Brain Re-Irradiation Or Chemotherapy: a phase II randomised trial of re-irradiation and chemotherapy in patients with recurrent glioblastoma (BRIOChe) - protocol for a multi-centre open-label randomised trial

INTRODUCTION

Glioblastoma (GBM) is the most common adult primary malignant brain tumour. The condition is incurable and, despite aggressive treatment at first presentation, almost all tumours recur after a median of 7 months. The aim of treatment at recurrence is to prolong survival and maintain health-related quality of life (HRQoL). Chemotherapy is typically employed for recurrent GBM, often using nitrosourea-based regimens. However, efficacy is limited, with reported median survivals between 5 and 9 months from recurrence. Although less commonly used in the UK, there is growing evidence that re-irradiation may produce survival outcomes at least similar to nitrosourea-based chemotherapy. However, there remains uncertainty as to the optimum approach and there is a paucity of available data, especially with regards to HRQoL. Brain Re-Irradiation Or Chemotherapy (BRIOChe) aims to assess re-irradiation, as an acceptable treatment option for recurrent IDH-wild-type GBM.

METHODS AND ANALYSIS

BRIOChe is a phase II, multi-centre, open-label, randomised trial in patients with recurrent GBM. The trial uses Sargent's three-outcome design and will recruit approximately 55 participants from 10 to 15 UK radiotherapy sites, allocated (2:1) to receive re-irradiation (35 Gy in 10 daily fractions) or nitrosourea-based chemotherapy (up to six, 6-weekly cycles). The primary endpoint is overall survival rate for re-irradiation patients at 9 months. There will be no formal statistical comparison between treatment arms for the decision-making primary analysis. The chemotherapy arm will be used for calibration purposes, to collect concurrent data to aid interpretation of results. Secondary outcomes include HRQoL, dexamethasone requirement, anti-epileptic drug requirement, radiological response, treatment compliance, acute and late toxicities, progression-free survival.

ETHICS AND DISSEMINATION

BRIOChe obtained ethical approval from Office for Research Ethics Committees Northern Ireland (reference no. 20/NI/0070). Final trial results will be published in peer-reviewed journals and adhere to the ICMJE guidelines.

TRIAL REGISTRATION NUMBER

ISRCTN60524.

Imaging Spectrum of the Developing Glioblastoma: A Cross-Sectional Observation Study

Glioblastoma (GBM) has the typical radiological appearance (TRA) of a centrally necrotic, peripherally enhancing tumor with surrounding edema. The objective of this study was to determine whether the developing GBM displays a spectrum of imaging changes detectable on routine clinical imaging prior to TRA GBM. Patients with pre-operative imaging diagnosed with GBM (1 January 2014-31 March 2022) were identified from a neuroscience center. The imaging was reviewed by an experienced neuroradiologist. Imaging patterns preceding TRA GBM were analyzed. A total of 76 out of 555 (14%) patients had imaging preceding TRA GBM, 57 had solitary lesions, and 19 had multiple lesions (total = 84 lesions). Here, 83% of the lesions had cortical or cortical/subcortical locations. The earliest imaging features for 84 lesions were T2 hyperintensity/CT low density (n = 18), CT hyperdensity (n = 51), and T2 iso-intensity (n = 15). Lesions initially showing T2 hyperintensity/CT low density later showed T2 iso-intensity. When CT and MRI were available, all CT hyperdense lesions showed T2 iso-intensity, reduced diffusivity, and the following enhancement patterns: nodular 35%, solid 29%, none 26%, and patchy peripheral 10%. The mean time to develop TRA GBM from T2 hyperintensity was 140 days and from CT hyperdensity was 69 days. This research suggests that the developing GBM shows a spectrum of imaging features, progressing through T2 hyperintensity to CT hyperdensity, T2 iso-intensity, reduced diffusivity, and variable enhancement to TRA GBM. Red flags for non-TRA GBM lesions are cortical/subcortical CT hyperdense/T2 iso-intense/low ADC. Future research correlating this imaging spectrum with pathophysiology may provide insight into GBM growth patterns.

QOL-19. RETURNING TO WORK AFTER A BRAIN TUMOUR – “I THOUGHT I WOULD BE BACK AT WORK THE NEXT WEEK, HOW WRONG I WAS!”

BACKGROUND

Returning to work is important for patients' and their families’ well-being, financial circumstances and quality of life. Side-effects of brain tumour (BT) treatment or clinical deterioration from BT progression often causes temporary or permanent inability to work. Aim: To explore the occupational expectations, experiences and satisfaction of BT patients (and their caregivers) following diagnosis/treatment.

METHODS

Qualitative semi-structured interviews were conducted with adults diagnosed with a primary BT, in employment/self-employed before diagnosis, currently in follow-up care; and their caregivers. Purposive sampling ensured a mixed BT sample. Participants were recruited from two UK tertiary referral hospitals. Data collection and thematic analysis are ongoing and will be completed by August 2022.

RESULTS

To date, 17 interviews (13 patient/4 caregiver) have taken place (59% female, aged 26-73,M= 43). Early findings: 1) Managing expectations: Patients underestimated the impact of surgery and how long it would take to return to work (if they had). Many would have liked more information prior to treatment about potential side-effects (e.g., extreme fatigue). 2) Prior financial support: Most patients suffered financially, often resulting in returning to work before they felt ready. Patients wanted more information prior to treatment about financial support. 3) Ongoing communication: Employers who were emotionally and practically supportive throughout the BT trajectory were highly valued. Some interviewees believed their employers needed to receive better education about BTs. 4) Flexible working: Patients returning to work with enhanced employer support (e.g., reduced hours, working from home and lighter duties) were more satisfied. 5) Better caregiver support: Many caregivers were unsupported by their employers to take carer leave, some worked more to support the family financially.

CONCLUSIONS

Preliminary findings offer novel data in an under-researched area. More knowledge around the experiences, barriers and facilitators influencing patients’ return to work will allow the planning of tailored occupational support and resources.

QOL-11. COMMUNICATION IN THE CONTEXT OF GLIOBLASTOMA TREATMENT: WHAT MATTERS MOST

BACKGROUND

Given the poor prognosis of glioblastoma, it is critical that the benefits and burdens of treatments are clearly discussed with patients and family caregivers. We investigated experiences and preferences around glioblastoma treatment communication in patients, caregivers, and healthcare professionals (HCPs).

METHODS

Semi-structured qualitative interviews were conducted with adult glioblastoma patients, their caregivers, and HCPs. Purposive sampling was used to capture views across the entire disease trajectory and different specialties. Interviews were recorded, transcribed verbatim, and analysed thematically.

RESULTS

In total, 15 patients, 13 caregivers (in N=12 individual and N=8 dyadic interviews), and five HCPs participated (N=5 individual interviews). Four main themes were identified. 1) Communication practice and preferences. Risks and side-effects of anti-tumour treatments were explained clearly, with information layered and revisited frequently to aid understanding. Treatment was often understood to be ‘the only option’, particularly at recurrence. Understanding the impact of side-effects on daily life could be enhanced, including those from supportive medication (e.g., corticosteroids); alongside more proactive communication about support services. 2) What matters most. Patients/caregivers valued being well-supported by a trusted treatment team, feeling involved, having a sense of control, and quality of life. HCPs similarly highlighted trust, maintaining independence and quality of life, and emotional support as key. 3) Decision-making. With limited treatment options, trust and control are crucial in decision-making among patients, caregivers, and HCPs. While patients ultimately prefer to follow HCP advice they want to be involved, consider all alternatives, and voice what matters to them. 4) Impact of Covid-19. During the pandemic, greater efforts to maintain good communication were necessary. While negative impacts of Covid-19 were limited, caregivers appeared most disadvantaged by pandemic-related restrictions (e.g., limited visiting).

DISCUSSION

In glioblastoma treatment communication, building trusting relationships, maintaining a sense of control, and good support are identified by patients, caregivers, and HCPs as critical.

IDHwt Glioblastomas Show Opposing Resistance Mechanisms Across Patients in Response to Standard Treatment

AIMS

Glioblastoma (GBM) is the most common primary malignant brain tumour in adults. Despite aggressive treatment, a resistant tumour recurs in practically all patients. We therefore aimed to better understand the mechanisms driving this treatment resistance through investigating changes in gene expression across pairs of primary and recurrent GBM tumours.

METHOD

We generated or acquired bulk tumour RNA sequencing data for primary and first recurrent tumours from 107 patients who received standard treatment. Differential expression analysis between primary and recurrent samples found that the most dysregulated genes were involved in neurodevelopment and neurodifferentiation. We therefore used a publicly available ChIP-seq database to identify DNA binding factors for which binding sites are enriched in the promotors of genes with the largest expression changes from primary to recurrent.

RESULTS

Jumonji and AT-Rich Interacting Domain 2 (JARID2) was the most strongly enriched for binding to promotors of dysregulated genes. 65 patients showed an up-regulation and 42 showed a down-regulation of genes bound by this protein. The same set of JARID2 bound genes were found to be dysregulated in each direction, and correlated with the largest source of variation between samples in their response to treatment. Further enrichment analyses indicated that ‘Up’ responders may resist treatment through reduced proliferation and increased interaction with the tumour microenvironment, whereas ‘Down’ responders instead rely on a shift to mesenchymal cell states.

CONCLUSION

These results indicate that GBM tumours can be split into two subtypes that transcriptionally reprogramme in different directions through treatment and may benefit from different treatment approaches.

P11.64.A Long-term follow up and translational data from the ReoGlio phase Ib trial of GM-CSF and intravenous pelareorep (Reovirus) alongside standard of care in GBM

BACKGROUND

We previously reported safety data from a phase Ib, open-label study of intravenous oncolytic virus pelareorep with GM-CSF alongside standard chemoradiotherapy in newly diagnosed glioblastoma confirming that the combination is well tolerated. We now report on long-term follow up and analysis of translational samples from tumour and blood in a subset of patients.

METHODS

15 patients with newly diagnosed GBM were treated with GM-CSF 50μg subcutaneously on days 1-3 and intravenous pelareorep on days 4-5 in weeks 1 and 4 of chemoradiotherapy, and subsequently in week 1 of each adjuvant temozolomide course: 7 patients received 1x1010TCID50 (dose level 1); 8 received 3x1010TCID50 (dose level 2). The primary objective was to determine the maximum tolerated dose of pelareorep and GM-CSF with standard chemoradiotherapy. Following a protocol amendment we also collected survival data in all patients up to August 2021. Serial blood samples were taken from three patients, at baseline, during chemoradiotherapy and in the first adjuvant cycle. Peripheral blood mononuclear cells were analysed for immune checkpoint expression by flow cytometry, RNAseq gene expression and T-cell receptor clonality, whilst plasma cytokines were quantified by Luminex.

RESULTS

This combination was well tolerated with 87% of patients completing treatment as planned. Survival data analysis showed that median OS was 12.6 months in dose level 1 and 16.1 months in dose level 2, median OS for all patients was 13.1 months. The 24-month survival estimate for all patients was 25.0%, 16.7% for dose level 1 and 33.3% for dose level 2. One patient in dose level 1 remains alive at 43 months post registration without further treatment. Laboratory data showed that pelareorep infusion resulted in inflammatory cytokine and chemokine secretion, immune checkpoint modulation, and upregulation of inflammatory pathways. There was also increased peripheral clonal tumour-specific T-cell proliferation following pelareorep infusion.

CONCLUSION

Although based on small numbers, these long-term follow up data suggest this may be an active combination in a subset of GBM patients. Translational data confirm that pelareorep potentially activates tumour-targeting immune pathways in GBM, with consequential immune checkpoint modulation. These data support a combination clinical trial of pelareorep, radiotherapy and immune checkpoint blockade in GBM.

Cultural and linguistic disparities in dental utilisation in New South Wales, Australia

OBJECTIVE

To examine the patterns and predictors of dental utilisation in culturally and linguistically diverse (CALD) and non-CALD groups in New South Wales.

DESIGN

Secondary analysis of the 2013 and 2015 NSW Adult Population Health Survey (n=24,707).

MAIN OUTCOME

Dental utilisation, defined as a dental visit within the last 12 months. CALD groups were defined using country of birth and language. Andersen's theoretical model was used. Chi-square test and multivariate logistic regression analysis adjusted for potential confounding. Sample weights adjusted for sampling design.

RESULTS

Most (69%) of the population were Australian born; 20% spoke a language other than English at home. Dental utilisation was 58.9% and 63.9% for CALD and non-CALD groups respectively. The foreign-born non-English speaking group had the highest level of education (60%) but lower levels of dental utilisation (OR:0.81, CI 0.69-0.94) than all groups. Australian born non-English speakers had similar levels of dental utilisation to the reference group (OR:1.27, CI 0.99-1.63).

CONCLUSION

There are significant disparities in dental care utilisation among CALD populations. Foreign born, non-English speaking CALD migrants, and people experiencing socioeconomic disadvantage, are at greatest risk of inadequate dental utilisation. Furthermore, the combination of predisposing factors, language and cultural barriers compound disparities in oral health care utilisation. This data highlights the need for oral healthcare services that are sensitive to population needs, to reduce disparities among CALD communities residing in NSW.

Optimising tumour coverage and organ at risk sparing for hypofractionated re-irradiation in glioblastoma

BACKGROUND AND PURPOSE

Re-irradiation may be used for recurrent glioblastoma (GBM) patients. In some cases Planning Target Volume (PTV) under-coverage is necessary to meet organ at risk (OAR) constraints. This study aimed to develop a Volumetric Modulated Arc Therapy planning solution for GBM re-irradiation including a means of assessing if target coverage would be achievable and how much PTV 'cropping' would be required to meet OAR constraints, based on PTV volume and OAR proximity.

MATERIALS AND METHODS

For 10 PTVs, 360°, 180°, two coplanar 180° and 180° + non-coplanar 45° arc arrangements were compared using 35 Gy in 10 fractions. Using the preferred arrangement, dose fall-off was modelled to determine the separation required between PTV and OAR to ensure OAR dose constraints were met, with data presented graphically. To evaluate the graph as an aid to planning, seven cases with overlap were replanned in two treatment planning systems (TPSs).

RESULTS

There were no significant dosimetric differences between arc arrangements. 180° was preferred due to shorter treatment times. The graph, which indicated if 95% PTV coverage would be achievable based on PTV volume and OAR proximity, was employed in seven cases to guide planning in two TPSs. Plans were deliverable.

CONCLUSIONS

Re-irradiation treatment planning can be challenging, especially when PTV under-coverage is necessary. 180° was considered optimal. To assist in the planning process, graphical guidance was produced to inform planners whether PTV under-coverage would be necessary and how much PTV 'cropping' would be required to meet constraints during optimisation.

QOLP-14. LONG-TERM IMPACT OF ADULT GLIOMA ON HEALTH-RELATED QUALITY OF LIFE: A SYSTEMATIC REVIEW

BACKGROUND

Glioma diagnosis can be devastating, and results in a wide range of symptoms. Relatively little is known about the long-term challenges these symptoms pose on HRQOL. The aim of this review is to identify the long-term HRQOL issues reported at least two years following diagnosis of glioma.

METHOD

Systematic literature searches were carried out using Medline, EMBASE, CINAHL, PsycINFO, and Web of Science Core Collection. Searches were designed to identify a range of reported HRQOL aspects defined as physical, mental or social issues, in adult WHO grade II or III patients. To capture the full extent of patients’ experience, studies of any design reporting on primary data where patients had at least two years follow-up from diagnosis were included. WHO grade I and grade IV tumours were excluded due to their different prognoses and the expected nature of their disease trajectories. Narrative synthesis was used to collate findings.

RESULTS

The search returned 8438 articles. 477 titles remained after title and abstract screening, with seventeen full text articles included in the final analysis. The majority of studies used quantitative methods, with only two articles reporting qualitative or mixed methodology. Articles were predominantly cross-sectional studies (n = 9), along with cohort studies (n = 3), clinical trials (n = 3) and pilot studies (n = 2). Results indicated that patients reported a variety of issues influencing their HRQOL, with emotional/psychological/cognitive changes the most frequently reported. Physical complaints included problems with fatigue, seizures and maintaining daily activity. Social challenges included strained social relationships and issues managing finances. Patient coping strategies were found to significantly influence wellbeing and subsequent HRQOL.

CONCLUSION

Glioma patients’ long-term HRQOL and daily functioning can be impacted by their physical, mental and social wellbeing. Findings from this review lay the groundwork for efforts to improve patient long-term HRQOL.

P11.02 Long-term impact of primary brain tumour diagnosis on health-related quality of life: a systematic review

BACKGROUND

A primary brain tumour (PrBT) diagnosis can be devastating, and results in a wide range of symptoms. Relatively little is known about the long-term challenges these symptoms pose on HRQOL. The aim of this review is to identify the long-term HRQOL issues reported at least two years following diagnosis of a PrBT.

MATERIAL AND METHODS

Systematic literature searches were carried out using Medline, EMBASE, CINAHL, PsycINFO and Web of Science Core Collection. Searches were designed to identify a range of reported HRQOL aspects defined as physical, mental or social issues, in adult WHO grade II or III patients. To capture the full extent of patients’ experience, studies of any design reporting on primary data where patients had at least two years follow-up from diagnosis were included. WHO grade I and grade IV tumours were excluded due to their different prognoses and the expected nature of their disease trajectories. Quality assessment was conducted using the Mixed Methods Appraisal Tool (MMAT). Narrative synthesis was used to collate findings.

RESULTS

The search returned 8438 articles. 477 titles remained after title and abstract screening, with eighteen full text articles included in the final analysis. The majority of studies used quantitative methods, with only two articles reporting qualitative or mixed methodology. Articles were predominantly cross-sectional studies (n = 10), along with cohort studies (n = 3), clinical trials (n = 3) and pilot studies (n = 2). Results indicated that patients reported a variety of issues influencing their HRQOL, with emotional/psychological/cognitive changes being the most commonly reported. Physical complaints included problems with fatigue, seizures and maintaining daily activity. Social challenges included strained social relationships and issues managing finances. Patient coping strategies were found to significantly influence wellbeing and subsequent HRQOL.

CONCLUSION

PrBT patients’ long-term HRQOL and daily functioning can be impacted by their physical, mental and social wellbeing. Findings from this review lay the groundwork for efforts to improve patient HRQOL in long-term survivorship.

Glycolysis and Fatty Acid Oxidation Inhibition Improves Survival in Glioblastoma

Glioblastoma (GBM) is the most aggressive adult glioma with a median survival of 14 months. While standard treatments (safe maximal resection, radiation, and temozolomide chemotherapy) have increased the median survival in favorable O(6)-methylguanine-DNA methyltransferase (MGMT)-methylated GBM (~21 months), a large proportion of patients experience a highly debilitating and rapidly fatal disease. This study examined GBM cellular energetic pathways and blockade using repurposed drugs: the glycolytic inhibitor, namely dicholoroacetate (DCA), and the partial fatty acid oxidation (FAO) inhibitor, namely ranolazine (Rano). Gene expression data show that GBM subtypes have similar glucose and FAO pathways, and GBM tumors have significant upregulation of enzymes in both pathways, compared to normal brain tissue (p < 0.01). DCA and the DCA/Rano combination showed reduced colony-forming activity of GBM and increased oxidative stress, DNA damage, autophagy, and apoptosis in vitro. In the orthotopic Gl261 and CT2A syngeneic murine models of GBM, DCA, Rano, and DCA/Rano increased median survival and induced focal tumor necrosis and hemorrhage. In conclusion, dual targeting of glycolytic and FAO metabolic pathways provides a viable treatment that warrants further investigation concurrently or as an adjuvant to standard chemoradiation for GBM.

CTIM-14. PELAREOREP AND GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR (GM-CSF) WITH STANDARD CHEMORADIOTHERAPY/ADJUVANT TEMOZOLOMIDE FOR GLIOBLASTOMA MULTIFORME (GBM) PATIENTS: REOGLIO PHASE I TRIAL RESULTS

BACKGROUND

Oncolytic viruses represent a novel treatment approach in GBM through oncolytic targeting as well as local immune activation. We designed a phase Ib, open-label study of intravenous reovirus (pelareorep) with GM-CSF alongside standard chemoradiotherapy to assess safety and tolerability.

METHODS

15 patients with newly diagnosed GBM were treated with GM-CSF 50mg subcutaneously (days 1–3) and pelareorep (days 4–5) in weeks 1 and 4 of chemoradiotherapy, and week 1 of adjuvant temozolomide course: 7 patients received 1x1010TCID50 (dose level 1); 8 received 3x1010TCID50 (dose level 2). The primary objective was to determine the maximum tolerated dose of pelareorep and GM-CSF with standard chemoradiotherapy. Secondary objectives were to gain preliminary assessment of the activity of the combination and assess treatment compliance.

RESULTS

1 dose limiting toxicity (DLT) and 20 SAEs were experienced overall; median number of SAEs per patient was 2. Commonest SAEs were nervous system disorders, predominantly seizures. SARs included fever/flu-like episodes (n=5), fall (n=1) and headache (n=1). Two SUSARs occurred in dose level 2, classed as vascular disorders manifesting as hypotension episodes – one was a DLT. Suspected relationship of SARs: pelareorep (n=6); temozolomide (n=1); radiotherapy (n=1); all study drugs (n=1). 87% of patients (n=13) completed chemoradiotherapy without unplanned delays. Adjuvant treatment was delayed in 21% of cycles overall, with the majority due to inadequate haematology/biochemistry values (44% of delays). Pelareorep was omitted in 4 instances in 4 patients during chemoradiotherapy and omitted in 4 instances in 3 patients during adjuvant treatment.

CONCLUSION

We present the first clinical data using intravenous pelareorep with GM-CSF alongside standard chemoradiotherapy in patients with GBM, suggesting that the combination is tolerable. Further analysis is underway and efficacy results will be ready for presentation at the conference. This work was supported by CRUK, The Brain Tumour Charity, Yorkshire Cancer Research and Oncolytics Biotech Inc.

Gender issues from the perspective of health-care professionals in Neuro-oncology: an EANO and EORTC Brain Tumor Group survey

Background

Women represent an increasing proportion of the overall workforce in medicine but are underrepresented in leadership roles.

Methods

To explore gender inequalities and challenges in career opportunities, a web-based survey was conducted among the membership of the European Association of Neuro-Oncology and the Brain Tumor Group of the European Organisation for Research and Treatment of Cancer.

Results

A total of 228 colleagues responded to the survey: 129 women (median age 45 years; range, 25-66 years) and 99 men (median age 48 years; range, 24-81 years); 153 participants (67%) were married and 157 participants (69%) had at least 1 child. Women less often declared being married (60% vs 77%, P = .007) or having a child (63% vs 77%, P = .024). Men more frequently had a full-time position (88% vs 75%, P = .036). Women and men both perceived an underrepresentation of women in leadership positions. Half of participants agreed that the most important challenges for women are leading a team and obtaining a faculty position. Fewer women than men would accept such a position (42% vs 56%). The main reasons were limited time for career and an inappropriate work and life balance. Women specifically cited negative discrimination, limited opportunities, and lack of self-confidence. Discrimination of women at work was perceived by 64% of women vs 47% of men (P = .003).

Conclusion

Women are perceived as experiencing more difficulties in acquiring a leadership position. Personal preferences may account for an underrepresentation of women in leadership positions, but perceived gender inequalities extend beyond disparities of access to leadership.

The impact of the neuro-oncology research radiographer role in the effective facilitation of an advanced imaging study in glioblastoma

Background

A neuro-oncology research radiographer was included in the multi-disciplinary study team (MDT) from the set-up stage of a new advanced imaging study in glioblastoma, as it was envisaged that this would enhance progress and provide better patient-centred care.

Aims

This pilot study aimed to include 12 participants. This specialist radiographer role was to support recruitment, co-ordinate appointments and monitor patients’ progress. We aimed to ensure that optimal treatment and patient-centred care remained at the forefront of the study pathway.

Method

Patients were identified and approached by the radiographer prior to consent by a trial investigator. Additional scans were planned prior to radiotherapy (RT), 2 weeks into RT and 6 weeks post RT. The radiographer ensured streamlined appointments and was present during each study visit to liaise with health professionals, provide a specific point of contact with the patient and to ensure continuity.

Results

6 patients have been recruited since November 2018. The specialist radiographer has attended 28 study scans to date. Over 40 face-to-face interactions have been undertaken, 30 email communications and 18 telephone consultations. Patient feedback has been extremely positive, all patients convey that they feel supported and value continuity throughout the pathway. Enhanced communication across the entire study team has also guaranteed efficient recruitment.

Conclusion

The research radiographer has a key role in the multi-disciplinary team delivering this study. Effective liaison between the radiotherapy and imaging departments has been crucial and patients value a consistent point of contact through the study and treatment pathways.

Chromatin remodelling to facilitate treatment resistance in glioblastoma

Recent findings from our group, and the wider community, show that standard treatment does not impose an apparent bottleneck on the clonal evolution of adult glioblastoma (GBM), implying a lack of direct therapeutic opportunity. This does not negate the possibility that multiple treatment-resistance mechanisms co-exist in tumours, repeated across patients, making a combination of targeted therapies a potentially effective approach. We investigated whether treatment resistance may be driven by selection of cellular properties conferred above the level of the genome. Differential expression analysis was performed on 23 pairs of primary and recurrent tumours from patients who received standard treatment and had a local recurrence treated by surgery and second line chemotherapy. This revealed a treatment-induced shift in cell states linked to normal neurodevelopment. The latter is orchestrated by cascades of transcription factors. We, therefore, applied a bespoke gene set enrichment analysis to our paired expression data to investigate whether any factors were implicated in co-regulation of the genes that were altered through therapy. This identified a specific chromatin remodelling machinery, instrumental in normal neurogenesis. We validated our results in an independent cohort of 22 paired GBM samples. Our results suggest that the chromatin remodelling machinery is responsible for determining transcriptional hierarchies in GBM, shown elsewhere to have different treatment sensitivities such that their relative abundances are altered through treatment.

OS9.5 Evidence that adult glioblastoma adapts to standard therapy though chromatin remodeling

BACKGROUND

Glioblastoma (GBM) tumours recur following standard treatment in almost all cases. We use ‘omics technologies to simultaneously profile pairs of primary and matched recurrent GBM to specifically identify and characterise the cells that resisted treatment, with the aim of determining how to more effectively kill them.

MATERIAL AND METHODS

We have analysed high coverage RNAseq data from pairs of GBM tumours: primary de novo tumour and matched local recurrence from patients that underwent standard therapy. Our original cohort constituted 23 pairs and our validation cohort was an additional 22 pairs. We also cultured two plates of spheroids directly from a patient’s GBM, treating one with radiation and temozolomide. We monitored growth and captured and sequenced RNA from single cells at two time-points: one week post-treatment when the deviation between untreated and treated spheroid growth curves was most pronounced; and three weeks post-treatment when the growth rate of treated spheroids had recovered. We investigated differential gene expression between primary and recurrent pairs, and single cells pre- and post-treatment, and performed a bespoke per patient gene set enrichment analysis.

RESULTS

Differential gene expression analysis in 23 tumour pairs indicated a treatment-induced shift in cell states linked to normal neurogenesis and prompted us to develop a novel gene set enrichment analysis approach to identify gene regulatory factors that may orchestrate such a shift. This revealed the significant and universal dysregulation of genes, through therapy, that are targeted by a specific chromatin remodeling machinery. This finding was validated in an independent cohort of 22 further GBM pairs. To understand the therapeutic potential of this finding we must determine whether genes are dysregulated through therapy owing to a) their fixed expression in inherently treatment resistance cells in the primary tumour which get selected during therapy to increase the signal of that profile, or b) changes in expression during the process of cells acquiring treatment resistance. To inspect this, we analysed single cell gene expression data from GBM spheroids pre- and post-treatment. We found that there was significant dysregulation of the genes associated with the chromatin remodeling complex but only at the three-week post-treatment time-point.

CONCLUSION

Our results indicate that GBM cells are being transcriptionally reprogrammed in response to treatment; the mechanism of which may represent a therapeutic opportunity.

PL3.6 Targeting GSK-3 activity promotes mitotic catastrophe via centrosome destabilisation and enhances the effect of radiotherapy in glioma models

BACKGROUND

Targeting kinases as regulators of cellular processes that drive cancer progression is a promising approach to improve patient outcome in GBM management. The glycogen synthase kinase 3 (GSK-3) plays a role in cancer progression and is known for its pro-proliferative activity in gliomas. The anti-proliferative and cytotoxic effects of the GSK-3 inhibitor AZD2858 were assessed in relevant in vitro and in vivo glioma models to confirm GSK-3 as a suitable target for improved single agent or combination treatments.

MATERIAL AND METHODS

The immortalised cell line U251 and the patient derived cell lines GBM1 and GBM4 were used in in vitro studies including MTT, clonogenic survival, live cell imaging, immunofluorescence microscopy and flow cytometry to assess the cytotoxic and anti-proliferative effects of AZD2858. Observed anti-proliferative effects were investigated by microarray technology for the identification of target genes with known roles in cell proliferation. Clinical relevance of targeting GSK-3 with the inhibitor either for single agent or combination treatment strategies was determined by subcutaneous and orthotopic in vivo modelling. Whole mount mass spectroscopy was used to confirm drug penetration in orthotopic tumour models.

RESULTS

AZD2858 was cytotoxic at low micromolar concentrations and at sub-micromolar concentrations (0.01 - 1.0 μM) induced mitotic defects in all cell lines examined. Prolonged mitosis, centrosome disruption/duplication and cytokinetic failure leading to cell death featured prominently among the cell lines concomitant with an observed S-phase arrest. No cytotoxic or anti-proliferative effect was observed in normal human astrocytes. Analysis of the RNA microarray screen of AZD2858 treated glioma cells revealed the dysregulation of mitosis-associated genes including ASPM and PRC1, encoding proteins with known roles in cytokinesis. The anti-proliferative and cytotoxic effect of AZD2858 was also confirmed in both subcutaneous and orthotopic in vivo models. In addition, combination treatment with AZD2858 enhanced clinically relevant radiation doses leading to reduced tumour volume and improved survival in orthotopic in vivo models.

CONCLUSION

GSK-3 inhibition with the small molecule inhibitor AZD2858 led to cell death in glioma stem cells preventing normal centrosome function and promoting mitotic failure. Normal human astrocytes were not affected by treatment with the inhibitor at submicromolar concentrations. Drug penetration was observed alongside an enhanced effect of clinical radiotherapy doses in vivo. The reported aberrant centrosomal duplication may be a direct consequence of failed cytokinesis suggesting a role of GSK-3 in regulation of mitosis in glioma. GSK-3 is a promising target for combination treatment with radiation in GBM management and plays a role in mitosis-associated events in glioma biology.

P11.13 Radiotherapy combined with a multimodal imaging approach in a glioblastoma preclinical model

BACKGROUND

Glioblastoma multiforme (GBM) carries a poor prognosis, partly due to biological and anatomical heterogeneity. Although radiotherapy (RT) is effective, high doses damage surrounding healthy tissues. Multimodal imaging with Magnetic Resonance (MRI) and Positron Emission Tomography (PET) may represent a useful approach for identifying GBM heterogeneity and visualising metabolic tumour properties. PET radiotracer [18F]-fluciclovine is preferentially accumulated in gliomas compared to healthy brain tissue via the cellular transport systems, LAT1 and ASCT2. In this study the effect of fractionated RT using multimodal imaging including [18F]-fluciclovine uptake and immunohistochemistry (IHC) in a GBM preclinical model will be validated.

MATERIAL AND METHODS

Two C57BL/6J mice cohorts were injected intracranially (i.c.) with murine CT2A-luc cells and subsequently submitted to multiparametric MRI and [18F]-fluciclovine PET imaging during hemi-brain RT (3Gy on 2 days/each week) for maximum 25 days after i.c. injection. Brains were collected for IHC characterization including LAT1 and ASCT2 staining.

RESULTS

Preliminary data showed that both MRI and PET were effective modalities to track tumour growth in this model. PET data revealed up to greater than 3-fold increase in SUVmax from regions of interest around the tumour site compared to healthy brain tissue. Time activity curves showed a steady increase in tumour uptake over 90 minutes. MRI showed a 25% increase in T2 values in tumours relative to unaffected contralateral regions. Confirmation of treatment response through matched imaging and IHC are ongoing, from which changes in glioma cell biology as well as amino acid transporter protein levels will be analysed.

CONCLUSION

These preliminary results show that multimodal imaging presents novel data in the assessment of treatment response in this model and will permit parallel IHC analyses to better define GBM tumour heterogeneity aligned with imaging changes. These data will also inform an on-going clinical study using the same imaging modalities.

Work at authors’ labs are supported by an Investigator initiated project from Blue Earth Diagnostics (AS, SCS) and a University of Leeds Biswas studentship (SCS, DS). Daniela Salvatore is also supported by a Scholarship provided by Molecular and Translational Medicine Doctorate School of University of Milan (Italy).

Abstract 5215: Targeting of HOX-PBX binding in glioblastoma multiforme as a novel therapeutic treatment

The HOX genes encode a family of transcription factors that play an essential role in embryonic patterning. They are also aberrantly expressed in numerous cancers, including glioblastoma (GBM). Three Amino Acid Loop Extension Homeobox (TALE) proteins act as important co-factors for HOX proteins, modulating their binding affinities to genomic targets. TALE proteins include the Pre-B-cell leukemia homeobox (PBX) proteins 1-4, which bind anterior HOX proteins, facilitating their nuclear entry and limiting their degradation. HTL00-1 is a 2nd generation hexapeptide drug that inhibits HOX-PBX dimer formation, and has been shown to induce rapid apoptosis in cancer cells, but not normal cells, through the rapid upregulation of genes including cFos, DUSP1, and EGR1. We have found that both HOX and TALE genes are markedly dysregulated in primary GBM tumors as well as in murine (GL261), adult (LN18, U87-MG, U251-MG) and pediatric (KNS42, SF188) GBM cell lines, all of which are sensitive to HTL-001. These genes were even more highly expressed in experimentally induced GBM cancer stem cells (CSCs) compared with parental lines, with a corresponding increase in sensitivity to HTL-001. We also investigated the in vivo activity of HTL-001 in Black 6 mice carrying GL-261 subcutaneous and orthotropic tumors with twice weekly intraperitoneal delivery. HTL-001 was shown to cross the blood brain barrier using Alexa660 labelled peptide, and significant anti-tumor activity was observed in both subcutaneous and orthotropic models with increased survival (p&lt;0.02 and p&lt;0.0078, respectively). Resected tumors from HTL-001 treated mice showed marked evidence of apoptosis, tumor vasculature disruption and focal necrosis compared to untreated tumors. Taken together, our findings indicate that HOX-PBX inhibition is a potential therapeutic target for adult and pediatric GBM patients.

Citation Format: Richard Morgan, Monika Primon, Steven Shnyder, Susan Short, Balveen Kaur, Bangxing Hong, Izhar Bagwan, William Rogers, Hardev S. Pandha. Targeting of HOX-PBX binding in glioblastoma multiforme as a novel therapeutic treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5215.

Senolytics and senostatics as adjuvant tumour therapy

Cell senescence is a driver of ageing, frailty, age-associated disease and functional decline. In oncology, tumour cell senescence may contribute to the effect of adjuvant therapies, as it blocks tumour growth. However, this is frequently incomplete, and tumour cells that recover from senescence may gain a more stem-like state with increased proliferative potential. This might be exaggerated by the induction of senescence in the surrounding niche cells. Finally, senescence will spread through bystander effects, possibly overwhelming the capacity of the immune system to ablate senescent cells. This induces a persistent system-wide senescent cell accumulation, which we hypothesize is the cause for the premature frailty, multi-morbidity and increased mortality in cancer survivors. Senolytics, drugs that selectively kill senescent cells, have been developed recently and have been proposed as second-line adjuvant tumour therapy. Similarly, by blocking accelerated senescence following therapy, senolytics might prevent and potentially even revert premature frailty in cancer survivors. Adjuvant senostatic interventions, which suppress senescence-associated bystander signalling, might also have therapeutic potential. This becomes pertinent because treatments that are senostatic in vitro (e.g. dietary restriction mimetics) persistently reduce numbers of senescent cells in vivo, i.e. act as net senolytics in immunocompetent hosts.