based on a bisamide derivative of 1,4-DO2A (DO2A=tetraazacyclododecane-1,4-diacetic acid) was synthesized and its 1 H NMR relaxometric behavior was investigated as a function of the magnetic field strength, pH and temperature. The interaction with human serum albumin (HSA) was also studied via relaxometry showing a good relaxivity enhancement at low field (at 1T and 298 K the relaxivity increases from 4.5 mM-1 s-1 of the Mn(II)-complex to 14.0 mM-1 s-1 of the complex-HSA supramolecular adduct). In vivo biodistribution and MRI studies highlighted a rapid and mixed renal/liver elimination without spleen accumulation from healthy mice and good contrast enhancing properties in a breast tumor murine model. A comparison with a clinically approved Gd(III) agent (GdBOPTA, Multihance®) underlined that the proposed Mn(II) contrast agent gave comparable tumor contrast enhancement up to 3 hours post-injection.

Patterns of Treatment Failure in PCNSL

<h3>Purpose/Objective(s)</h3> Primary CNS Lymphoma (PCNSL) is a rare and often fatal disease. Despite varied combinations of therapy with a backbone of high-dose methotrexate (HD-MTX), there remains no clear standard of care and treatment failure is a persistent challenge. This analysis evaluates factors that affect local disease control and patterns of failure. <h3>Materials/Methods</h3> Retrospective review of 95 consecutive patients with PCNSL pathologically confirmed from 2002 and 2021. The primary endpoints were Local Failure (LF) and pattern of first failure (distant only vs local). Univariate (UVA) and multivariate analyses (MVA) with backward selection at alpha of 0.2, Log-rank test and Cox proportional hazard models were used for time to event endpoints and associations with age, Karnofsky performance status (KPS; ≥70 vs <70), use of upfront WBRT, number of cycles of HD-MTX (≥6 vs 0-5), 1^st line chemo agents, type of surgery, and size of contrast-enhancing lesion(s) (≥14cc vs <14 cc). <h3>Results</h3> Most patients had KPS ≥70 (64.2%), were HIV negative (89.5%), and had no history of solid organ transplant (95.8%). Diagnosis was made by biopsy (73.7%) or resection (26.3%). 54.3% had <14 cc contrast-enhancing tumor volume (overall median 12.6 cc, range 0.5 - 67.8 cc). Of the 62 patients treated first line with at least 1 cycle of HD-MTX, 61.3% had HD-MTX + Rituximab (R). Of the 60 patients with evaluable CSF, 30.0% had positive cytology. IT chemotherapy (ITc) was administered to 12 patients (cytology positive for 5, negative for 4, and unknown for 3). WBRT for consolidation after chemotherapy used for 3 patients and as monotherapy for 9 patients with poor KPS. At 2-years, OS was 50%, PFS was 39%, and LF was 27%. For patients with progression (n=29), 7 had distant only progression while 5 had local and distant progression and 17 had local only progression. LF was numerically higher in patients with ≥14 cc tumors (2-yr LF 26% vs 42%, p=0.43). On MVA, hazard of LF was significantly associated with age (HR 1.08 per yr, 95% CI: 1.02-1.16, p=0.02), KPS (HR 0.10, 95% CI: 0.01-0.65, p=0.016), completion of at least 6 cycles HD-MTX (HR 0.10, 95% CI 0.03-0.34, p<0.01), and use of ITc (HR 0.03, 95% CI: 0.00-0.32, p<0.01). There were no significant associations with upfront WBRT (p=0.37), use of HD-MTX + R (p = 0.12), or type of surgery (p=0.94). On UVA, distant first failure trended to be significantly associated with age (p=0.06), ITc use (p=0.07), and size of lesion(s) (p=0.08). On MVA, distant only first failure was significantly associated with age (OR 0.91 per year, 95% CI: 0.83-0.99, p=0.04). <h3>Conclusion</h3> The majority of treatment failures were local only. LF of PCNSL was associated with not completing induction HD-MTX and not using ITc. There was no association with LF or type of first failure and use of WBRT or more aggressive surgery. Larger tumors trended to fail locally warranting further investigation as local disease can be devastating.

Differentiation of Intracerebral Tumor Entities with Quantitative Contrast Attenuation and Iodine Mapping in Dual-Layer Computed Tomography.

Purpose: To investigate if quantitative contrast enhancement and iodine mapping of common brain tumor (BT) entities may correctly differentiate between tumor etiologies in standardized stereotactic CT protocols. Material and Methods: A retrospective monocentric study of 139 consecutive standardized dual-layer dual-energy CT (dlDECT) scans conducted prior to the stereotactic needle biopsy of untreated primary brain tumor lesions. Attenuation of contrast-enhancing BT was derived from polyenergetic images as well as spectral iodine density maps (IDM) and their contrast-to-noise-ratios (CNR) were determined using ROI measures in contrast-enhancing BT and healthy contralateral white matter. The measures were correlated to histopathology regarding tumor entity, isocitrate dehydrogenase (IDH) and MGMT mutation status. Results: The cohort included 52 female and 76 male patients, mean age of 59.4 (±17.1) years. Brain lymphomas showed the highest attenuation (IDM CNR 3.28 ± 1,23), significantly higher than glioblastoma (2.37 ± 1.55, p < 0.005) and metastases (1.95 ± 1.14, p < 0.02), while the differences between glioblastomas and metastases were not significant. These strongly enhancing lesions differed from oligodendroglioma and astrocytoma (Grade II and III) that showed IDM CNR in the range of 1.22–1.27 (±0.45–0.82). Conventional attenuation measurements in DLCT data performed equally or slightly superior to iodine density measurements. Conclusion: Quantitative attenuation and iodine density measurements of contrast-enhancing brain tumors are feasible imaging biomarkers for the discrimination of cerebral tumor lesions but not specifically for single tumor entities. CNR based on simple HU measurements performed equally or slightly superior to iodine quantification.