CDKN2A/B Homozygous Deletions in Astrocytomas: A Literature Review

Genomic alterations of CDKN2A and CDKN2B in astrocytomas have been an evolving area of study for decades. Most recently, there has been considerable interest in the effect of CDKN2A and/or CDKN2B (CDKN2A/B) homozygous deletions (HD) on the prognosis of isocitrate dehydrogenase (IDH)-mutant astrocytomas. This is highlighted by the adoption of CDKN2A/B HD as an essential criterion for astrocytoma and IDH-mutant central nervous system (CNS) WHO grade 4 in the fifth edition of the World Health Organisation (WHO) Classification of Central Nervous System Tumours (2021). The CDKN2A and CDKN2B genes are located on the short arm of chromosome 9. CDKN2A encodes for two proteins, p14 and p16, and CDKN2B encodes for p15. These proteins regulate cell growth and angiogenesis. Interpreting the impact of CDKN2A/B alterations on astrocytoma prognosis is complicated by recent changes in tumour classification and a lack of uniform standards for testing CDKN2A/B. While the prognostic impact of CDKN2A/B HD is established, the role of different CDKN2A/B alterations-heterozygous deletions (HeD), point mutations, and promoter methylation-is less clear. Consequently, how these alternations should be incorporated into patient management remains controversial. To this end, we reviewed the literature on different CDKN2A/B alterations in IDH-mutant astrocytomas and their impact on diagnosis and management. We also provided a historical review of the changing impact of CDKN2A/B alterations as glioma classification has evolved over time. Through this historical context, we demonstrate that CDKN2A/B HD is an important negative prognostic marker in IDH-mutant astrocytomas; however, the historical data is challenging to interpret given changes in tumour classification over time, variation in the quality of evidence, and variations in the techniques used to identify CDKN2A/B deletions. Therefore, future prospective studies using uniform classification and detection techniques are required to improve the clinical interpretation of this molecular marker.

Increased rates of cetuximab reactions in tick prevalent regions and a proposed protocol for risk mitigation

BACKGROUND

Cetuximab is an anti-epidermal growth factor receptor mouse-human chimeric monoclonal antibody used to treat advanced colorectal cancers. Initial data suggest that severe infusion reactions occurred in 4.5%, many on first exposure. The majority of those with anaphylactic reactions possess predeveloped IgE antibodies to galactose-alpha-1,3-galactose. It is thought that the vector for preexposure to alpha-gal is antigen inoculation via tick bites. This retrospective study reviews the experience of two community cancer centers in high tick exposure areas in Sydney with cetuximab anaphylaxis and proposes a protocol to avoid this.

METHOD

Severe cetuximab infusion reactions occurring in the Northern Cancer Institute Frenchs Forest and St Leonards clinics, Sydney, from May 2014 to February 2019 were recorded. Area of residence was then compared to areas of known high tick prevalence.

RESULTS

A total of 87 patients received cetuximab in this period. Six patients (6.9%) experienced at least a grade 3 reaction, three females, age range 41-72 years (median 57.5 years). All were receiving cetuximab for metastatic colorectal cancer and their anaphylaxis occurred with the first infusion in all cases.

CONCLUSION

These cases support the existing theory of increased rates of cetuximab anaphylaxis in areas of high tick prevalence. Given this, we recommend the following protocol for patients being considered for cetuximab therapy: known mammalian meat allergy as an absolute contraindication; all patients receiving cetuximab should have RAST (ImmunoCAP^® ) testing for alpha-gal specific-IgE-specific antibodies before first infusion and those who test positive to be considered alternate therapy.

Implications of Concurrent IDH1 and IDH2 Mutations on Survival in Glioma-A Case Report and Systematic Review

Both IDH1 (isocitrate dehydrogenase 1) and IDH2 (isocitrate dehydrogenase 2) mutations play a vital role in the development of gliomas through disruption of normal cellular metabolic processes. Here we describe a case of a patient with an IDH-mutant astrocytoma, in which both IDH1 and IDH2 mutations were detected within the same tumour. The patient remains disease-free, nine and a half years after her initial diagnosis. Interrogation of cancer genomic databases and a systematic review was undertaken, demonstrating the rarity of the co-occurrence of IDH1 and IDH2 mutations in a variety of cancer types, and in glioma specifically. Due to the favourable outcome observed in this patient, the potential effect of concurrent IDH1 and IDH2 mutations on survival was also investigated.

Hypercalcaemia secondary to hypophysitis and cortisol deficiency: another immunotherapy-related adverse event

Summary

Hypercalcaemia is a common complication seen in malignancy, frequently due to paraneoplastic parathyroid hormone-related peptide production or osteolytic bony metastases. We present a 58-year-old female with immunotherapy-mediated hypophysitis causing secondary cortisol deficiency resulting in severe glucocorticoid-responsive hypercalcaemia. Whilst hypophysitis is a well recognised adverse event in those receiving immunotherapy for advanced malignancy, it does not typically present with hypercalcaemia. The mechanism responsible for hypercalcaemia due to hypocortisolaemia has not been fully elucidated although hypotheses include the effects of volume depletion and thyroxine's action on bone. Prompt treatment with glucocorticoids caused an improvement in the patient's symptoms and corrected her hypercalcaemia which later returned after an attempted glucocorticoid wean. With the increasing uptake of immunotherapy, clinicians should be aware of this unusual presentation of immunotherapy-related hypophysitis and secondary hypocortisolaemia which can be life-threatening if the diagnosis is delayed.

Learning points

Immunotherapy can cause inflammation of the pituitary gland resulting in secondary hypocortisolaemia, which can, though rarely, present as hypercalcaemia. Secondary hypocortisolaemia requires prompt recognition and treatment with glucocorticoids. Glucocorticoid replacement leads to rapid clinical and biochemical improvement in these patients. The differential diagnosis for glucocorticoid-responsive hypercalcaemia extends beyond granulomatous disorders (e.g. sarcoidosis, tuberculosis) to adrenocorticotrophic hormone and cortisol deficiency, particularly in patients receiving immunotherapy. Hypocortisolaemia can lead to hypercalcaemia through various proposed mechanisms. Low serum glucocorticoids are associated with reduced blood volume, thus reducing renal calcium excretion. In addition, without glucocorticoid's inhibitory action, thyroxine appears to drive calcium mobilisation from bone.

PATH-18. A MULTI-CENTER CASE SERIES OF ADULT K27M MUTATED DIFFUSE MIDLINE GLIOMAS REVEALING A POPULATION UNIQUE FROM PAEDIATRIC CASES

BACKGROUND

Histone mutations in the K27M gene were first described in 2014, and incorporated into the WHO CNS tumour classification system in 2016. They are typically associated with diffuse midline gliomas (DMG). Presenting symptoms vary greatly, with some experiencing significant delay in diagnosis. Median survival is only 9-12 months for these patients. Biopsy samples are small, and in some due to location, not performed. Although data is predominately based on the paediatric population, DMGs are seen in both adolescence and adults. In this multi-site retrospective study, we describe 11 adult patients with K27M DMG gliomas across two tertiary Neuro-Oncology services in Sydney, Australia. To the authors’ knowledge we present the largest known collection of adult K27M cases in the Asia-Pacific region with correlation of treatment, clinicopathologic and radiologic features with outcomes.

METHODS

The glioma databases of Royal North Shore Hospital (RNSH) and Royal Prince Alfred Hospital (RPAH) between January 2009 and March 2020 were interrogated to identify patients. Selection criteria included patients aged ≥ 18 years who presented with a DMG, had undergone biopsy, and had confirmed K27M via next generation sequencing. Clinicopathologic, radiologic and treatment outcomes were extracted for correlation.

RESULTS

Eleven patients fitting the selection criteria were identified and reported. The median age at diagnosis was 30 years and 4 were female. Five presented with hydrocephalus, the most common presenting symptoms were headaches and nausea and/or vomiting (n= 4 and n= 2 respectively). The median progression-free survival was 13 months (4-31 months) and the median overall survival was 23 months (4-59 months).

CONCLUSION

This case series reports the outcomes of older patients with K27M. The clinical course demonstrated suggests a divergence from paediatric biology. Ongoing studies are required to further characterise the histopathological and clinical differences of these tumours in older patients.

Anti-PD-1 Monoclonal Antibodies (mAbs) Are Superior to Anti-PD-L1 mAbs When Combined with Chemotherapy in First-Line Treatment for Metastatic Non-Small Cell Lung Cancer (mNSCLC): A Network Meta-Analysis

Platinum-based chemotherapy combined with anti-PD-1 or PD-L1 monoclonal antibodies (mAbs) is now standard first-line therapy for mNSCLC patients without sensitizing driver mutations. Anti-PD-1 and anti-PD-L1 mAbs are considered to be equivalent in efficacy. In the absence of head-to-head randomized control trials (RCTs), we utilized network meta-analysis (NWM) to provide an indirect comparison of their efficacy. A systematic literature review and NWM were performed using RCTs that investigated anti-PD-1 or PD-L1 mAbs ± chemotherapy in patients with mNSCLC in the first-line setting. The primary outcome was comparative overall survival (OS), while secondary outcomes were comparative progression-free survival (PFS), objective response rate (ORR), and rate of grade 3 and higher toxicities. We identified 24 RCTs. Patients treated with anti-PD-1 mAb + chemotherapy compared with anti-PD-L1 mAb + chemotherapy showed superior mOS, mPFS, and ORR with a similar rate of grade 3 and higher toxicities. This difference in mOS was most pronounced in the PD-L1 TPS 1-49% population. The two mAbs were equivalent as single agents. Anti-PD-1 mAb + chemotherapy improved mOS when compared to anti-PD-1 mAb monotherapy, whereas anti-PD-L1 mAbs + chemotherapy did not when compared to anti-PD-L1 mAb monotherapy. Head-to-head RCTs are warranted in the future.

Patterns of care in adult histone mutant gliomas: results of an international survey

Background

Histone mutant gliomas (HMG) with histone H3 K27 and G34 mutations are recognized as biologically discrete entities with distinct anatomical locations, a younger age at presentation (in comparison to the most common high grade gliomas, IDH wild type glioblastoma) and poor prognosis. There is a paucity of data regarding management of adult HMG patients and no consensus for management. This study aims to identify current patterns of Australian and US neuro-oncology clinical practice for this entity.

Methods

Following institutional approvals, a patterns of care questionnaire designed to capture relevant clinical variables was circulated through the Cooperative Trials Group for Neuro-Oncology (COGNO) in Australia and the Caris Precision Oncology Alliance in the United States (US).

Results

Between 4/2021 and 10/2021, 43 responses were collected. 33% (n=14) of responders tested all patients for HMGs routinely; 40.92% (n=18) tested in select patients 26% (n=11) did not test for HMGs. The common indications for testing selected patients were midline anatomic location (n=18) and age (n=11) (<50 years). 23 used molecular sequencing, 22 used IHC at their centres.

Nine participants stated knowledge of histone H3 mutation did not affect their management of these gliomas, 11 said it affected their management at the time of recurrence, 23 stated it affected management of midline K27M patients, 11 participants stated it affected management of K27M mutant gliomas in other locations and 3 felt it affected management of G34R/V mutant gliomas.

Conclusion

Here we present a description of how the discovery of a new molecular subtype of primary glial tumours, histone mutated gliomas in adults, is being introduced into clinical practice.

CSIG-13. CLINICAL IMPACT OF CDKN2A/B DELETIONS IN IDH-MUTANT ASTROCYTOMAS

BACKGROUND

IDH-mutant astrocytomas with CDKN2A/B homozygous deletions (HD) are now categorized as grade 4 astrocytomas. It is unclear how these HD astrocytomas should be treated. We aimed to compare 3-year outcomes for HD versus heterozygous deleted (HeD) IDH-mutant astrocytomas, describe the prognostic impact of deletions relative to histologic grade and describe differences in outcomes based on treatment regimen.

METHODS

Molecular and clinical data concerning IDH-mutant glioma patients +/-CDKN2A/B deletions were retrieved across four neuro-oncology centers and two tumor banks from 01/2016-07/2021.

RESULTS

48 patients with HD or HeD were identified. Median follow-up time was 4.0 years, median age 33 (range 20-74) years. Sixteen astrocytomas were histologic grade 4, remainder were grade 2 (n= 9) and grade 3 (n= 23). HD were detected in 16 patients. Survival data were unavailable in n= 1 HD and n= 2 HeD patients. 3-year OS for CDKN2A/B HD and HeD groups were 47% versus 67% (log-rank p= 0.004). For grades 2, 3 and 4, 3-year OS for HD were 100% (n= 1), 57% (n= 7) and 29% (n= 7) respectively, 3-year OS for HeD were 100% (n= 7), 56% (n= 16) and 57% (n= 7) respectively. In HD patients, six were treated with concurrent temozolomide-radiotherapy (3-year OS 50%) and five with radiotherapy and sequential temozolomide only (3-year OS 80%, log-rank p= 0.38). Treatment data were unavailable in two patients and three were treated with “other” regimens. Sequential regimens were preferentially used in histologic grade 2 and 3 cases.

CONCLUSION

Preliminary data are in keeping with current literature and are one of the first to describe outcomes based on clinical regimen. There was insufficient evidence of OS differences between concurrent and sequential therapy, though conclusions are limited by sample size and data maturity. Additional follow-up data are required to further define optimal treatment for these patients.

Therapeutic drug monitoring of osimertinib in EGFR mutant non-small cell lung cancer by dried blood spot and plasma collection: A pilot study

AIMS

Therapeutic drug monitoring (TDM) has led to significant improvements in individualized medical care, although its implementation in oncology has been limited to date. Tyrosine kinase inhibitors (TKIs) are a group of therapies for which TDM has been suggested. Osimertinib is one such therapy used in the treatment of epidermal growth factor receptor (EGFR) mutation-driven lung cancer. Herein, we describe a prospective pilot study involving 21 patients on osimertinib primarily as a preliminary evaluation of drug levels in a real-world setting.

METHODS

Concentrations of the drug and its primary metabolites were measured with a validated liquid chromatography-mass spectrometry (LC-MS) assay across serial timepoints. As part of this study, inter-individual variability by dose and ethnicity as well as intra-individual variability across timepoints are explored. Furthermore, we attempted to validate dried blood spot (DBS)-based quantitation as an accurate alternative to plasma quantitation.

RESULTS

Successful quantitation of osimertinib and primary metabolites was achieved for our subjects. Compound plasma levels were highly correlated to DBS levels. There was no significant difference in concentrations with ethnicity or dosing or intra-individual variability across timepoints.

CONCLUSIONS

As such, we demonstrate that TDM for osimertinib is practical for future trials. We also validated the use of DBS as an alternative to conventional quantitation for exploration of TDM for osimertinib in larger trials and for other targeted therapies.

Volumetric response and pattern of failure of histone altered high grade glioma in adults following management with radiation therapy

PURPOSE

H3K27M- and H3G34R-mutant gliomas are recently-classified subgroups of high-grade gliomas (HGGs) affecting younger adults. This study aimed to describe patterns of infiltration and failure, and the volumetric response of these tumours to radiotherapy.

METHODS

Patients with histone-mutant gliomas aged 16-50 years, managed from 2009 to 2021 were identified and clinical, radiological and histopathological characteristics collected. Tumour volume was assessed on MRI at diagnosis, pre-radiotherapy, month + 1, + 3 and + 5 post-radiation and at relapse.

RESULTS

Of 538 IDH1/2 wild-type HGGs, 18(15%) had a histone alteration. Eleven were H3K27M- and 7 H3G34R-mutant respectively. Median age at diagnosis was 20 years (range17-48 years). Median overall survival was 20 months (95%CI 14-29 months). Both H3K27M- and H3G34R-mutant tumours exhibited extensive T2F infiltration involving a median of 4 neuroanatomical subsites at diagnosis. Median volume of disease pre-radiotherapy on T1gd and T2F respectively was 0.5cm³ (IQR:0-1.7cm³) and 11.9 cm³ (IQR:7.5-29.6cm³) for H3K27M and 0.9cm³ (IQR:0-8.4cm³) and 43.8cm³ (IQR:25.2-86.6 cm³) for H3G34R tumours. T2F volume reduction > 50% was observed 3-months post-IMRT in 7(64%) patients with H3K27M and 1(14%) with H3G34R tumours. Fourteen patients had relapsed. Relapse was local-only, distant-only and both in 4(44%), 3(33%) and 2(22%) H3K27M-mutant and 1(20%), 2(40%), and 2(40%) H3G34R-mutant tumours. On last scan before death, leptomeningeal spread was present in 4/8(50%) and 1/5(20%) and subependymal spread in 4/8 (50%) and 0/5 H3K27M- and G34R-mutant cases respectively.

CONCLUSION

H3K27M-mutant gliomas are highly responsive to radiotherapy but exhibit high propensity for subsequent leptomeningeal and subependymal spread. H3G34R-mutant tumours exhibit lesser early volumetric response to radiotherapy and propensity for distant in-brain failure.

Interdependencies of the Neuronal, Immune and Tumor Microenvironment in Gliomas

Gliomas are the most common primary brain malignancy and are universally fatal. Despite significant breakthrough in understanding tumor biology, treatment breakthroughs have been limited. There is a growing appreciation that major limitations on effective treatment are related to the unique and highly complex glioma tumor microenvironment (TME). The TME consists of multiple different cell types, broadly categorized into tumoral, immune and non-tumoral, non-immune cells. Each group provides significant influence on the others, generating a pro-tumor dynamic with significant immunosuppression. In addition, glioma cells are highly heterogenous with various molecular distinctions on the cellular level. These variations, in turn, lead to their own unique influence on the TME. To develop future treatments, an understanding of this complex TME interplay is needed. To this end, we describe the TME in adult gliomas through interactions between its various components and through various glioma molecular phenotypes.

PSMA Expression Correlates with Improved Overall Survival and VEGF Expression in Glioblastoma

BACKGROUND

Glioblastomas are the most common and fatal primary brain malignancy in adults. There is a growing interest in identifying the molecular mechanisms of these tumors to develop novel treatments. Glioblastoma neo-angiogenesis is driven by VEGF, and another potential molecule linked to angiogenesis is PSMA. Our study suggests the potential for an association between PSMA and VEGF expression in glioblastoma neo-vasculature.

METHODS

Archived IDH1/2 wild-type glioblastomas were accessed; demographic and clinical outcomes were recorded. PSMA and VEGF expression by IHC were examined. Patients were dichotomized into PSMA expression high (3+) and low (0-2+) groups. The association between PSMA and VEGF expression was evaluated using Chi² analysis. OS in PSMA high and low expression groups were compared using multi-linear regression.

RESULTS

In total, 247 patients with IDH1/2 wild-type glioblastoma with archival tumor samples (between 2009-2014) were examined. PSMA expression correlated positively with VEGF expression (p = 0.01). We detected a significant difference in median OS between PSMA vascular endothelial expression high and low groups-16.1 and 10.8 months, respectively (p = 0.02).

CONCLUSION

We found a potential positive correlation between PSMA and VEGF expression. Secondly, we showed a potential positive correlation between PSMA expression and overall survival.