GFAP splice variants fine-tune glioma cell invasion and tumour dynamics by modulating migration persistence

Glioma is the most common form of malignant primary brain tumours in adults. Their highly invasive nature makes the disease incurable to date, emphasizing the importance of better understanding the mechanisms driving glioma invasion. Glial fibrillary acidic protein (GFAP) is an intermediate filament protein that is characteristic for astrocyte- and neural stem cell-derived gliomas. Glioma malignancy is associated with changes in GFAP alternative splicing, as the canonical isoform GFAPα is downregulated in higher-grade tumours, leading to increased dominance of the GFAPδ isoform in the network. In this study, we used intravital imaging and an ex vivo brain slice invasion model. We show that the GFAPδ and GFAPα isoforms differentially regulate the tumour dynamics of glioma cells. Depletion of either isoform increases the migratory capacity of glioma cells. Remarkably, GFAPδ-depleted cells migrate randomly through the brain tissue, whereas GFAPα-depleted cells show a directionally persistent invasion into the brain parenchyma. This study shows that distinct compositions of the GFAPnetwork lead to specific migratory dynamics and behaviours of gliomas.

A pilot study of machine-learning based automated planning for primary brain tumours

Purpose High-quality radiotherapy (RT) planning for children and young adults with primary brain tumours is essential to minimize the risk of late treatment effects. The feasibility of using automated machine-learning (ML) to aid RT planning in this population has not previously been studied. Methods and materials We developed a ML model that identifies learned relationships between image features and expected dose in a training set of 95 patients with a primary brain tumour treated with focal radiotherapy to a dose of 54 Gy in 30 fractions. This ML method was then used to create predicted dose distributions for 15 previously-treated brain tumour patients across two institutions, as a testing set. Dosimetry to target volumes and organs-at-risk (OARs) were compared between the clinically-delivered (human-generated) plans versus the ML plans. Results The ML method was able to create deliverable plans in all 15 patients in the testing set. All ML plans were generated within 30 min of initiating planning. Planning target volume coverage with 95% of the prescription dose was attained in all plans. OAR doses were similar across most structures evaluated; mean doses to brain and left temporal lobe were lower in ML plans than manual plans (mean difference to left temporal, – 2.3 Gy, p = 0.006; mean differences to brain, – 1.3 Gy, p = 0.017), whereas mean doses to right cochlea and lenses were higher in ML plans (+ 1.6–2.2 Gy, p < 0.05 for each). Conclusions Use of an automated ML method to aid RT planning for children and young adults with primary brain tumours is dosimetrically feasible and can be successfully used to create high-quality 54 Gy RT plans. Further evaluation after clinical implementation is planned.

Assessment of Structural Disconnections In Gliomas: Comparison of Indirect And Direct Approaches

Gliomas are amongst the most common primary brain tumours in adults and are often associated with poor prognosis. Understanding the extent of white matter (WM) which is affected outside the tumoral lesion may be of paramount importance to explain cognitive deficits and the clinical progression of the disease. To this end, we explored both direct (i.e., tractography based) and indirect (i.e., atlas based) approaches to quantifying WM structural disconnections in a cohort of 50 high- and low-grade glioma patients. While these methodologies have recently gained popularity in the context of stroke, to our knowledge this is the first time they are applied in patients with brain tumours. More specifically, in this work we present a quantitative comparison of the disconnection maps provided by the two methodologies by applying well known metrics of spatial similarity, extension and correlation. Given the important role the oedematous tissue plays in the physiopathology of tumours, we performed these analyses both by including and excluding it in the definition of the tumoral lesion. This was done to investigate possible differences determined by this choice.We found that direct and indirect approaches offer two distinct pictures of structural disconnections in patients affected by brain gliomas, presenting key differences in several regions of the brain. Following the outcomes of our analysis, we eventually discuss the strengths and pitfalls of these two approaches when applied in this critical field.

STEM-02. THERAPEUTIC INTERVENTION OF LUNG-, BREAST-, AND MELANOMA-BRAIN METASTASIS

BACKGROUND The incidence of brain metastases (BM) is tenfold higher than that of primary brain tumours. BM predominantly originate from primary lung, breast, and melanoma tumours with a 90% mortality rate within one year of diagnosis, posing a large unmet clinical need to identify novel therapies against BM.This unmet clinical need is largely attributed to a small population of cancer stem cells (CSCs), termed BM-initiating cells (BMICs), that are able to escape a primary tumour, drive metastasis and facilitate the formation of a secondary tumour in the brain. METHODS Using a large in-house biobank of patient-derived BMIC lines, the Singh Lab has generated murine orthotopic patient-derived xenograft models of BM and captured a “premetastatic” population of BMICs that have just seeded the brains of mice before forming clinically detectable tumours: a cell population that is impossible to detect in human patients but represents a therapeutic window wherein metastasizing cells can be targeted and eradicated before establishing clinically detectable tumours. RESULTS RNA sequencing of pre-metastatic BMICs from all three primary tumour models with subsequent Connectivity Map analysis identified a lead compound that exhibits selective anti-BM activity in vitro. Preliminary in vivo work has shown that this lead compound reduces the tumor burden of treated mice compared to vehicle control while providing a significant survival advantage. Ongoing mechanistic investigations aim to delineate the protein target of this compound in the context of the observed selective anti-BMIC phenotype. CONCLUSION Identification of novel small molecules that target premetastatic BM cells could prevent the formation of BM and dramatically improve the prognosis of at-risk cancer patients.

Developing guidelines for the management of brain tumour related epilepsy

Aims Brain Tumour Related Epilepsy (BTRE) has a significant impact on Quality of Life with implications for driving, employment and social and domestic activities. Management of BTRE is complex due to the higher incidence of pharmacoresistance and the potential for interaction between anti-cancer therapy and anti-epileptic drugs (AEDs). Neurologists, oncologists, palliative care physicians and clinical nurse specialists treating these patients would benefit from up-to-date clinical guidelines. We aim to review the current evidence to adapt current NICE guidelines for Epilepsy and to outline specific recommendations for the optimal treatment of BTRE, encompassing both primary and metastatic brain tumours. Method A comprehensive search of the literature from the past 20 years on BTRE was carried out in three databases: Embase, Medline and EMCARE. A broad search strategy was used and the evidence was evaluated and graded based on the Oxford Centre for Evidence-Based Medicine Levels of Evidence. Results All patients with BTRE should be treated with AEDs. There is no proven benefit for the use of prophylactic AEDs, although there are no randomised trials testing newer agents. Seizure frequency varies between 10-40% (Class 2a evidence) in patients with Brain Metastases (BM) and from 30% (high-grade gliomas) to 90% (low-grade gliomas) (Class 2a evidence) in patients with Primary Brain Tumours (PBT). In patients with BM, risk factors include number of BM and melanoma histology (Class 2b evidence). In patients with PBT, risk factors include frontal and temporal location, oligodendroglial histology, IDH mutation and cortical infiltration (Class 2b evidence). There is a low incidence of seizures (13%) after stereotactic radiosurgery for BM (Class 2b evidence). Non-enzyme inducing AEDs are recommended as first line treatment for BTRE, but up to 50% of patients with BTRE due to PBT remain resistant (Class 2b evidence). Conclusion The review has highlighted the relative dearth of high quality evidence for the management of BTRE, and provides a framework for further studies aiming to improve seizure control, quality of life, and indications for AEDs.

Temozolomide hypersensitivity – A story of success

Aims Background: Temozolomide is an oral chemotherapy drug widely used in the treatment of glial tumours. This is generally well tolerated however, immediate and delayed hypersensitivity reactions have been described, necessitating treatment interruption that could significantly impact survival. Method Case description: We report a case of a 39-year-old young woman with WHO grade 2 IDH1mutant diffuse astrocytoma (MGMT promoter methylated) of the left temporal lobe. She had tumour resection in 2012 followed by radical radiotherapy. Afterwards, she had close surveillance with regular brain imaging. The tumour started to progress in early 2020. We agreed to commence on temozolomide to control tumour growth. She developed an itchy rash with easy bruising towards the end of the first cycle. It responded to a course of prednisolone. We proceeded with the second cycle and she developed a worsening rash on the third day. However she did not have signs or symptoms of anaphylaxis. This episode was again managed by a course of steroids and oral antibiotics. Since Temozolomide was the optimal treatment to control the disease progression at this stage, we agreed to persevere with temozolomide using a rapid desensitisation protocol. Results On the first day of third cycle, she was brought to the day chemotherapy unit and given prednisolone 30mg, fexofenadine 180mg and ondansetron 8mg, 30 minutes before the treatment. Our protocol was as follows; 5mg, 10mg, 20mg, 30mg, 50mg and 90mg of temozolomide at an interval of 30 minutes between the doses. She was advised to follow the same regime for the next four days of the third cycle. On days 6 -28, she has been advised to take fexofenadine 180mg once daily. Although there was a minor rash appeared on days 6/7, they subsided gradually. She tolerated the treatment without sinister symptoms or signs. We proceeded with the next 4 chemotherapy cycles adhering to the same protocol. The intensity of the rash gradually improved, and she became almost completely asymptomatic by the 7th cycle. It was also encouraging to see the radiological response of the tumour with the treatment. Conclusion Although the published literature is minimal, rapid desensitisation is shown to be a safe and effective method to counteract temozolomide hypersensitivity. In an era where there is still a paucity of systemic treatment options for primary brain tumours, adopting rapid desensitisation to induce tolerability to temozolomide, a drug which has shown to improve survival, would be a valuable addition in managing our patients. Further, our experience suggests that this protocol is safe, effective, and does not necessitate inpatient admission.

Readmission and reoperation rates after resection of malignant primary brain tumours in England 2013-2017

Aims Morbidity and mortality following resection of malignant primary brain tumours is high. The benefits of reoperation for recurrent tumours are uncertain and it is not known how frequently patients in England undergo further tumour resections. The aim of this study was to describe 30-day and one-year readmission rates, the clinical reasons for readmission and the rate of resections for recurrent tumours. Method Patient data was extracted from Hospital Episode Statistics (the hospital administrative data for NHS hospitals in England) for all supratentorial, malignant, primary brain tumour resections performed from April 2013 to March 2017. All subsequent non-elective readmissions to any NHS hospital and all readmissions for further tumour resection within 30 days and one year were analysed for the primary clinical diagnosis and primary procedure performed. Results A total of 6,982 patients were identified and the 30-day and one-year readmission rates were 18.6% (n=1,298) and 57.4% (n=4,007), respectively. The rates of reoperation for tumour resection were 0.5% (n=33) and 6.2% (n=432), respectively. The commonest reasons for 30-day readmission were post-operative complications (17.9% of admissions), general medical complications (17.3%) and surgical site infection (9.6%). The most frequently performed neurosurgical procedures were for treatment of surgical site infection (37.6% of procedures). The commonest reasons for readmission within one year were general medical complications (17.4%), seizures (14%), systemic infections (11.4%) and post-operative complications (11%). Almost half of all neurosurgical procedures performed within one year were reoperation for tumour resection (45.6%), while treatment of surgical site infection (17.9%) and CSF shunt insertions and revisions (9.1%) were also common. Conclusion This study provides a descriptive analysis of the rates of readmission, diagnosis on readmission, and the need for further neurosurgical procedures. The rate of non-elective readmissions within one year is high and these data may be useful for service planning and for counselling patients about their treatment. Additionally, these data contribute to the development of quality indicators, for benchmarking and comparing quality of care provision between neurosurgical units. Further research, with linkage to histology data and performance status, would support an analysis of the role of resection of recurrent, malignant, primary brain tumours.