Recurrent paediatric ependymoma: a multicentre analysis of clinical features and tumour biology in the molecular era

Introduction: Ependymoma is the second most common malignant brain tumour of childhood. 50% of children with primary disease recur; three-quarters of these do not achieve long term survival. In the ‘molecular era’ of cancer research, diagnosis combines advanced molecular profiling with histopathological assessment. Whilst primary ependymomas can be classified based on epigenetic and transcriptomic features, there is little information on molecular signatures at recurrence. However, some small studies have implicated cancer immunity. Trials of novel therapies at recurrence have been disappointing. This study undertook molecular profiling of recurrent ependymoma, combined with contemporary clinical data, to better understand recurrence biology and potential therapy options. Methods: Clinical outcomes for 188 children with recurrent ependymoma were analysed. Cases with primary and matched recurrent samples were included in DNA methylation (n=56), RNA sequencing (n=52) and immunohistochemical (IHC) (n=56) analyses. RNA sequencing from FFPE tissue was validated to expand the cohort. Results: Recurrence was the strongest predictor of long term survival. Treatment approach at primary diagnosis was not associated with survival, but radiotherapy at first recurrence was associated with better short-term outcomes. Children with the commonest DNA methylation based diagnoses, EPN_PFA and EPN_RELA, had equally poor outcomes. RNA sequencing from FFPE tissue was effective, therefore tumours sequenced from FFPE and FF tissue were included in paired gene expression analyses. Transcriptomic and DNA methylation analyses identified three similar subgroups in FFPE and FF cohorts (PF1, PF2 and ST). At first recurrence, PF1 was associated with downregulated immune and inflammatory ontologies, which may indicate tumour immune escape. PF2 and ST subgroups demonstrated upregulation of ontologies associated with adaptive immunity. Despite this, there was little evidence of change in either immunogenicity or T-cell effector activity at first recurrence. IHC analysis identified a fall in inflammatory cells in posterior fossa tumours at recurrence and indicated that ependymoma is an immune excluded tumour. Conclusions: This study highlights both the abysmal prognosis for this disease, and the need for a better understanding of tumour biology to improve outcomes. This study has contributed novel data on changes at recurrence across molecular subgroups, and identified the immune excluded nature of ependymoma, which may be important in guiding therapy. The validation of RNA-seq from FFPE in childhood brain tumours has facilitated access to a large set of previously uninvestigated samples

Recurrent paediatric ependymoma: a multicentre analysis of clinical features and tumour biology in the molecular era

Introduction: Ependymoma is the second most common malignant brain tumour of childhood. 50% of children with primary disease recur; three-quarters of these do not achieve long term survival. In the ‘molecular era’ of cancer research, diagnosis combines advanced molecular profiling with histopathological assessment. Whilst primary ependymomas can be classified based on epigenetic and transcriptomic features, there is little information on molecular signatures at recurrence. However, some small studies have implicated cancer immunity. Trials of novel therapies at recurrence have been disappointing. This study undertook molecular profiling of recurrent ependymoma, combined with contemporary clinical data, to better understand recurrence biology and potential therapy options. Methods: Clinical outcomes for 188 children with recurrent ependymoma were analysed. Cases with primary and matched recurrent samples were included in DNA methylation (n=56), RNA sequencing (n=52) and immunohistochemical (IHC) (n=56) analyses. RNA sequencing from FFPE tissue was validated to expand the cohort. Results: Recurrence was the strongest predictor of long term survival. Treatment approach at primary diagnosis was not associated with survival, but radiotherapy at first recurrence was associated with better short-term outcomes. Children with the commonest DNA methylation based diagnoses, EPN_PFA and EPN_RELA, had equally poor outcomes. RNA sequencing from FFPE tissue was effective, therefore tumours sequenced from FFPE and FF tissue were included in paired gene expression analyses. Transcriptomic and DNA methylation analyses identified three similar subgroups in FFPE and FF cohorts (PF1, PF2 and ST). At first recurrence, PF1 was associated with downregulated immune and inflammatory ontologies, which may indicate tumour immune escape. PF2 and ST subgroups demonstrated upregulation of ontologies associated with adaptive immunity. Despite this, there was little evidence of change in either immunogenicity or T-cell effector activity at first recurrence. IHC analysis identified a fall in inflammatory cells in posterior fossa tumours at recurrence and indicated that ependymoma is an immune excluded tumour. Conclusions: This study highlights both the abysmal prognosis for this disease, and the need for a better understanding of tumour biology to improve outcomes. This study has contributed novel data on changes at recurrence across molecular subgroups, and identified the immune excluded nature of ependymoma, which may be important in guiding therapy. The validation of RNA-seq from FFPE in childhood brain tumours has facilitated access to a large set of previously uninvestigated samples

Translating childhood brain tumour research into clinical practice: the experience of molecular classification and diagnostics

Diagnosis and treatment of paediatric brain tumours has shown limited progress over the last half century. However, in the past 10 years the development of molecular techniques for investigating these tumours has expanded exponentially. The use of methylation profiling, gene expression analysis and the identification of gene fusions are forming the basis for improved diagnostic criteria and new treatment approaches. Knowledge and practice in this area is now beginning to expand beyond the research field and into the clinical setting. As the Chief Medical Officer highlighted in July 2017, an understanding of molecular medicine and its implications for both patients and the health economy is important for all clinicians. In this article, we summarise important recent advances in molecular medicine in childhood brain tumour research using the three most common types of paediatric brain tumour; pilocytic astrocytoma, medulloblastoma and ependymoma as illustrative examples

EPEN-08. THE TREM1 POSITIVE HYPOXIC MYELOID SUBPOPULATION IN POSTERIOR FOSSA EPENDYMOMA

We have previously shown the importance of immune factors in posterior fossa ependymoma (PF EPN). Recently, we found eight transcriptionally unique subpopulations of myeloid cells infiltrating PF EPN with one population particularly enriched in PFA1 tumors. This subpopulation, denoted as hypoxia myeloid subpopulation, is defined by genes associated with angiogenesis, hypoxia response, wound healing, cell migration, neutrophil activation, and response to oxygen levels. TREM1 (Triggering receptor expressed on myeloid cells 1) was found to be expressed almost exclusively within this hypoxia myeloid subpopulation. TREM1 encodes for a receptor belonging to the immunoglobulin superfamily that is expressed on myeloid cells, and stimulates neutrophil and monocyte inflammatory responses. However, single-cell RNAseq give little data suggesting location of cells within the tumor microenvironment. We performed immunohistochemistry (IHC) on our bank of ~90 FFPE PFA EPN samples using TREM1 to characterize and identify the location of the hypoxia myeloid cells. The TREM1 positive cells have an ambiguous cytomorphology reminiscent of a monocyte with modest cytoplasm and a mono-lobated nucleus. IHC also showed that TREM1+ myeloid cells are largely localized to the interface of necrosis and viable tissue, most frequently in a perivascular and intravascular distribution. The latter finding suggests that the TREM1+ cells are derived from the bone marrow and that they may be associated with the mesenchymal tumor population (MEC), which we have previously described as being enriched in PFA1 tumors and localizing to perinecrotic zones. This is supported by parallel IHC analysis of subpopulation-specific markers in the same cohort of PFA EPN which showed the highest TREM1 correlation was with CAIX, a marker of MEC. In PFA matched primary/recurrent pairs, the proportion of TREM1+ cells were increased at recurrence in the majority of cases, suggesting an evolving interaction between this TREM1+ hypoxia myeloid subpopulation and neoplastic cells over the disease course

Epen-23. A computational analysis of the tumour immune microenvironment in paediatric ependymoma

Ependymoma is the third commonest childhood brain tumour. Relapse is frequent, often fatal and current therapeutic strategies are inadequate. Previous ependymoma research describes an immunosuppressive environment with T-cell exhaustion, indicating a lack of response to T-cell directed immunotherapy. Understanding the immune microenvironment is therefore critical. We present a computational analysis of ependymoma, gene expression derived, immune profiles. Using 465 ependymoma samples from gene expression datasets (GSE64415, GSE50385, GSE100240) and two RNA-seq databases from UK ependymomas, we applied bulk tumour deconvolution methods (CIBERSORT and xCell) to infer immune cell populations. Additionally, we measured checkpoint blockade related mRNAs and used immunohistochemistry to investigate cell populations in ependymoma sections. CIBERSORT indicated high proportions of M2-like macrophages and smaller proportions of activated natural killer (NK) cells, T follicular helper cells, CD4+ memory T-cells and B-cells. xCell overlapped with the M2-like macrophage and CD4+ memory T-cell signatures seen in CIBERSORT. On immunohistochemistry, T and B cells were scarce, with small numbers of CD8+, CD4+ and CD20+ cells in the parenchyma but greater numbers in surrounding regions. CD68 was more highly expressed in the parenchyma. Analysis of nine checkpoint ligands and receptors demonstrated only the TIM3/GAL9 combination was reliably detectable. GAL9 is implicated in tumour interactions with T-cells and macrophages elsewhere, possibly contributing to poorer outcomes. Our study supports the presence of myeloid cells being leading contributors to the ependymoma immune microenvironment. Further work will delineate the extent of myeloid contribution to immunosuppression across molecular subtypes. Modulation of tumour immunity may contribute to better clinical outcomes

Phase II study of intravenous etoposide in patients with relapsed ependymoma (CNS 2001 04)

BackgroundRelapsed ependymoma has a dismal prognosis, and the role of chemotherapy at relapse remains unclear. This study prospectively evaluated the efficacy of intensive intravenous (IV) etoposide in patients less than 21 years of age with relapsed intracranial ependymoma (NCT00278252).MethodsThis was a single-arm, open-label, phase II trial using Gehan’s two-stage design. Patients received IV etoposide 100 mg/m2 on days 1-3, 8-10, and 15-17 of each 28-day cycle, up to maximum of 6 cycles. Primary outcome was radiological response after 3 cycles. Pharmacokinetic analysis was performed in 10 patients.ResultsTwenty-five patients were enrolled and included in the intention-to-treat (ITT) analysis. Three patients were excluded in per-protocol (PP) analysis. After 3 cycles of etoposide, 5 patients (ITT 20%/PP 23%) had a complete response (CR), partial response (PR), or objective response (OR). Nine patients (ITT 36%/PP 41%,) had a best overall response of CR, PR, or OR. 1-year PFS was 24% in ITT and 23% in PP populations. 1-year OS was 56% and 59%, 5-year OS was 20% and 18%, respectively, in ITT and PP populations. Toxicity was predominantly hematological, with 20/25 patients experiencing a grade 3 or higher hematological adverse event.ConclusionsThis study confirms the activity of IV etoposide against relapsed ependymoma, however, this is modest, not sustained, and similar to that with oral etoposide, albeit with increased toxicity. These results confirm the dismal prognosis of this disease, provide a rationale to include etoposide within drug combinations, and highlight the need to develop novel treatments for recurrent ependymoma

Multicentre service evaluation of presentation of newly diagnosed cancers and type 1 diabetes in children in the UK during the COVID-19 pandemic

Background: The COVID-19 pandemic led to changes in patterns of presentation to emergency departments. Child health professionals were concerned that this could contribute to the delayed diagnosis of life-threatening conditions, including childhood cancer (CC) and type 1 diabetes (T1DM). Our multicentre, UK-based service evaluation assessed diagnostic intervals and disease severity for these conditions.Methods: We collected presentation route, timing and disease severity for children with newly diagnosed CC in three principal treatment centres and T1DM in four centres between 1 January and 31 July 2020 and the corresponding period in 2019. Total diagnostic interval (TDI), patient interval (PI), system interval (SI) and disease severity across different time periods were compared.Results: For CCs and T1DM, the route to diagnosis and severity of illness at presentation were unchanged across all time periods. Diagnostic intervals for CCs during lockdown were comparable to that in 2019 (TDI 4.6, PI 1.1 and SI 2.1 weeks), except for an increased PI in January–March 2020 (median 2.7 weeks). Diagnostic intervals for T1DM during lockdown were similar to that in 2019 (TDI 16 vs 15 and PI 14 vs 14 days), except for an increased PI in January–March 2020 (median 21 days).Conclusions: There is no evidence of diagnostic delay or increased illness severity for CC or T1DM, during the first phase of the pandemic across the participating centres. This provides reassuring data for children and families with these life-changing conditions

Toward Improved Diagnosis Accuracy and Treatment of Children, Adolescents, and Young Adults With Ependymoma: The International SIOP Ependymoma II Protocol

Background: The clinical management of ependymoma in childhood and adolescence is complex and the clinicobiopathological correlates of outcome remain poorly understood. This international SIOP Ependymoma II (SIOP EPII) trial aims to improve the outcome of patients with ependymoma. Methods: SIOP EPII includes any patient <22 years at diagnosis with ependymoma, stratified by age, tumor location, and outcome of the initial surgery. Centralized pathology and imaging is required for diagnosis confirmation. SIOP EPII included three randomized studies according to age, postoperative residue, and suitability to receive radiotherapy. Patients ineligible for interventional strata are followed-up in an observational study. The staging phase aims to determine if central neurosurgical and radiological postoperative MRI reviews increase the resection rate. Patients ≥12 months with (i) no residual disease are randomly assigned in a phase III trial to evaluate the efficacy of post-radiation 16-week chemotherapy (VEC + CDDP) on PFS (stratum I); (ii) centrally confirmed measurable inoperable residual disease are allocated to randomized frontline chemotherapy phase II study (VEC vs. VEC + high-dose methotrexate) and considered for a second-look surgery (stratum II). If second-look surgery is not feasible or tumor residuum remains, patients receive 8 Gy-boost radiotherapy after conformal radiotherapy (phase I). (iii) Patients < 12 months (18 months in the UK) or not eligible to receive radiotherapy are randomized in a phase II study to receive chemotherapy (alternated myelosuppressive and nonmyelosuppressive chemotherapy), with or without valproate (stratum III). To overcome the limitations encountered in the preliminary conclusions of the ACNS-0831 study, a SIOP EPII dedicated on-study amendment has been planned to definitively conclude the relevance of maintenance chemotherapy in stratum I. Secondary outcomes include overall survival, quality of life, neuropsychological and neuroendocrine outcomes, safety, and identification of key prognostic biomarkers (BIOMECA). Clinical Trial Registration: ClinicalTrials.gov, identifier: NCT02265770

EPEN-11. TUMOR DIFFERENTIATION IMPACTS THE BIOLOGY OF RECURRENCE IN CHILDHOOD POSTERIOR FOSSA EPENDYMOMA

Ependymoma (EPN) of childhood is curable in only 50% of cases, with recurrences in the remainder that are refractory to treatment. In recent years significant advances have been made in understanding the molecular and cellular biology of EPN. Recent studies show that PFA subgroup EPN are comprised of multiple neoplastic subpopulations that show undifferentiated, differentiated and mesenchymal characteristics. These studies focused on tumor at presentation, with recurrent EPN being less well understood. In the present longitudinal study we examine changes in neoplastic cell heterogeneity in serial presentations of PFA EPN using deconvolution (Cibersort) of bulk RNAseq data. Analysis of a cohort of 48 PFA EPN presenting at Children’s Colorado showed survival and PFA1/PFA2 subtype assignment was associated with the proportion of individual neoplastic subpopulations as determined by deconvolution. Tumors that subsequently regrew had a significantly higher estimated proportion of undifferentiated EPN cells (UEC) at presentation, than those that were non-recurrent after 5 years follow-up. This outcome association potentially age related, as UEC proportions are significantly higher in PFA arising in children < 1 year old who have a particularly poor prognosis. Changes in PFA neoplastic subpopulations at recurrence was performed in two cohorts of patients from Children’s Colorado (n=23) and Nottingham, UK (n=15). As a whole, no subpopulation proportion was significantly changed at recurrence. However, separation of PFA into subtypes PFA1 and PFA2 revealed an increase in the proportion of the cilia-differentiated EPN cell subpopulation is more frequent event in PFA1 (15/24), and rare in PFA2 (2/11). Changes in other neoplastic subpopulations at recurrence were smaller and only seen in PFA1, both UEC and mesenchymal subpopulations being lower at recurrence. In summary, only PFA1 showed dynamic changes in neoplastic subpopulation proportions at recurrence, with potential impacts on transcriptomic based-subgroup assignment, whereas PFA2 proportions remained largely stable