Survivors of infant atypical teratoid/rhabdoid tumors present with severely impaired cognitive functions especially for fluid intelligence and visual processing: data from the German brain tumor studies

BACKGROUND

The contribution of tumor type, multimodal treatment, and other patient-related factors upon long-term cognitive sequelae in infant brain tumor survivors remains undefined. We add our retrospective analysis of neuropsychological and quality of survival (QoS) outcome data of survivors of atypical teratoid/rhabdoid tumors (ATRT) and extracranial malignant rhabdoid tumors of the soft tissues (eMRT) and kidneys (RTK) treated within the same framework. Neuropsychological data from children with ATRT were compared to data from children with non-irradiated low-grade glioma (LGG).

PATIENTS AND METHODS

Following surgery, patients (0-36 months at diagnosis) had received radio-chemotherapy (up to 54 Gy; ATRT: n = 13; eMRT/RTK: n = 7), chemotherapy only (LGG: n = 4; eMRT/RTK: n = 1) or had been observed (LGG: n = 11). Neuropsychological evaluation employing comparable tests was performed at median 6.8 years (ATRT), 6.6 years (eMRT/RTK), and 5.2 years (LGG) post diagnosis.

RESULTS

We detected sequelae in various domains for all tumor types. Group comparison showed impairments, specifically in fluid intelligence (p = .041; d = 1.11) and visual processing (p = .001; d = 2.09) in ATRT patients when compared to LGG patients. Results for psychomotor speed and attention abilities were significantly below the norm for both groups (p < .001-.019; d = 0.79-1.90). Diagnosis predicted impairments of cognitive outcome, while sex- and age-related variables did not. QoS outcome for all rhabdoid patients displayed impairments mainly in social (p = .008; d = 0.74) and school functioning (p = .048; d = 0.67), as well as lower overall scores in psychosocial functioning (p = .023; d = 0.78) and quality of life (p = .006; d = 0.79) compared to healthy controls.

CONCLUSION

Survivors of infant ATRT experience various late effects in cognition and QoS following multimodal treatment, while infant LGG patients without radiotherapy demonstrated comparable impairments in psychomotor and attention abilities. Early onset and multimodal treatment of rhabdoid tumors require close monitoring of neuropsychological and QoS sequelae.

Treatment response as surrogate to predict risk for disease progression in pediatric medulloblastoma with persistent MRI lesions after first-line treatment

BACKGROUND

This study aims at clarifying the impact of persistent residual lesions following first-line treatment for pediatric medulloblastoma.

METHODS

Data on 84 pediatric patients with medulloblastoma and persistent residual lesions on centrally reviewed MRI at the end of first-line therapy were analyzed.

RESULTS

Twenty patients (23.8%) had residual lesions in the tumor bed (R+/M0), 51 (60.7%) had distant lesions (R0/M+) and 13 (15.5%) had both (R+/M+). Overall response to first-line therapy was minor or partial (≥25% reduction, MR/PR) for 64 (76.2%) and stable disease (SD) for 20 patients (23.8%). Five-year post-primary-treatment progression-free (pptPFS) and overall survival (pptOS) were superior after MR/PR (pptPFS: 62.5±7.0%[MR/PR] vs. 35.9±12.8%[SD], p=0.03; pptOS: 79.7±5.9[MR/PR] vs. 55.5±13.9[SD], p=0.04). Further, R+/M+ was associated with a higher risk for progression (5-year pptPFS: 22.9±17.9%[R+,M+] vs. 72.4±12.0%[R+,M0]; p=0.03). Watch-and-wait was pursued in 58 patients, while n=26 received additional treatments (chemotherapy only, n=19; surgery only, n=2; combined, n=3; valproic acid, n=2), and their outcomes were not superior to watch-and-wait (5-year pptPFS: 58.5±7.7% vs. 51.6±10.7% p=0.71; 5-year pptOS: 76.3±6.9% vs. 69.8±9.7%, p=0.74). For the whole cohort, five-year pptPFS by molecular subgroup (58 cases) were WNT: 100%, SHH: 50.0±35.4%, Group-4, 52.5±10.5, Group-3 54.2±13.8%; (p=0.08).

CONCLUSION

Overall response and extent of lesions can function as surrogate parameters to predict outcomes in pediatric MB patients with persistent lesions after first-line therapy. Especially in case of solitary persistent medulloblastoma MRI lesion, additional therapy was not beneficial. Therefore, treatment response, extent/kind of residual lesions and further diagnostic information needs consideration for indication of additional treatments for persisting lesions.

Transcriptomic and epigenetic dissection of spinal ependymoma (SP-EPN) identifies clinically relevant subtypes enriched for tumors with and without NF2 mutation

Ependymomas encompass multiple clinically relevant tumor types based on localization and molecular profiles. Tumors of the methylation class "spinal ependymoma" (SP-EPN) represent the most common intramedullary neoplasms in children and adults. However, their developmental origin is ill-defined, molecular data are scarce, and the potential heterogeneity within SP-EPN remains unexplored. The only known recurrent genetic events in SP-EPN are loss of chromosome 22q and NF2 mutations, but neither types and frequency of these alterations nor their clinical relevance have been described in a large, epigenetically defined series. Transcriptomic (n = 72), epigenetic (n = 225), genetic (n = 134), and clinical data (n = 112) were integrated for a detailed molecular overview on SP-EPN. Additionally, we mapped SP-EPN transcriptomes to developmental atlases of the developing and adult spinal cord to uncover potential developmental origins of these tumors. The integration of transcriptomic ependymoma data with single-cell atlases of the spinal cord revealed that SP-EPN display the highest similarities to mature adult ependymal cells. Unsupervised hierarchical clustering of transcriptomic data together with integrated analysis of methylation profiles identified two molecular SP-EPN subtypes. Subtype A tumors primarily carried previously known germline or sporadic NF2 mutations together with 22q loss (bi-allelic NF2 loss), resulting in decreased NF2 expression. Furthermore, they more often presented as multilocular disease and demonstrated a significantly reduced progression-free survival as compared to SP-EP subtype B. In contrast, subtype B predominantly contained samples without NF2 mutation detected in sequencing together with 22q loss (monoallelic NF2 loss). These tumors showed regular NF2 expression but more extensive global copy number alterations. Based on integrated molecular profiling of a large multi-center cohort, we identified two distinct SP-EPN subtypes with important implications for genetic counseling, patient surveillance, and drug development priorities.

Classification of Brain Tumors by Nanopore Sequencing of Cell-Free DNA from Cerebrospinal Fluid

BACKGROUND

Molecular brain tumor diagnosis is usually dependent on tissue biopsies or resections. This can pose several risks associated with anesthesia or neurosurgery, especially for lesions in the brain stem or other difficult-to-reach anatomical sites. Apart from initial diagnosis, tumor progression, recurrence, or the acquisition of novel genetic alterations can only be proven by re-biopsies.

METHODS

We employed Nanopore sequencing on cell-free DNA (cfDNA) from cerebrospinal fluid (CSF) and analyzed copy number variations (CNV) and global DNA methylation using a random forest classifier. We sequenced 129 samples with sufficient DNA. These samples came from 99 patients and encompassed 22 entities. Results were compared to clinical diagnosis and molecular analysis of tumor tissue, if available.

RESULTS

110/129 samples were technically successful, and 50 of these contained detectable circulating tumor DNA (ctDNA) by CNV or methylation profiling. ctDNA was detected in samples from patients with progressive disease but also from patients without known residual disease. CNV plots showed diagnostic and prognostic alterations, such as C19MC amplifications in embryonal tumors with multilayered rosettes or Chr.1q gains and Chr.6q losses in posterior fossa group A ependymoma, respectively. Most CNV profiles mirrored the profiles of the respective tumor tissue. DNA methylation allowed exact classification of the tumor in 22/110 cases and led to incorrect classification in 2/110 cases. Only 5/50 samples with detected ctDNA contained tumor cells detectable through microscopy.

CONCLUSIONS

Our results suggest that Nanopore sequencing data of cfDNA from CSF samples may be a promising approach for initial brain tumor diagnostics and an important tool for disease monitoring.

Pineal anlage tumor: clinical and diagnostic features, and rationales for treatment

PURPOSE

To provide a treatment-focused review and develop basic treatment guidelines for patients diagnosed with pineal anlage tumor (PAT).

METHODS

Prospectively collected data of three patients with pineal anlage tumor from Germany was combined with clinical details and treatment information from 17 published cases.

RESULTS

Overall, 20 cases of PAT were identified (3 not previously reported German cases, 17 cases from published reports). Age at diagnosis ranged from 0.3 to 35.0 (median: 3.2 ± 7.8) years. All but three cases were diagnosed before the age of three years. For three cases, metastatic disease at initial staging was described. All patients underwent tumor surgery (gross-total resection: 9, subtotal resection/biopsy: 9, extent of resection unknown: 2). 15/20 patients were alive at last follow-up. Median follow-up for 10/15 surviving patients with available follow-up and treatment data was 2.4 years (0.3-6.5). Relapse was reported for 3 patients within 0.8 years after diagnosis. Five patients died, 3 after relapse and 2 from early postoperative complications. Two-year-progression-free- and -overall survival were 65.2 ± 12.7% and 49.2 ± 18.2%, respectively. All 4 patients who received intensive chemotherapy including high-dose chemotherapy combined with radiotherapy (2 focal, 2 craniospinal [CSI]) had no recurrence. Focal radiotherapy- and CSI-free survival rates in 13 evaluable patients were 46.2% (6/13) and 61.5% (8/13), respectively.

CONCLUSION

PAT is an aggressive disease mostly affecting young children. Therefore, adjuvant therapy using intensive chemotherapy and considering radiotherapy appears to comprise an appropriate treatment strategy. Reporting further cases is crucial to evaluate distinct treatment strategies.

Child-centredness in paediatric magnetic resonance imaging: Information needs and experiences of children requiring magnetic resonance imaging and their parents

BACKGROUND

Assessing patient experiences is essential to provide high quality health-care. The objectives of this study were to examine (1) child- and parent-reported information status before magnetic resonance imaging (MRI), (2) experiences during an MRI and (3) needs and suggestions for improvement.

METHODS

Children (≥8 years) and parents answered questionnaires (before and after planned MRI examination) covering mental condition, information status/needs, preparation for MRI, and potential stressors. Before MRI n = 132 accompanying parents and n = 91 children provided data (after MRI: n = 93 parents; n = 71 children). The mean age of the children undergoing MRI was 10.5 years (SD = 4.9). Children had on average seven previous MRIs before our survey (Range: 1-33). Twenty-three percent of the children were to be sedated during the examination.

RESULTS

Parents and children reported low to medium levels of burden, high knowledge and high information status. For the children, most stressful factors during the MRI were boredom and noise. Main information resources were the radiologists or self-searches. Parents of children with their first MRI reported higher anxiety levels in their children and stated a worse information status (main information source: self-searches/internet). Parents reported needs regarding organization of the MRI (e.g., reduction of waiting times), age-appropriate information and communication during the MRI. Children wished to visit the MRI room prior the examination (44%) and to get more information (44%). Children suggested improvements such as better sound quality of films/music, more transparency about the procedure, being in contact with a parent and shorter examinations.

CONCLUSION

Results suggest that preparation, information provision and care is perceived positively by families. Needs and suggestions for improvement were, for example, higher transparency of procedures, better communication and reduction of stress. Findings indicate that preparation in routine-care should follow an individualized child-focused approach, should focus on families without previous MRIs and should address children with high anxiety levels.

Clinical outcome of pediatric medulloblastoma patients with Li-Fraumeni syndrome

BACKGROUND

The prognosis for Li-Fraumeni syndrome (LFS) patients with medulloblastoma (MB) is poor. Comprehensive clinical data for this patient group is lacking, challenging the development of novel therapeutic strategies. Here, we present clinical and molecular data on a retrospective cohort of pediatric LFS MB patients.

METHODS

In this multinational, multicenter retrospective cohort study, LFS patients under 21 years with MB and class 5 or class 4 constitutional TP53 variants were included. TP53 mutation status, methylation subgroup, treatment, progression free- (PFS) and overall survival (OS), recurrence patterns, and incidence of subsequent neoplasms were evaluated.

RESULTS

The study evaluated 47 LFS individuals diagnosed with MB, mainly classified as DNA methylation subgroup "SHH_3" (86%). The majority (74%) of constitutional TP53 variants represented missense variants. The 2- and 5-year (y-) PFS were 36% and 20%, and 2- and 5y-OS were 53% and 23%, respectively. Patients who received postoperative radiotherapy (RT) (2y-PFS: 44%, 2y-OS: 60%) or chemotherapy before RT (2y-PFS: 32%, 2y-OS: 48%) had significantly better clinical outcome then patients who were not treated with RT (2y-PFS: 0%, 2y-OS: 25%). Patients treated according to protocols including high-intensity chemotherapy and patients who received only maintenance-type chemotherapy showed similar outcomes (2y-PFS: 42% and 35%, 2y-OS: 68% and 53%, respectively).

CONCLUSIONS

LFS MB patients have a dismal prognosis. In the presented cohort use of RT significantly increased survival rates, whereas chemotherapy intensity did not influence their clinical outcome. Prospective collection of clinical data and development of novel treatments are required to improve the outcome of LFS MB patients.

Mouse models of pediatric high-grade gliomas with MYCN amplification reveal intratumoral heterogeneity and lineage signatures

Pediatric high-grade gliomas of the subclass MYCN (HGG-MYCN) are highly aggressive tumors frequently carrying MYCN amplifications, TP53 mutations, or both alterations. Due to their rarity, such tumors have only recently been identified as a distinct entity, and biological as well as clinical characteristics have not been addressed specifically. To gain insights into tumorigenesis and molecular profiles of these tumors, and to ultimately suggest alternative treatment options, we generated a genetically engineered mouse model by breeding hGFAP-cre::Trp53Fl/Fl::lsl-MYCN mice. All mice developed aggressive forebrain tumors early in their lifetime that mimic human HGG-MYCN regarding histology, DNA methylation, and gene expression. Single-cell RNA sequencing revealed a high intratumoral heterogeneity with neuronal and oligodendroglial lineage signatures. High-throughput drug screening using both mouse and human tumor cells finally indicated high efficacy of Doxorubicin, Irinotecan, and Etoposide as possible therapy options that children with HGG-MYCN might benefit from.

Risk prediction in early childhood sonic hedgehog medulloblastoma treated with radiation-avoiding chemotherapy: Evidence for more than 2 subgroups

BACKGROUND

The prognostic impact of clinical risk factors and DNA methylation patterns in sonic hedgehog (SHH)-activated early childhood desmoplastic/nodular medulloblastoma (DMB) or medulloblastoma with extensive nodularity (MBEN) were evaluated to better identify patients at risk for relapse.

METHODS

One hundred and forty-four patients with DMB (n = 99) or MBEN (n = 45) aged <5 years and treated with radiation-sparing approaches, including intraventricular methotrexate in 132 patients were evaluated.

RESULTS

Patients with DMB had less favorable 5-year progression-free survival than MBEN (5y-PFS, 71% [DMB] vs. 93% [MBEN]). Patients aged >3 years were associated with more unfavorable 5y-PFS (47% [>3 years] vs. 85% [<1 year] vs. 84% [1-3 years]). DNA methylation profiles available (n = 78) were reclassified according to the 2021 WHO classification into SHH-1 (n = 39), SHH-2 (n = 38), and SHH-3 (n = 1). Hierarchical clustering delineated 2 subgroups among SHH-2: SHH-2a (n = 19) and SHH-2b (n = 19). Patients with SHH-2b medulloblastoma were older, predominantly displayed DMB histology, and were more often located in the cerebellar hemispheres. Chromosome 9q losses were more frequent in SHH-2b, while few chromosomal alterations were observed in SHH-2a. SHH-2b medulloblastoma carried a significantly increased relapse risk (5y-PFS: 58% [SHH-2b] vs. 83% [SHH-1] vs. 95% [SHH-2a]). Subclassification of SHH-2 with key clinical and cytogenetic characteristics was confirmed using 2 independent cohorts (total n = 188). Gene mutation analysis revealed a correlation of SHH-2a with SMO mutations.

CONCLUSIONS

These data suggest further heterogeneity within early childhood SHH-DMB/MBEN: SHH-2 splits into a very low-risk group SHH-2a enriched for MBEN histology and SMO mutations, and SHH-2b comprising older DMB patients with a higher risk of relapse.

Mitochondrial DNA mutations in Medulloblastoma

To date, several studies on genomic events underlying medulloblastoma (MB) biology have expanded our understanding of this tumour entity and led to its division into four groups-WNT, SHH, group 3 (G3) and group 4 (G4). However, there is little information about the relevance of pathogenic mitochondrial DNA (mtDNA) mutations and their consequences across these. In this report, we describe the case of a female patient with MB and a mitochondriopathy, followed by a study of mtDNA variants in MB groups. After being diagnosed with G4 MB, the index patient was treated in line with the HIT 2000 protocol with no indications of relapse after five years. Long-term side effects of treatment were complemented by additional neurological symptoms and elevated lactate levels ten years later, resulting in suspected mitochondrial disease. This was confirmed by identifying a mutation in the MT-TS1 gene which appeared homoplasmic in patient tissue and heteroplasmic in the patient's mother. Motivated by this case, we explored mtDNA mutations across 444 patients from ICGC and HIT cohorts. While there was no statistically significant enrichment of mutations in one MB group, both cohorts encompassed a small group of patients harbouring potentially deleterious mtDNA variants. The case presented here highlights the possible similarities between sequelae caused by MB treatment and neurological symptoms of mitochondrial dysfunction, which may apply to patients across all MB groups. In the context of the current advances in characterising and interpreting mtDNA aberrations, recognising affected patients could enhance our future knowledge regarding the mutations' impact on carcinogenesis and cancer treatment.

Group-specific cellular metabolism in Medulloblastoma

BACKGROUND

Cancer metabolism influences multiple aspects of tumorigenesis and causes diversity across malignancies. Although comprehensive research has extended our knowledge of molecular subgroups in medulloblastoma (MB), discrete analysis of metabolic heterogeneity is currently lacking. This study seeks to improve our understanding of metabolic phenotypes in MB and their impact on patients' outcomes.

METHODS

Data from four independent MB cohorts encompassing 1,288 patients were analysed. We explored metabolic characteristics of 902 patients (ICGC and MAGIC cohorts) on bulk RNA level. Moreover, data from 491 patients (ICGC cohort) were searched for DNA alterations in genes regulating cell metabolism. To determine the role of intratumoral metabolic differences, we examined single-cell RNA-sequencing (scRNA-seq) data from 34 additional patients. Findings on metabolic heterogeneity were correlated to clinical data.

RESULTS

Established MB groups exhibit substantial differences in metabolic gene expression. By employing unsupervised analyses, we identified three clusters of group 3 and 4 samples with distinct metabolic features in ICGC and MAGIC cohorts. Analysis of scRNA-seq data confirmed our results of intertumoral heterogeneity underlying the according differences in metabolic gene expression. On DNA level, we discovered clear associations between altered regulatory genes involved in MB development and lipid metabolism. Additionally, we determined the prognostic value of metabolic gene expression in MB and showed that expression of genes involved in metabolism of inositol phosphates and nucleotides correlates with patient survival.

CONCLUSION

Our research underlines the biological and clinical relevance of metabolic alterations in MB. Thus, distinct metabolic signatures presented here might be the first step towards future metabolism-targeted therapeutic options.

[Pediatric Intracranial Ependymoma - Recommendations for First-Line Treatment from the German HIT-MED study group]

Biological subtypes of ependymoma (EPN) have been introduced by the recent WHO classification and appear to have great impact on the clinical course, but have not yet found their way into clinical risk stratification. Further, the overall unfavorable prognosis underlines the fact that current therapeutic strategies need further evaluation for improvement. To date, there is no international consensus regarding first-line treatment for children with intracranial EPN. Extent of resection is known to be the most important clinical risk factor, leading to the consensus that consequent evaluation for re-surgery of postoperative residual tumor needs to have highest priority. Furthermore, efficacy of local irradiation is unquestioned and recommended for patients aged>1 year. In contrast, efficacy of chemotherapy is still under discussion. The European trial SIOP Ependymoma II aims at evaluating efficacy of different chemotherapy elements, leading to the recommendation to include German patients. The BIOMECA study, as biological accompanying study, aims at identifying new prognostic parameters. These results might help to develop targeted therapies for unfavorable biological subtypes. For patient who are not qualified for inclusion into the interventional strata, the HIT-MED Guidance 5.2 provides specific recommendations. This article is meant as an overview of national guidelines regarding diagnostics and treatment as well as of treatment according to the SIOP Ependymoma II trial protocol.

Transcriptome analysis stratifies second-generation non-WNT/non-SHH medulloblastoma subgroups into clinically tractable subtypes

Medulloblastoma (MB), one of the most common malignant pediatric brain tumor, is a heterogenous disease comprised of four distinct molecular groups (WNT, SHH, Group 3, Group 4). Each of these groups can be further subdivided into second-generation MB (SGS MB) molecular subgroups, each with distinct genetic and clinical characteristics. For instance, non-WNT/non-SHH MB (Group 3/4) can be subdivided molecularly into eight distinct and clinically relevant tumor subgroups. A further molecular stratification/summarization of these SGS MB would allow for the assignment of patients to risk-associated treatment protocols. Here, we performed DNA- and RNA-based analysis of 574 non-WNT/non-SHH MB and analyzed the clinical significance of various molecular patterns within the entire cohort and the eight SGS MB, with the aim to develop an optimal risk stratification of these tumors. Multigene analysis disclosed several survival-associated genes highly specific for each molecular subgroup within this non-WNT/non-SHH MB cohort with minimal inter-subgroup overlap. These subgroup-specific and prognostically relevant genes were associated with pathways that could underlie SGS MB clinical-molecular diversity and tumor-driving mechanisms. By combining survival-associated genes within each SGS MB, distinct metagene sets being appropriate for their optimal risk stratification were identified. Defined subgroup-specific metagene sets were independent variables in the multivariate models generated for each SGS MB and their prognostic value was confirmed in a completely non-overlapping validation cohort of non-WNT/non-SHH MB (n = 377). In summary, the current results indicate that the integration of transcriptome data in risk stratification models may improve outcome prediction for each non-WNT/non-SHH SGS MB. Identified subgroup-specific gene expression signatures could be relevant for clinical implementation and survival-associated metagene sets could be adopted for further SGS MB risk stratification. Future studies should aim at validating the prognostic role of these transcriptome-based SGS MB subtypes in prospective clinical trials.

Multiomic neuropathology improves diagnostic accuracy in pediatric neuro-oncology

The large diversity of central nervous system (CNS) tumor types in children and adolescents results in disparate patient outcomes and renders accurate diagnosis challenging. In this study, we prospectively integrated DNA methylation profiling and targeted gene panel sequencing with blinded neuropathological reference diagnostics for a population-based cohort of more than 1,200 newly diagnosed pediatric patients with CNS tumors, to assess their utility in routine neuropathology. We show that the multi-omic integration increased diagnostic accuracy in a substantial proportion of patients through annotation to a refining DNA methylation class (50%), detection of diagnostic or therapeutically relevant genetic alterations (47%) or identification of cancer predisposition syndromes (10%). Discrepant results by neuropathological WHO-based and DNA methylation-based classification (30%) were enriched in histological high-grade gliomas, implicating relevance for current clinical patient management in 5% of all patients. Follow-up (median 2.5 years) suggests improved survival for patients with histological high-grade gliomas displaying lower-grade molecular profiles. These results provide preliminary evidence of the utility of integrating multi-omics in neuropathology for pediatric neuro-oncology.

Outcomes of Infants and Young Children With Relapsed Medulloblastoma After Initial Craniospinal Irradiation-Sparing Approaches: An International Cohort Study

PURPOSE

Infant and young childhood medulloblastoma (iMB) is usually treated without craniospinal irradiation (CSI) to avoid neurocognitive late effects. Unfortunately, many children relapse. The purpose of this study was to assess salvage strategies and prognostic features of patients with iMB who relapse after CSI-sparing therapy.

METHODS

We assembled a large international cohort of 380 patients with relapsed iMB, age younger than 6 years, and initially treated without CSI. Univariable and multivariable Cox models of postrelapse survival (PRS) were conducted for those treated with curative intent using propensity score analyses to account for confounding factors.

RESULTS

The 3-year PRS, for 294 patients treated with curative intent, was 52.4% (95% CI, 46.4 to 58.3) with a median time to relapse from diagnosis of 11 months. Molecular subgrouping was available for 150 patients treated with curative intent, and 3-year PRS for sonic hedgehog (SHH), group 4, and group 3 were 60%, 84%, and 18% (P = .0187), respectively. In multivariable analysis, localized relapse (P = .0073), SHH molecular subgroup (P = .0103), CSI use after relapse (P = .0161), and age ≥ 36 months at initial diagnosis (P = .0494) were associated with improved survival. Most patients (73%) received salvage CSI, and although salvage chemotherapy was not significant in multivariable analysis, its use might be beneficial for a subset of children receiving salvage CSI < 35 Gy (P = .007).

CONCLUSION

A substantial proportion of patients with relapsed iMB are salvaged after initial CSI-sparing approaches. Patients with SHH subgroup, localized relapse, older age at initial diagnosis, and those receiving salvage CSI show improved PRS. Future prospective studies should investigate optimal CSI doses and the role of salvage chemotherapy in this population.

G2 checkpoint targeting via Wee1 inhibition radiosensitizes EGFRvIII-positive glioblastoma cells

BACKGROUND

The gene of the Epidermal growth factor receptor (EGFR) is one of the most frequently altered genes in glioblastoma (GBM), with deletions of exons 2-7 (EGFRvIII) being amongst the most common genomic mutations. EGFRvIII is heterogeneously expressed in GBM. We already showed that EGFRvIII expression has an impact on chemosensitivity, replication stress, and the DNA damage response. Wee1 kinase is a major regulator of the DNA damage induced G2 checkpoint. It is highly expressed in GBM and its overexpression is associated with poor prognosis. Since Wee1 inhibition can lead to radiosensitization of EGFRvIII-negative (EGFRvIII-) GBM cells, we asked, if Wee1 inhibition is sufficient to radiosensitize also EGFRvIII-positive (EGFRvIII+) GBM cells.

METHODS

We used the clinically relevant Wee1 inhibitor adavosertib and two pairs of isogenetic GBM cell lines with and without endogenous EGFRvIII expression exhibiting different TP53 status. Moreover, human GBM samples displaying heterogenous EGFRvIII expression were analyzed. Expression of Wee1 was assessed by Western blot and respectively immunohistochemistry. The impact of Wee1 inhibition in combination with irradiation on cell cycle and cell survival was analyzed by flow cytometry and colony formation assay.

RESULTS

Analysis of GBM cells and patient samples revealed a higher expression of Wee1 in EGFRvIII+ cells compared to their EGFRvIII- counterparts. Downregulation of EGFRvIII expression by siRNA resulted in a strong decrease in Wee1 expression. Wee1 inhibition efficiently abrogated radiation-induced G2-arrest and caused radiosensitization, without obvious differences between EGFRvIII- and EGFRvIII+ GBM cells.

CONCLUSION

We conclude that the inhibition of Wee1 is an effective targeting approach for the radiosensitization of both EGFRvIII- and EGFRvIII+ GBM cells and may therefore represent a promising new therapeutic option to increase response to radiotherapy.

A multi-institutional retrospective pooled outcome analysis of molecularly annotated pediatric supratentorial ZFTA-fused ependymoma

Background

ZFTA-RELA (formerly known as c11orf-RELA) fused supratentorial ependymoma (ZFTAfus ST-EPN) has been recognized as a novel entity in the 2016 WHO classification of CNS tumors and further defined in the recent 2021 edition. ZFTAfus ST-EPN was reported to portend poorer prognosis when compared to its counterpart, YAP1 ST-EPN in some previously published series. The aim of this study was to determine the treatment outcome of molecularly confirmed and conventionally treated ZFTAfus ST-EPN patients treated in multiple institutions.

Methods

We conducted a retrospective analysis of all pediatric patients with molecularly confirmed ZFTAfus ST-EPN patients treated in multiple institutions in 5 different countries (Australia, Canada, Germany, Switzerland, and Czechia). Survival outcomes were analyzed and correlated with clinical characteristics and treatment approaches.

Results

A total of 108 patients were collated from multiple institutions in 5 different countries across three continents. We found across the entire cohort that the 5- and 10-year PFS were 65% and 63%, respectively. The 5- and 10-year OS of this cohort of patients were 87% and 73%. The rates of gross total resection (GTR) were high with 84 out of 108 (77.8%) patients achieving GTR. The vast majority of patients also received post-operative radiotherapy, 98 out of 108 (90.7%). Chemotherapy did not appear to provide any survival benefit in our patient cohort.

Conclusion

This is the largest study to date of contemporaneously treated molecularly confirmed ZFTAfus ST-EPN patients which identified markedly improved survival outcomes compared to previously published series. This study also re-emphasizes the importance of maximal surgical resection in achieving optimal outcomes in pediatric patients with supratentorial ependymoma.

Identification of low and very high-risk patients with non-WNT/non-SHH medulloblastoma by improved clinico-molecular stratification of the HIT2000 and I-HIT-MED cohorts

Molecular groups of medulloblastoma (MB) are well established. Novel risk stratification parameters include Group 3/4 (non-WNT/non-SHH) methylation subgroups I-VIII or whole-chromosomal aberration (WCA) phenotypes. This study investigates the integration of clinical and molecular parameters to improve risk stratification of non-WNT/non-SHH MB. Non-WNT/non-SHH MB from the HIT2000 study and the HIT-MED registries were selected based on availability of DNA-methylation profiling data. MYC or MYCN amplification and WCA of chromosomes 7, 8, and 11 were inferred from methylation array-based copy number profiles. In total, 403 non-WNT/non-SHH MB were identified, 346/403 (86%) had a methylation class family Group 3/4 methylation score (classifier v11b6) ≥ 0.9, and 294/346 (73%) were included in the risk stratification modeling based on Group 3 or 4 score (v11b6) ≥ 0.8 and subgroup I-VIII score (mb_g34) ≥ 0.8. Group 3 MB (5y-PFS, survival estimation ± standard deviation: 41.4 ± 4.6%; 5y-OS: 48.8 ± 5.0%) showed poorer survival compared to Group 4 (5y-PFS: 68.2 ± 3.7%; 5y-OS: 84.8 ± 2.8%). Subgroups II (5y-PFS: 27.6 ± 8.2%) and III (5y-PFS: 37.5 ± 7.9%) showed the poorest and subgroup VI (5y-PFS: 76.6 ± 7.9%), VII (5y-PFS: 75.9 ± 7.2%), and VIII (5y-PFS: 66.6 ± 5.8%) the best survival. Multivariate analysis revealed subgroup in combination with WCA phenotype to best predict risk of progression and death. The integration of clinical (age, M and R status) and molecular (MYC/N, subgroup, WCA phenotype) variables identified a low-risk stratum with a 5y-PFS of 94 ± 5.7 and a very high-risk stratum with a 5y-PFS of 29 ± 6.1%. Validation in an international MB cohort confirmed the combined stratification scheme with 82.1 ± 6.0% 5y-PFS in the low and 47.5 ± 4.1% in very high-risk groups, and outperformed the clinical model. These newly identified clinico-molecular low-risk and very high-risk strata, accounting for 6%, and 21% of non-WNT/non-SHH MB patients, respectively, may improve future treatment stratification.

MR Imaging and Clinical Characteristics of Diffuse Glioneuronal Tumor with Oligodendroglioma-like Features and Nuclear Clusters

BACKGROUND AND PURPOSE

Diffuse glioneuronal tumor with oligodendroglioma-like features and nuclear clusters (DGONC) is a new, molecularly defined glioneuronal CNS tumor type. The objective of the present study was to describe MR imaging and clinical characteristics of patients with DGONC.

MATERIALS AND METHODS

Preoperative MR images of 9 patients with DGONC (median age at diagnosis, 9.9 years; range, 4.2-21.8 years) were reviewed.

RESULTS

All tumors were located superficially in the frontal/temporal lobes and sharply delineated, displaying little mass effect. Near the circle of Willis, the tumors encompassed the arteries. All except one demonstrated characteristics of low-to-intermediate aggressiveness with high-to-intermediate T2WI and ADC signals and bone remodeling. Most tumors (n = 7) showed a homogeneous ground-glass aspect on T2-weighted and FLAIR images. On the basis of the original histopathologic diagnosis, 6 patients received postsurgical chemo-/radiotherapy, 2 were irradiated after surgery, and 1 patient underwent tumor resection only. At a median follow-up of 61 months (range, 10-154 months), 6 patients were alive in a first complete remission and 2 with stable disease 10 and 21 months after diagnosis. The only patient with progressive disease was lost to follow-up. Five-year overall and event-free survival was 100% and 86±13%, respectively.

CONCLUSIONS

This case series presents radiomorphologic characteristics highly predictive of DGONC that contrast with the typical aspects of the original histopathologic diagnoses. This presentation underlines the definition of DGONC as a separate entity, from a clinical perspective. Complete resection may be favorable for long-term disease control in patients with DGONC. The efficacy of nonsurgical treatment modalities should be evaluated in larger series.

JS04.4.A Beyond β-catenin: Genetic alterations ofTP53 andOTX2 and older age indicate increased risk of relapse in WNT medulloblastomas

Background

This genetic analysis of WNT-activated medulloblastomas (WNT-MBs) aimed to re-evaluate the prognostic impact of age, TP53 mutations and to identify specific chromosomal aberrations as possible prognostic markers.

Material and Methods

In a cohort of 191 patients with WNT-MBs, mutations in CTNNB1, APC and TP53 were analyzed by Sanger and/or NGS panel sequencing. Chromosomal copy number aberrations were assessed by high-resolution, genome-wide molecular inversion probe technology (MIP), SNP6 array, and/or 850k methylation bead-array hybridization. Association with prognosis was evaluated in 133 patients with follow-up data from the HIT2000 medulloblastoma trial, HIT registries, and the NOA-07 trial.

Results

CTNNB1 mutations were present in 92.2% of the samples. APC mutations were found in 6.8% (13 samples). One CTNNB1 wildtype tumor gained WNT-activation due to a homozygous deletion of FBXW7. Monosomy 6 was present in 78.6%, and more frequent in children compared to adolescents/adults (≥16 years). Adolescents/adults showed worse overall survival (OS; p=0.009) compared to children, but not worse progression-free survival (PFS; p=0.106). With an age cut-off at 18 years, no survival difference was found. Also adolescents alone (16-20 years) had worse OS (p=0.003) compared to children, whereas in patients ≥21 (n=12 adults with PFS/OS data) no tumor progression/relapse occurred. Only one adult died due to therapy-related complications. WNT-MB patients with tumors harboring TP53 mutations (24/133, 18.1%) showed significant worse PFS (p=0.001), which was also found in children and adolescents individually (p=0.004, resp. p=0.017). Gains of the OTX2 locus on chromosome 14q found in 40.2% (35/87) of samples were independent of TP53 mutations and also associated with poor PFS and OS (p=0.034, resp. p=0.016). Individual analyses of OTX2 gains within age groups showed only worse OS in children (p=0.012). Multivariate Cox regression analysis for PFS identified both genetic alterations, but not age, as independent prognostic markers. For OS, multivariate analysis found OTX2 gains and older age as independent prognostic markers.

Conclusion

Our data suggest that adolescent patients with WNT-MB and those patients carrying TP53 mutations or OTX2 gains - independent of age - are at higher risk of relapse. Eligibility of these patients for therapy de-escalation trials needs to be debated.

MEDB-61. Genetic alterations ofTP53 andOTX2 indicate increased risk of relapse in WNT medulloblastomas

PURPOSE: This genetic analysis of WNT-activated medulloblastomas (WNT-MBs) aimed to re-evaluate the prognostic impact of TP53 mutations and to identify specific chromosomal aberrations as possible prognostic markers in a retrospective cohort of patients treated according to the protocols of the HIT medulloblastoma studies. PATIENTS AND METHODS: In a cohort of 191 patients with WNT-MBs, mutations in CTNNB1, APC, and TP53 were analyzed by Sanger and/or NGS panel sequencing. Chromosomal copy number aberrations (CNAs) were assessed by high-resolution, genome-wide molecular inversion probe technology (MIP), SNP6 array, and/or 850k methylation bead-array hybridization. Complete clinical data were available from 120 patients. RESULTS: Patients with WNT-MBs had a female predominance (1.4:1) and a median age of 13 years (range 3-69 years). CTNNB1 mutations were present in 92.2% of the samples, APC mutations in 6.8%. One CTNNB1 wildtype tumor gained WNT-activation due to a homozygous deletion of FBXW7. Monosomy 6 was present in 78.6%, but more frequent in children compared to adults. 16.1% of the tumor samples showed TP53 mutations, of those 60% with nuclear positivity for the p53 protein. A loss of heterozygosity at the TP53 locus on chromosome 17p13.1 was found in 40.7% (11/27) of TP53 mutant tumor samples and in 18.5% of the whole cohort (24/130 cases). Patients with tumors harboring TP53 mutations showed significant worse progression-free survival (PFS; p=0.001), but not overall survival (OS) and were enriched for chromosomes 17p (p=0.001), 10, and 13 losses. Gains of the OTX2 locus on chromosome 14q were also associated with poor PFS and OS (p=0.017 resp. p=0.006). Multivariate Cox regression analysis identified both genetic alterations as independent prognostic markers for PFS and OS. CONCLUSION: For ongoing and future de-escalation trials for patients with WNT medulloblastomas, we recommend to exclude patients with tumors carrying TP53 mutations or OTX2 gains.

RARE-12. Pineoblastoma of children and young adults in a national population: An analysis of the HIT-MED study cohort

BACKGROUND: Pineoblastoma is a malignant tumor of the pineal gland and accounts for <1% of all pediatric brain tumors. PURPOSE/METHODS: Patients <21 years (y) with pineoblastoma confirmed by central neuropathology review between 2001–2021 and included into the HIT2000 trial, HIT2000interim- or I-HIT-MED-registries were eligible. RESULTS: 88 patients were identified. Age at diagnosis was 0.01–20.71y (median 9.34y), median follow-up was 6.54y (IQR 1.78–12.41y) in 48 patients alive at last follow-up. 20 patients were <4y and received chemotherapy with intent to avoid radiotherapy. Of these, 7 patients were alive at last follow-up, two patients were radiotherapy-naïve and 5 patients had undergone CSI + boost (4 after incomplete response and one after progression). 5-y-PFS/OS in 68 patients >4y differed according to metastatic status (M0 (n=40) 72.7±8.3%/75.0±8.3%; M+ (n=28) 28.7±10.3%/40.8±10.9%, p=0.001/0.001). Therapy escalation in M0 patients by giving SKK chemotherapy before radiotherapy did not improve PFS/OS compared to upfront radiotherapy (5-y-PFS/OS 70.7±14.3%/70.0±14.5% vs 74.2±10.1%/78.9±9.4%, p=0.61/0.73). Applied CSI dosages were 24–50Gy (mean 35.6Gy) with no prognostic value of specific dosages being observed. Similarly, in M0 patients hyperfractionated radiotherapy (2x1.0Gy/d, total dose (TD) 36Gy, n=23) was not superior to conventional radiotherapy (1.6Gy/d, TD 35.2Gy, n=7). In all patients, favorable prognostic factors were age >4y (5-y-PFS/OS 54.1±7.0%/60.0±7.0% vs 30.0 ±10.2%/35.0±10.7%, p=0.012/0.053) and radiotherapy in primary therapy (5-y-PFS/OS 55.8±6.5%/61.4±6.4% vs 14.4±9.4%/21.4±11.0%, p<0.001/=0.003), whereas unfavorable prognosis was associated with metastatic disease (5-y-PFS/OS 33.6±9.0%/45.9±9.3% vs 58.8±7.6%/59.3±7.7%, p=0.028/0.086). CONCLUSION: Survival is poor in pineoblastoma patients <4y treated without radiotherapy. Unfavorable prognosis was associated with metastatic disease, especially in older children. Chemotherapy combined with CSI is effective for non-metastatic patients at age >4y. Further research will consider biological subgroups to enhance risk stratification and identify approaches for therapy improvements.

MEDB-16. Persistent radiological lesions at the end of primary therapy in childhood medulloblastoma: residual lesion or active residual tumor?

BACKGROUND: Magnetic resonance imaging (MRI) of patients with medulloblastoma (MB) often shows persistent residual findings after primary treatment. Criteria for characterizing these lesions and consensus on further therapeutic approaches are not established. MATERIAL AND METHODS: Eighty-four patients ≥4 years with centrally reviewed residual lesions on MRI at the end of primary therapy with initial surgery between 2000 and 2018 were identified. Data were extracted from the German HIT-MED database. RESULTS: Median age at initial diagnosis was 9.3 (4.0-20.8) years. 91.7% were histologically classified as CMB, 7.1% as LC/AMB and 1.2% as DMB. The majority (65.5%) of the evaluated cohort was assigned to molecular subgroup 4, 24.1% to group 3, 6.8% to WNT, 3.4% to SHH. Median follow-up for survivors was 5.96 (1.41-16.67) years. Univariate analysis revealed that patients showing an overall partial response (PR) to primary therapy have a significantly lower risk of progression of residual lesions compared to patients with stable disease (SD) (5-year PFS [PR]: 62.5±7,0; 5-year PFS [SD]: 35.9±12.8; 5-year OS [PR]: 85.6±5.1; 5-year OS [SD]: 54.1±13.7; p=0.02 [PFS], p=0.04 [OS]). Additionally, patients with multiple residual lesions (M+ and R+) were at higher risk of progression (5-year PFS [R+ only]: 72.4±12.0, 5-year PFS [R+/M+]: 22.9±17.9; p=0.02 [PFS]). Further procedures after the end of primary therapy (additional resections, chemotherapy, radiotherapy) did not impact on PFS and OS. These results were confirmed by multivariate Cox regression. For molecular or histological type no significant effect was found, presumably due to small cohort. CONCLUSION: PFS in patients with residual lesions at the end of primary treatment depends on the overall response to primary therapy. Additional procedures do not seem to be superior compared to watch-and-wait strategies. Decisions regarding further therapies should be scrutinized on a case-by-case basis. Further identification of biomarkers is warranted.

MEDB-50. Assessment of cellular radiosensitivity and DNA repair in medulloblastoma cell lines and patient-derivded xenograft slice cultures

Medulloblastoma (WHO grade 4) is the most common malignant brain tumor of childhood. Despite the high importance of radiotherapy for disease control, the mechanisms underlying response and resistance to radiotherapy are incompletely understood. Therefore, we assessed the radiosensitivity and DNA repair capacity of medulloblastoma cell lines in-vitro and of patient-derived xenograft (PDX) models ex-vivo. Cell survival after irradiation of seven medulloblastoma cell lines displaying different subgroups was assessed via colony formation assay (DAOY, UW228, UW473, SJMM4, ONS-76, HDMB-03, D283). The ONS-76 and the mouse SJMM4 cell line were the most radioresistant strains (surviving fraction after 6 Gy (SF6): 0.33 and 0.31, respectively), followed by UW473, UW 228 and DAOY cells (SF6 0.16-0.21). The non-WNT/non-SHH-activated cell lines HDMB-03 and D283 cells demonstrated profoundly higher cellular radiosensitivity (SF6 <0.05). Analysis of residual (24h after irradiation) DNA double-strand breaks (DSB) as assessed by co-localized γH2AX/53BP1-foci demonstrated a significant correlation between DSB repair capacity and cellular survival. To use a more reliable pre-clinical model for medulloblastoma, we further examined DNA repair foci in ex-vivo irradiated slice cultures of PDX models MED-113 (SHH) and NCH2194 & HT028 (Gr. 3). Immunofluorescence analyses of frozen sections demonstrated non-hypoxic (pimonidazole-negative) and proliferating (EdU-positive) cells at the outer rim of the tumor slices. Two hours after irradiation all three PDX models showed a strong increase in 53BP1-foci, clearly indicating DNA damage induction. Most radiation-induced DSB were repaired after 24h. In a first radiosensitization approach, we treated the HT028 model with the PARP inhibitor olaparib (1µM ± 2Gy irradiation). Twenty-four hours after treatment the sample displayed a strong increase in the amount and size of 53BP1-foci, indicating compromised DNA repair. Further in-vitro and ex-vivo investigations with the aim to predict individual radiosensitivity and effective radiosensitization strategies are ongoing.

MEDB-38. Significance of CSF cytology and neurologic deterioration in relapsed medulloblastomas in the German HIT-REZ-97/-2005 Studies and the HIT-REZ-Register

BACKGROUND: Follow-up examinations are an essential part of the aftercare of patients with brain tumours. We investigated survival in relation to neurological impairment and positive CSF findings at first relapse/progression of medulloblastomas. METHODS: We collected data from patients with relapsed medulloblastoma from the German HIT-REZ studies (HIT-REZ-1997, HIT-REZ-2005, HIT-REZ-Register, n=342). Survival differences dependent on tumour cell-positive and -negative CSF cytology as well as on new onset or worsening of neurological impairment (i.e. headache, nausea/vomiting, ataxia, seizures and others) were analysed. RESULTS: 247 patients with a recurrent medulloblastoma were evaluable for CSF cytology at first relapse/progression (positive n=97, negative n=150). Patients with tumour cell-positive CSF results showed a significantly shorter median PFS and OS time compared to patients with negative CSF cytology [PFS: 9.1 (CI: 5.3-12.9) vs. 16.8 (CI: 13.8-19.8) months, plog rank test=0.001; OS: 14.4 (CI: 12.3-16.4) vs. 41.8 (CI: 33.3–50.4) months, plog rank test<0.001]. The shortest PFS and OS were observed in SHH-activated (n=18) and group 3 medulloblastomas (n=23) independently of CSF cytology result [median PFSSHH: 4.3 (CI:1.1-12.2), OSSHH: 6.3 (CI:1.1-18.7); PFSgroup3: 4.2 (CI:2.3-13.1), OSgroup3: 13.2 (CI:7.1-18.5) months]. For analysis of the impact of neurological deterioration on survival at first relapse, 249 Patients were evaluable. 105 patients with new or severely worsened neurological impairment at first relapse/progression displayed a significantly poorer PFS and OS time in comparison to 144 patients with unchanged or improved neurological symptoms [PFS: 8.2 (CI: 6.0-10.3) vs. 14.9 (CI: 12.0-17.9) months, plog rank test=0.001; OS: 15.1 (CI: 9.5-20.6) vs. 32.6 (CI: 26.2-38.4) months, plog rank test<0.001]. CONCLUSIONS: Patients with relapsed medulloblastoma show significantly worse survival (PFS and OS) in presence of positive CSF cytology or neurologic deterioration at relapse. These findings could be relevant for patient/parents counselling and treatment recommendations at relapse. Funded by the German Children Cancer Foundation

EPEN-27. Epigenetic dissection of spinal ependymomas (SP-EPN) separates tumors with and withoutNF2 mutation

Ependymomas encompass multiple, clinically relevant tumor types based on localization, genetic alterations, and epigenetic and transcriptomic profiles. Tumors belonging to the methylation class of spinal ependymoma (SP-EPN) represent the most common intramedullary neoplasms in children and adults. However, molecular data of SP-EPN are scarce, and clear treatment recommendations are lacking. The only known recurrent genetic events in SP-EPN are loss of chromosome 22q and NF2 mutations. Yet, it remains unclear whether SP-EPN with germline or sporadic NF2 mutations or with NF2 wild type status differ clinically or molecularly. To provide a comprehensive molecular profile of SP-EPN, we integrated epigenetic, genomic, transcriptomic, and histological analyses of up to 237 cases. Clustering of methylation data revealed two distinct molecular SP-EPN subtypes. The distribution of NF2 mutated cases differed significantly across these subtypes (p <0.0001): The vast majority of tumors harboring either a previously known NF2 germline mutation or a sporadic mutation were assigned to subtypes A, whereas subtype B tumors mainly contained NF2 wild type sequences. In addition, subtype A tumors showed a lower frequency of MGMT promoter methylation (p= 0.018) and contained almost all pediatric patients of the cohort. Whole-exome sequencing (30 cases) identified numerous mutations in NF2 wild type and mutated tumors. Mutated genes in NF2 wild type tumors were enriched for genes associated with cell cycle and cytoskeleton. RNA sequencing revealed two distinct transcriptional groups with upregulation of proliferative genes in one group and upregulation of cilial genes in the other group. The molecular subtypes displayed subtle, but significant differences in the appearance of histopathological characteristics, such as surfaces, inflammation, and hyalinized vessels. Investigation of clinical parameters is ongoing and will complete the picture of SP-EPN heterogeneity as an important basis for future clinical decision-making.

MEDB-04. Young children with metastatic medulloblastoma: frequent requirement for radiotherapy in children with non-WNT/non-SHH medulloblastoma despite highly intensified chemotherapy – Results of the MET-HIT2000-BIS4 trial

PURPOSE: To assess outcomes and biological parameters of children younger than 4 years with metastatic medulloblastoma treated within the MET-HIT2000-BIS4 trial or outside the protocol. PATIENTS AND METHODS: 48 trial participants received either carboplatin/etoposide (years 2001 to 2005, n=18) or an intensified Head-Start-based induction (years 2006 to 2011, n=30), both groups with intraventricular methotrexate, followed by high-dose chemotherapy (HDCT) and/or craniospinal radiotherapy (CSI). In an extended cohort, data of 58 additional were grouped with trial participant data. RESULTS: Trial participants (n=48): After intensified induction, both response (26/27 vs. 10/17 eligible patients, p=0.003), and progression-free survival (PFS, 5-year-PFS (5y-PFS): 57% vs 28%, p=0.014) was higher after intensified induction. However, CSI- /progression-free survival (CSIfPFS) was low (5-year CSIfPFS 17%). Biological subtype influenced 5y-CSIfPFS with 3% in non-WNT/non-SHH medulloblastoma vs. 58% in SHH-medulloblastoma (p<0.001), independent of induction regimens. Extended cohort (n=48 on trial and n=58 off trial): Non-WNT/non-SHH medulloblastoma (n=74, all treated in analogy to the MET-HIT2000-BIS4 protocol): Most frequent subtypes were II (5y-PFS 0%, 5y-OS 7%, n=21) and IV (5y-PFS 55%, 5y-OS 57%, n=16). 5y-CSIfPFS was only 8% [n=5]. Among patients in CR (n=13) or PR (n=10), who received HDCT but not CSI in primary therapy, only 5 were CSI-free survivors (CR: n=4/PR: n=1; Subtype III: n=1, Subtype IV: n=2, non-WNT/non-SHH by histology: n=2). SHH-medulloblastoma (n=32, treated with MET-HIT2000-BIS4 [n=16] or HIT2000-BIS4/HIT-SKK chemotherapy [with intrventricular methotrexate, without HDCT; n=16]): 5y-PFS (72%) and 5y-CSIfPFS (69%) did not differ according to therapy or SHH-subgroups. Two therapy-related deaths occurred on MET-HIT2000-BIS4 therapy. Relapses were more frequent after HIT-SKK (p=0.083). CONCLUSIONS: Despite maximally intensified chemotherapy, patients with metastatic non-WNT/non-SHH medulloblastoma almost always require craniospinal radiotherapy to survive their disease. In SHH-activated medulloblastoma, HDCT might better control the disease but careful vigilance of toxicity is important.

MEDB-14. Clinical outcome of pediatric medulloblastoma patients with Li-Fraumeni syndrome

PURPOSE: The prognosis for SHH-medulloblastoma (MB) patients with Li-Fraumeni syndrome (LFS) is poor. Due to lack of comprehensive data for these patients, it is challenging to establish effective therapeutic recommendations. We here describe the largest retrospective cohort of pediatric LFS SHH-MB patients to date and their clinical outcomes. PATIENTS AND METHODS: N=31 patients with LFS SHH-MB were included in this retrospective multicenter study. TP53 variant type, clinical parameters including treatment modalities, event-free survival (EFS) and overall survival (OS), as well as recurrence patterns and incidence of secondary neoplasms, were evaluated. RESULTS: All LFS-MBs were classified as SHH subgroup, in 30/31 cases based on DNA methylation analysis. The majority of constitutional TP53 variants (72%) represented missense variants, and all except two truncating variants were located within the DNA-binding domain. 54% were large cell anaplastic, 69% gross totally resected and 81% had M0 status. The 2-(y)ear and 5-(y)ear EFS were 26% and 8,8%, respectively, and 2y- and 5y-OS 40% and 12%. Patients who received post-operative radiotherapy (RT) followed by chemotherapy (CT) showed significantly better outcomes (2y-EFS:43%) compared to patients who received CT before RT (30%) (p<0.05). The 2y-EFS and 2y-OS were similar when treated with protocols including high-dose chemotherapy (EFS:22%, OS:44%) compared to patients treated with maintenance-type chemotherapy (EFS:31%, OS:45%). Recurrence occurred in 73.3% of cases independent of resection or M-status, typically within the radiation field (75% of RT-treated patients). Secondary malignancies developed in 12.5% and were cause of death in all affected patients. CONCLUSIONS: Patients with LFS-MBs have a dismal prognosis. This retrospective study suggests that upfront RT may increase EFS, while intensive therapeutic approaches including high-dose chemotherapy did not translate into increased survival of this patient group. To improve outcomes of LFS-MB patients, prospective collection of clinical data and development of treatment guidelines are required.

MEDB-37. Chemotherapy response prediction by molecular risk factors in metastatic childhood medulloblastoma

BACKGROUND: Childhood metastatic medulloblastoma (MB) frequently receive postoperative chemotherapy (CT) before craniospinal irradiation. Some MB show stable (SD) or progressive disease (PD) upon CT. Identification of biomarkers for non-response might allow therapy-modifications. METHODS: Patients registered to the German HIT-MED database (2001–2019) were eligible if they were 4-21 years old at diagnosis of a M2/M3-metastasized MB, received therapy in analogy to the MET-HIT2000-AB4 protocol, had centrally reviewed response assessment after 2 cycles HIT-SKK-CT and DNA-methylation analysis was available. DNA-methylation-based tumor classification and whole chromosomal (WC) losses/gains were derived from DNA-methylation arrays. RESULTS: 51/163 (31.3%) patients (median age: 9.8±4.4 years, median follow-up: 6.2±4.0 years) presented SD/PD during/after HIT-SKK-CT and were classified as non-responder. Response to CT had high predictive value for PFS/OS (5-year PFS responder: 67.9±4.8 %, non-responder: 26.1±6.6%, p&lt;0.01 / 5-year OS responder: 80.0±4.2%, non-responder: 45.9±8.0%, p&lt;0.01). Patients with nonWNT/nonSHH-MB subtype II (response: 7/13), subtype III (response: 6/19) and/or MYC-amplification (n=27, overlap subtype II/III: n=11/8, response: 14/27) were less likely to respond, while all 6 of WNT, 8/9 SHH-TP53-wildtype and 1/1 SHH-TP53-mutant responded (Mann-Whitney-U-test p=0.04). Further, ≥2 WC losses/gains of chromosome 7/8/11 was associated with superior response (n=29/32, others: n=83/131, Mann-Whitney-U-test p&lt;0.01). We identified a very-high-risk-cohort (any two criteria of: &lt;2 WC losses/gains of chromosome 7/8/11, MYC-amplification, MB subtype II, III, V, or VIII, n=94), and a standard-risk-cohort (WNT or any ≥2 WC losses/gains of chromosome 7/8/11, n=37) with 40 vs. 8 % non-response and 44±5/60±5 vs. 79±7/87±6% 5-year PFS/OS (p&lt;0.01/p&lt;0.01), respectively. Non-response in n=32 non-VHR/non-SR-patients was 32% with a 5-years PFS/OS of 60±10/77±8%. CONCLUSION: Molecular information can be helpful to predict response to chemotherapy. Upon validation, this may contribute to improve treatment stratification in metastatic MB.

MEDB-51. Impact of residual tumor on outcomes in children and adolescents with medulloblastoma in the German HIT-cohort

INTRODUCTION: To date, a historical threshold of 1.5cm² extent of resection (EOR) of the primary tumor is used for risk stratification in pediatric medulloblastoma (MB). METHODS: Data of n=348 patients with MB included into the German HIT-MED studies and registries from 2000-2017 were retrospectively analyzed. Kaplan-Meier statistics and Cox regressions were calculated to determine the influence of EOR, histological and molecular subtype, MYC/N-amplification and presence of metastases at first diagnosis on overall and progression-free survival (OS/PFS). ROC curves were calculated aiming at identifying a new EOR cut-off. RESULTS: Median age at diagnosis was 6.8 [0.1-20.5] years. After initial surgery, residual tumor (R) ≥1.5cm² was present in 129/348 patients (37%). 57% presented with additional metastases. In most cases, classic histology was found (71%, DMB/MBEN: 20%, LC/AMB: 9%). Molecular subtype was nonWNT/nonSHH in 68% (Group 4: 37%, Group 3: 31%), WNT in 6% and SHH-activated types in 26% of evaluated cases (n=208). MYC/MYCN-amplification was present in 5 and 4%, respectively. 41/348 patients received additional surgery, resulting in 73% GTR (not reported: n=22). EOR had no significant impact on OS/PFS (GTR: 5y-OS/PFS 69.9±3.4/57.6±3.7%, STR: 5y-OS/PFS 71.4±4.1/56.2±4.5%, p=0.6/0.8; Cox: p=0.2/0.4; median follow-up 8.4 [0.1-18.0] years). ROC curves did not identify a significantly improved limit for outcome-relevant EOR cut-off. Analyses confirmed less favorable OS/PFS for patients with metastatic disease (p=0.04/p<0.05), LC/AMB (p<0.05/p<0.05), Group 3 (p<0.05/p<0.05), and MYC-amplification (p<0.05/p<0.05). Cox regression confirmed an increased risk for Group 3 (OS: HR=4.74, p<0.05, PFS: HR=2.90, p<0.05) and M+ (PFS: HR=2.69, p<0.05). DISCUSSION: No distinct influence of EOR </≥1.5cm² on OS/PFS in pediatric MB was detected. The relevance of EOR and the historical limit of 1.5cm² should be further investigated in distinct MB subtypes and in context of other risk factors.

EPEN-19. Impact of molecular classification on prognosis in children and adolescents with spinal ependymoma: Results from the HIT-MED database

PURPOSE: Ependymomas of the spinal cord are rare among children, and individual risks of disease progression are difficult to predict. This study aims at evaluating the prognostic impact of DNA methylation-based classification in children with spinal ependymoma. METHODS: Eighty-two patients with spinal ependymoma &lt;22 years registered in the HIT-MED database between 1992 and 2021 were included. Clinical, radiological, and histopathological data were collected retrospectively. DNA methylation profiles of 46 tumors were classified according to the Heidelberg Brain Tumor Classifier. RESULTS: Spinal myxopapillary ependymoma (SP-MPE, n=27) was the most common methylation group followed by spinal ependymoma (SP-EPN, n=15). Two cases belonged to MYCN-amplified subgroup, one had no match, and one was re-classified as anaplastic pilocytic astrocytoma (the latter excluded from final analysis). WHO grade I and III ependymomas (according to the WHO 2016 classification) classified predominantly as SP-MPE, whereas grade II ependymomas clustered into SP-MPE and SP-EPN. 6/15 patients with SP-EPN (40%) suffered from Neurofibromatosis type 2. Among patients with SP-MPE, 23 underwent gross-total and four a subtotal resection (GTR/STR). Relapses of SP-MPE were more common following STR (5-year progression-free survival (5y-PFS) [STR] 25.0% [95% confidence interval: 0.0-68.4], [GTR] 75.0% [53.4-96.6], p=0.003). In the SP-EPN group, 2/8 patients relapsed after STR (5y-PFS 64.3% [22,3-100]) and 0/7 after GTR (n.s.). WHO I° ependymoma had significantly inferior PFS than II° and III° ependymoma (5y-PFS [I°] 39.0% [5.8-62.2], [II°] 82.4% [67.8-97.0], [III°] 50.5% [18.9-82.1], p=0.009). However, PFS did not significantly differ between SP-MPE and SP-EPN (5y-PFS 65.9% [44.9-86.9], 76.9% [46.3-100], respectively). CONCLUSION: Spinal ependymomas of WHO grade I go along with relatively poor PFS in our cohort, while DNA methylation profiling does not segregate patients into distinct risk groups. Still, larger cohorts and further investigations of methylation class heterogeneity in pediatric spinal ependymomas are needed to complete the basis for future clinical decision-making.

MEDB-41. Identifying a subgroup of patients with early childhood sonic hedgehog-activated medulloblastoma with unfavorable prognosis after treatment with radiation-sparing regimens including intraventricular methotrexate

PURPOSE/METHODS: Clinical and molecular risk factors in 142 patients <5 years with desmoplastic medulloblastoma (DMB) or medulloblastoma with extensive nodularity (MBEN) were investigated. Patients were diagnosed between 1992 and 2020 and treated with radiation-sparing approaches, 131 with intraventricular methotrexate. 14 patients with metastatic disease received high-dose chemotherapy. DNA methylation profiles of 77 sonic hedgehog (SHH)-activated medulloblastoma were reclassified according to the Heidelberg Brain Tumor Classifier Version 12.3. RESULTS: While metastatic disease or incomplete resection did not impact progression-free survival (PFS) and overall survival (OS), patients with MBEN had superior outcomes to DMB (5-year PFS 93% vs 71%, p=0.004; 5-year OS 100% vs 90%, p=0.026). Older patients had less favorable PFS (5-year PFS [>3 years] 47% vs 85% [<1 year] vs 84% [1-3 years], p<0.001). No TP53 mutations were detected (n=47). DNA methylation classification identified three subgroups: SHH-1_v12.3 (n=39), SHH-2_v12.3 (n=19), and SHH-3_v12.3 (n=19), with distinct cytogenetic profiles (chromosome 2 gains in SHH-1_v12.3, very few alterations in SHH-2_v12.3, and chromosome 9q losses in SHH-3_v12.3), age profiles (median age [years] SHH-1_v12.3: 1.7, SHH-2_v12.3: 0.9, SHH-3_v12.3: 3.0, p<0.001), and histological distribution (SHH-2_v12.3: 74% MBEN, SHH-1_v12.3/SHH-3_v12.3: 77%/79% DMB, p<0.001). PFS was more unfavorable in patients with SHH-3_v12.3-medulloblastoma (5-year PFS 53% vs 86% [SHH-1_v12.3] vs 95% [SHH-2_v12.3], p=0.002), which remained the only risk factor on multivariable Cox regression for PFS. OS was comparable (5-year OS 94% [SHH-3_v12.3] vs 97% [SHH-1_v12.3] vs 100% [SHH-2_v12.3], p=0.6). 8/9 patients with SHH-3_v12.3-medulloblastoma received radiotherapy at relapse (6 craniospinal, 2 local [1 Gorlin syndrome, 1 BRCA2 germline mutation], 1 no radiotherapy [Gorlin syndrome]). CONCLUSION: We identify patients with an increased risk of relapse when treated with radiation-sparing approaches among children with early childhood SHH-medulloblastoma. If these tumors differ from SHH-3-medulloblastoma typically described in older children remains to be verified. Treatment recommendations need to consider cancer predisposition syndromes.

EPEN-06. Comprehensive profiling of myxopapillary ependymomas identifies a distinct molecular subtype with relapsing disease

Myxopapillary ependymoma (MPE) is a heterogeneous disease regarding histopathology and outcome. The underlying molecular biology is poorly understood, and markers that reliably predict the patients’ clinical course are unknown. We assembled a cohort of 185 tumors classified as MPE based on DNA methylation from pediatric, adolescent, and adult patients. Methylation patterns, copy number profiles, and MGMT promoter methylation were analyzed for all tumors, 106 tumors were evaluated histomorphologically, and RNA sequencing was performed for 37 cases. Based on methylation profiling, we defined two subtypes MPE-A and MPEB, and explored associations with epidemiological, clinical, pathological, and molecular characteristics of these tumors. Tumors in the methylation class MPE were histologically diagnosed as WHO grade I (59%), WHO grade II (37%), or WHO grade III tumors (4%). 75/77 analyzed tumors expressed HOXB13, which is a diagnostic feature not detected in other spinal ependymal tumors. Based on DNA methylation, our series split into two subtypes. MPE-A occurred in younger patients (median age 27 vs. 45 years, p=7.3e-05). They were enriched with WHO grade I tumors and associated with papillary morphology and MGMT promoter hypermethylation (all p&lt;0.001). MPE-B included most tumors initially diagnosed as WHO grade II and cases with tanycytic morphology. Copy number alterations were more common in MPE-A. RNA sequencing revealed an enrichment for extracellular matrix and immune system-related signatures in MPE-A. 15/30 MPE-A could not be totally resected compared to 1/58 MPE-B (p=6.3e-08), and progression-free survival was significantly better for MPE-B (p=3.4e-06, 10-year relapse rate 33% vs. 85%). We unraveled the morphological and clinical heterogeneity of MPE by identifying two molecularly distinct subtypes. These subtypes significantly differed in progression-free survival and will likely need different protocols for surveillance and treatment.

QOL-10. Treatment-induced leukoencephalopathy in pediatric medulloblastoma survivors and its impact on long-term neurocognitive functioning

OBJECTIVES: Leukoencephalopathy (LEP, i.e. white matter T2-/FLAIR-hyperintensities on MRI) and impaired neuropsychological outcome are side effects of multimodal therapy of medulloblastoma. We identified risk factors for LEP and correlated LEP with neurocognitive functioning. PATIENTS AND METHODS: Severity of LEP either at the end of therapy (n=118), two years (n=126), or five years after surgery (n=139) was evaluated according to an adapted Fazekas classification for 162 survivors of medulloblastoma (median age: 7.4 years [range:0.67-19.8 years]). Severity of LEP two or five years after surgery was correlated with treatment and neurocognitive functioning ≥ five years after diagnosis using univariate analyses and multivariate generalized mixed linear models. RESULTS: Two and five years after surgery, incidences of mild/moderate/severe LEP were 21.4%/17.5%/9.5%, and 24.5%/23.7%/8.6%, respectively. Data on severity of LEP both at the end of therapy and five years after surgery was available for 103 patients: LEP grades increased for 1/2 degrees in 18/4 patients and decreased in 13/1 patients, respectively. Both treatment approaches - HIT-SKK chemotherapy including intraventricular methotrexate (SKK) and craniospinal irradiation (CSI) - were associated with increased severity of LEP (CSI+SKK &gt; SKK only &gt; CSI only; p&lt;0.001). Severe LEP only occurred in patients treated with both CSI and SKK. In total 19% of all patients treated with this combination developed severe LEP. Severe LEP correlated with impaired fluid (p=0.013) and crystalline (p=0.012) intelligence and short-term memory (p=0.024) on both univariate level and in multivariate mixed linear models. Among patients treated with CSI doses &gt;30Gy, severe LEP, but not SKK including intraventricular MTX, correlated with impaired neurocognitive functioning. CONCLUSION: After therapy strong changes in LEP rarely occurred. Severe LEP was associated both with the combination of SKK and CSI, and impaired neurocognitive functioning. Further research will be needed to weigh potential benefits of SKK including intraventricular methotrexate with CSI against its neurotoxicity.

MEDB-17. Re-irradiation for recurrent medulloblastoma in a matched cohort: Advantageous especially in patients without resection

INTRODUCTION: Radiotherapy with craniospinal irradiation (CSI) is an important part of initial treatment for medulloblastoma in most children. Radiotherapy after recurrence is currently not widely used. This analysis aims to evaluate whether re-irradiation (RT2) may show survival benefits. METHODS: Data for patients with recurrent medulloblastomas from the German HIT-REZ studies was gathered. Patients with RT2 at 1st recurrence were matched by propensity score to an equal number of patients without radiotherapy. Matching variables were sex, initial therapy, time to recurrence, metastatic stage and therapy at 1st recurrence and radiotherapy at subsequent recurrences. The matched cohort was analysed regarding PFS and OS after 1st recurrence. RESULTS: From a cohort of 240 pre-irradiated patients, 106 patients were matched. Patients with RT2 showed improved median PFS [21.0 months (95%-CI: 17.5 – 27.6)] and OS [37.5 months (CI: 30.0 – 59.4)] compared to control patients [(PFS: 12.0 months (CI: 8.1 – 17.7) / OS: 20.1 months (CI: 14.5 – 44.8)]. When stratifying by resection at recurrence (36.8% resected), a survival advantage for RT2 was found in patients without resection in PFS [19.6 (CI: 14.9 – 31.5) vs. 8.0 months (CI: 5.4 – 14.4)] and OS [41.9 (CI: 30.0 – 59.4) vs. 13.3 months (CI: 8.1 – 36.7)]. However, no advantage was found after resection [PFS: 22.5 (CI: 17.5 – 50.4) vs. 19.1 months (CI: 14.1 – 34.3) / OS: 32.3 (CI: 27.6 – NA) vs. 48 months (CI: 23.4 – NA)]. CSI was used in 6 patients without differences in survival to focal RT2. Median PFS after first irradiation was 32.5 months, after RT2 20.9 months. No patients with RT2 were alive past 10 years after 1st recurrence.CONCLUSION: Patients with recurrent medulloblastoma show benefits from RT2 in median PFS and OS. However, no advantage for RT2 was found when resection was also applied at recurrence. Cure after treatment with RT2 was not found in our cohort.

QOL-04. Histology, treatment, and extent of pretreatment hydrocephalus are major determents of neurocognitive outcome for survivors of pediatric posterior fossa tumors - report from the German HIT-studies

BACKGROUND: Cognitive impairments following pediatric brain tumors are generally attributed to tumor site, surgical intervention, complications as well as to nonsurgical treatment. We investigated impairments for patients with medulloblastoma (MB), ependymoma (EP) and low-grade glioma (LGG) of the cerebellum treated within the German pediatric brain tumor network to compare and rank major determents. PATIENTS+METHODS: Following protocol treatment, 245 patients with MB (n=106), EP (n=32), and cerebellar LGG (n=107, surgery only) were examined 2 + 5 years after diagnosis using the German “Neuropsychological-Basic-Diagnostic” (NBD) tool based on the Cattell-Horn-Carroll model for intelligence. Within this retrospective study, multiple linear regression models were applied. RESULTS: The MB+EP vs. LGG-cohort differed slightly in median age at diagnosis (8.7/6.1 years) and location (cerebellar hemispheres: 8%MB+EP/49.5%LGG), while sex-ratio, grade of resection, extent of pre-operative hydrocephalus were comparable. With smaller median tumor-volume in the MB+EP vs. LGG-cohort (34.1/44.1cm3), ranges broadly overlapped. Median scores of age-appropriate tests were in the lower normal range for all patients for fluid and crystallized intelligence, selective attention, visual-spatial processing (VSP) and verbal short-term memory (median=93-103), but distinctly below for processing speed (PS), and psychomotor speed abilities (PMS) (median=65-84). Higher doses of craniospinal irradiation (>23.4Gy/23.4Gy) resulted in lower scores for most domains for MB-patients compared to LGG-patients (e.g., PS-estimate: >23.4Gy:-27.71, p=0.026/23.4Gy:-9.93, p=0.286). EP-patients (surgery+54Gy local radiation) scored better than LGG-patients except for PS (estimate:-15.65, p=0.111). Impairments were accentuated with higher degrees of hydrocephalus (estimate:-7.64, p=0.103) in patients with incomplete resection (estimate:12.23, p=0.006) for PMS both hands. CONCLUSION: Following age-adapted comprehensive treatment, survivors of a cerebellar tumor show significant impairments of PMS abilities in our trials. Our data suggest that slow growing LGG impair neurocognitive development more than local radiotherapy for ependymoma, while craniospinal irradiation compromises VSP and PS in MB. Initial symptomatic intracranial pressure remains a strong predictor for general neuropsychological impairment.

Comprehensive profiling of myxopapillary ependymomas identifies a distinct molecular subtype with relapsing disease

BACKGROUND

Myxopapillary ependymoma (MPE) is a heterogeneous disease regarding histopathology and outcome. The underlying molecular biology is poorly understood, and markers that reliably predict the patients' clinical course are unknown.

METHODS

We assembled a cohort of 185 tumors classified as MPE based on DNA methylation. Methylation patterns, copy number profiles, and MGMT promoter methylation were analyzed for all tumors, 106 tumors were evaluated histomorphologically, and RNA sequencing was performed for 37 cases. Based on methylation profiling, we defined two subtypes MPE-A and MPEB, and explored associations with epidemiological, clinical, pathological, and molecular characteristics of these tumors.

RESULTS

MPE-A occurred at a median age of 27 years and were enriched with tumors demonstrating papillary morphology and MGMT promoter hypermethylation. Half of these tumors could not be totally resected, and 85% relapsed within 10 years. Copy number alterations were more common in MPE-A. RNA sequencing revealed an enrichment for extracellular matrix and immune system-related signatures in MPE-A. MPE-B occurred at a median age of 45 years and included many tumors with a histological diagnosis of WHO grade II and tanycytic morphology. Patients within this subtype had a significantly better outcome with a relapse rate of 33% in 10 years (p=3.4e-06).

CONCLUSIONS

We unraveled the morphological and clinical heterogeneity of MPE by identifying two molecularly distinct subtypes. These subtypes significantly differed in progression-free survival and will likely need different protocols for surveillance and treatment.

Clinical and molecular characterization of isolated M1 disease in pediatric medulloblastoma: experience from the German HIT-MED studies

Purpose

To evaluate the clinical impact of isolated spread of medulloblastoma cells into cerebrospinal fluid without additional macroscopic metastases (M1-only).

Methods

The HIT-MED database was searched for pediatric patients with M1-only medulloblastoma diagnosed from 2000 to 2019. Corresponding clinical and molecular data was evaluated. Treatment was stratified by age and changed over time for older patients.

Results

70 patients with centrally reviewed M1-only disease were identified. Clinical data was available for all and molecular data for 45/70 cases. 91% were non-WNT/non-SHH medulloblastoma (Grp3/4).

5-year PFS for 52 patients ≥ 4 years was 59.4 (± 7.1) %, receiving either upfront craniospinal irradiation (CSI) or SKK-sandwich chemotherapy (CT). Outcomes did not differ between these strategies (5-year PFS: CSI 61.7 ± 9.9%, SKK-CT 56.7 ± 6.1%). For patients < 4 years (n = 18), 5-year PFS was 50.0 (± 13.2) %. M1-persistence occurred exclusively using postoperative CT and was a strong negative predictive factor (p_PFS/OS < 0.01).

Patients with additional clinical or molecular high-risk (HR) characteristics had worse outcomes (5-year PFS 42.7 ± 10.6% vs. 64.0 ± 7.0%, p = 0.03). In n = 22 patients ≥ 4 years with full molecular information and without additional HR characteristics, risk classification by molecular subtyping had an effect on 5-year PFS (HR 16.7 ± 15.2%, SR 77.8 ± 13.9%; p = 0.01).

Conclusions

Our results confirm that M1-only is a high-risk condition, and further underline the importance of CSF staging. Specific risk stratification of affected patients needs attention in future discussions for trials and treatment recommendations. Future patients without contraindications may benefit from upfront CSI by sparing risks related to higher cumulative CT applied in sandwich regimen.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11060-021-03913-5.

Refining M1 stage in medulloblastoma: criteria for cerebrospinal fluid cytology and implications for improved risk stratification from the HIT-2000 trial

BACKGROUND

Medulloblastoma is the most common malignant paediatric brain tumour, and cerebrospinal fluid (CSF) dissemination (M1 stage) is a high-risk prognostic factor. Criteria for CSF evaluation and for differentiating M0 from M1 stage are not clearly defined, and the prognostic significance of M1 stage in this context is unknown.

PATIENTS AND METHODS

CSF investigations from 405 patients with medulloblastoma of the prospective multicenter trial HIT-2000 (HIirnTumor-2000) were reviewed. Data from 213 patients aged ≥4 years were related to 5-year progression-free (5y-PFS) and overall survival.

RESULTS

Patients with cytological tumour dissemination only (M1 stage only) aged ≥4 years (n = 18) and patients with radiologically detected metastases (M2/3, n = 85) showed a worse 5y-PFS than M0 patients (n = 110) without signs of metastatic disease (5y-PFS 61.1% and 59.6% vs 80.7%; p < 0.02 and p < 0.01, log rank). Patients with positive samples drawn early after surgery who turned negative within 14 days postoperatively (n = 9) and patients with atypical cells (n = 6) showed a 5y-PFS similar to M0 patients. No tumour cells were detected in samples containing <10 nucleated cells. Analysis of cytological criteria showed a better predictive value for tumour cell clusters than ≥2 individual tumour cells.

CONCLUSION

Based on our results, we suggest that CSF medulloblastoma staging should be performed 14 days postoperatively by lumbar puncture, and specimens should contain at least 10 nucleated cells. Cytological tumour dissemination alone (M1 stage only) appears a high-risk prognostic factor associated with an outcome comparable to M2/M3 stage. Tumour cell clusters seem to have a greater impact on prognosis than single tumour cells. This should be validated further.

Gene expression profiling of Group 3 medulloblastomas defines a clinically tractable stratification based on KIRREL2 expression

Medulloblastomas (MB) molecularly designated as Group 3 (Grp 3) MB represent a more clinically aggressive tumor variant which, as a group, displays heterogeneous molecular characteristics and disease outcomes. Reliable risk stratification of Grp 3 MB would allow for appropriate assignment of patients to aggressive treatment protocols and, vice versa, for sparing adverse effects of high-dose radio-chemotherapy in patients with standard or low-risk tumors. Here we performed RNA-based analysis on an international cohort of 179 molecularly designated Grp 3 MB treated with HIT protocols. We analyzed the clinical significance of differentially expressed genes, thereby developing optimal prognostic subdivision of this MB molecular group. We compared the transcriptome profiles of two Grp 3 MB subsets with various outcomes (76 died within the first 60 months vs. 103 survived this period) and identified 224 differentially expressed genes (DEG) between these two clinical groups (Limma R algorithm, adjusted p-value < 0.05). We selected the top six DEG overexpressed in the unfavorable cohort for further survival analysis and found that expression of all six genes strongly correlated with poor outcomes. However, only high expression of KIRREL2 was identified as an independent molecular prognostic indicator of poor patients' survival. Based on clinical and molecular patterns, four risk categories were outlined for Grp 3 MB patients: i. low-risk: M0-1/MYC non-amplified/KIRREL2 low (n = 48; 5-year OS-95%); ii. standard-risk: M0-1/MYC non-amplified/KIRREL2 high or M2-3/MYC non-amplified/KIRREL2 low (n = 65; 5-year OS-70%); iii. high-risk: M2-3/MYC non-amplified/KIRREL2 high (n = 36; 5-year OS-30%); iv. very high risk-all MYC amplified tumors (n = 30; 5-year OS-0%). Cross-validated survival models incorporating KIRREL2 expression with clinical features allowed for the reclassification of up to 50% of Grp 3 MB patients into a more appropriate risk category. Finally, KIRREL2 immunopositivity was also identified as a predictive indicator of Grp 3 MB poor survival, thus suggesting its application as a possible prognostic marker in routine clinical settings. Our results indicate that integration of KIRREL2 expression in risk stratification models may improve Grp 3 MB outcome prediction. Therefore, simple gene and/or protein expression analyses for this molecular marker could be easily adopted for Grp 3 MB prognostication and may help in assigning patients to optimal therapeutic approaches in prospective clinical trials.

Defining the Spectrum, Treatment and Outcome of Patients With Genetically Confirmed Gorlin Syndrome From the HIT-MED Cohort

Gorlin syndrome is a genetic condition associated with the occurrence of SHH activated medulloblastoma, basal cell carcinoma, macrocephaly and other congenital anomalies. It is caused by heterozygous pathogenic variants in PTCH1 or SUFU. In this study we included 16 patients from the HIT2000, HIT2000interim, I-HIT-MED, observation registry and older registries such as HIT-SKK87, HIT-SKK92 (1987 – 2020) with genetically confirmed Gorlin syndrome, harboring 10 PTCH1 and 6 SUFU mutations. Nine patients presented with desmoplastic medulloblastomas (DMB), 6 with medulloblastomas with extensive nodularity (MBEN) and one patient with classic medulloblastoma (CMB); all tumors affected the cerebellum, vermis or the fourth ventricle. SHH activation was present in all investigated tumors (14/16); DNA methylation analysis (when available) classified 3 tumors as iSHH-I and 4 tumors as iSHH-II. Age at diagnosis ranged from 0.65 to 3.41 years. All but one patient received chemotherapy according to the HIT-SKK protocol. Ten patients were in complete remission after completion of primary therapy; four subsequently presented with PD. No patient received radiotherapy during initial treatment. Five patients acquired additional neoplasms, namely basal cell carcinomas, odontogenic tumors, ovarian fibromas and meningioma. Developmental delay was documented in 5/16 patients. Overall survival (OS) and progression-free survival (PFS) between patients with PTCH1 or SUFU mutations did not differ statistically (10y-OS 90% vs. 100%, p=0.414; 5y-PFS 88.9% ± 10.5% vs. 41.7% ± 22.2%, p=0.139). Comparing the Gorlin patients to all young, SHH activated MBs in the registries (10y-OS 93.3% ± 6.4% vs. 92.5% ± 3.3%, p=0.738; 10y-PFS 64.9%+-16.7% vs. 83.8%+-4.5%, p=0.228) as well as comparing Gorlin M0 SKK-treated patients to all young, SHH activated, M0, SKK-treated MBs in the HIT-MED database did not reveal significantly different clinical outcomes (10y-OS 88.9% ± 10.5% vs. 88% ± 4%, p=0.812; 5y-PFS 87.5% ± 11.7% vs. 77.7% ± 5.1%, p=0.746). Gorlin syndrome should be considered in young children with SHH activated medulloblastoma, especially DMB and MBEN but cannot be ruled out for CMB. Survival did not differ to patients with SHH-activated medulloblastoma with unknown germline status or between PTCH1 and SUFU mutated patients. Additional neoplasms, especially basal cell carcinomas, need to be expected and screened for. Genetic counselling should be provided for families with young medulloblastoma patients with SHH activation.

SIOP PNET5 MB Trial: History and Concept of a Molecularly Stratified Clinical Trial of Risk-Adapted Therapies for Standard-Risk Medulloblastoma

BACKGROUND

SIOP PNET5 MB was initiated in 2014 as the first European trial using clinical, histological, and molecular parameters to stratify treatments for children and adolescents with standard-risk medulloblastoma.

METHODS

Stratification by upfront assessment of molecular parameters requires the timely submission of adequate tumour tissue. In the standard-risk phase-III cohort, defined by the absence of high-risk criteria (M0, R0), pathological (non-LCA), and molecular biomarkers (MYCN amplification in SHH-MB or MYC amplification), a randomized intensification by carboplatin concomitant with radiotherapy is investigated. In the LR stratum for localized WNT-activated medulloblastoma and age <16 years, a reduction of craniospinal radiotherapy dose to 18 Gy and a reduced maintenance chemotherapy are investigated. Two additional strata (WNT-HR, SHH-TP53) were implemented during the trial.

RESULTS

SIOP PNET5 MB is actively recruiting. The availability of adequate tumour tissue for upfront real-time biological assessments to assess inclusion criteria has proven feasible.

CONCLUSION

SIOP PNET5 MB has demonstrated that implementation of biological parameters for stratification is feasible in a prospective multicentre setting, and may improve risk-adapted treatment. Comprehensive research studies may allow assessment of additional parameters, e.g., novel medulloblastoma subtypes, and identification and validation of biomarkers for the further refinement of risk-adapted treatment in the future.

PATH-34. MOLECULAR AND CLINICAL HETEROGENEITY WITHIN SPINAL EPENDYMOMAS

Ependymomas encompass multiple clinically relevant tumor types based on localization, genetic alterations, as well as epigenetic and transcriptomic profiles. Distinct global DNA methylation signatures serve as the most powerful diagnostic tool to distinguish these types. The methylation class of spinal ependymomas (SP-EPN) comprises mostly WHO°II tumors with slow progression and incomplete surgical resection rate. Molecular data of SP-EPN are scarce and clear treatment recommendations are lacking although these neoplasms represent the most common intramedullary tumors in children and adults. The only known recurrent genetic events in SP-EPN are the loss of chromosome 22q and mutations of the NF2 gene. However, data on the frequency of NF2 mutations range from 16 % to 71 % and originate from small series that lack epigenetic or transcriptomic characterization. Furthermore, it remains unclear whether SP-EPN with germline or sporadic NF2 mutation or with NF2 wild type status display clinical and other molecular differences. Finally, the underlying genomic and transcriptomic changes of SP-EPN without NF2 mutations are fully unclear. To provide a comprehensive molecular profile of SP-EPN, we integrated genomic and epigenetic analyses and clinical data of 170 cases. Unsupervised hierarchical clustering and t-SNE analyses of methylation data revealed three distinct molecular SP-EPN subtypes. Of the three subtypes, only subtype 1 and subtype 2 contained tumors with NF2 mutations, either as previously known germline mutations or as sporadic mutations without evidence for a syndromic disease (p&lt; 0.0001). Besides the lack of NF2 mutations, subtype 3 tumors showed a higher frequency of MGMT promoter methylation (p= 0.0015) and occurred in significantly older patients compared to tumors of subtypes 1 and 2 (p= 0.0038). Further investigations such as whole-exome sequencing, copy number variation profiling, gene expression analysis, and histological evaluation are ongoing and will add to the picture of molecular and clinical heterogeneity within SP-EPN.

Primary central nervous system sarcoma with DICER1 mutation-treatment results of a novel molecular entity in pediatric Peruvian patients

BACKGROUND

A high frequency of primary central nervous system (CNS) sarcomas was observed in Peru. This article describes the clinical characteristics, biological characteristics, and outcome of 70 pediatric patients.

METHODS

Data from 70 pediatric patients with primary CNS sarcomas diagnosed between January 2005 and June 2018 were analyzed. DNA methylation profiling from 28 tumors and gene panel sequencing from 27 tumors were available.

RESULTS

The median age of the patients was 6 years (range, 2-17.5 years), and 66 of 70 patients had supratentorial tumors. DNA methylation profiling classified 28 of 28 tumors as primary CNS sarcoma, DICER1 mutant. DICER1 mutations were found in 26 of 27 cases, TP53 mutations were found in 22 of 27 cases, and RAS-pathway gene mutations (NF1, KRAS, and NRAS) were found in 19 of 27 tumors, all of which were somatic (germline control available in 19 cases). The estimated incidence in Peru was 0.19 cases per 100,000 children (<18 years old) per year, which is significantly higher than the estimated incidence in Germany (0.007 cases per 100,000 children [<18 years] per year; P < .001). Patients with nonmetastatic disease (n = 46) that were treated with a combination therapy had a 2-year progression-free survival (PFS) rate of 58% (95% CI, 44%-76%) and a 2-year overall survival rate of 71% (95% CI, 57%-87%). PFS was the highest in patients treated with chemotherapy with ifosfamide, carboplatin, and etoposide (ICE) after upfront surgery followed by radiotherapy and ICE (2-year PFS, 79% [59%-100%], n = 18).

CONCLUSIONS

Primary CNS sarcoma with DICER1 mutation has an aggressive clinical course. A combination of surgery, chemotherapy, and radiotherapy seems beneficial. An underlying cancer predisposition syndrome explaining the increased incidence in Peruvian patients has not been identified so far.

LAY SUMMARY

A high incidence of primary pediatric central nervous system sarcomas in the Peruvian population is described. Using sequencing technologies and DNA methylation profiling, it is confirmed that these tumors molecularly belong to the recently proposed entity "primary central nervous system sarcomas, DICER1 mutant." Unexpectedly, DICER1 mutations as well as all other defining tumor mutations (TP53 mutations and RAS-pathway mutations) were not inherited in all 19 patients where analyzation was possible. These tumors have an aggressive clinical course. Multimodal combination therapy based on surgery, ifosfamide, carboplatin, and etoposide chemotherapy, and local radiotherapy leads to superior outcomes.

Chemotherapy strategies for young children newly diagnosed with desmoplastic/extensive nodular medulloblastoma up to the era of molecular profiling – a comparative outcomes analysis of prospective multi-center European and North American trials

Aims

Survival has been poor in several multi-center/national trials since the 1980s, either delaying, avoiding or minimizing brain irradiation in young children with medulloblastoma. The introduction of German regimens supplementing “standard” chemotherapy with both intravenous high-dose (HD-MTX) and intraventricular (IVENT-MTX) methotrexate, and North American regimens incorporating marrow-ablative chemotherapy with autologous hematopoietic cell rescue (HDCx+AuHCR), have reported encouraging outcomes. We performed a comparative outcomes analysis of these differing strategies for young children with desmoplastic/extensive nodular medulloblastoma.

Method

Data from 12 trials reported between 2005 and 2020 for children &lt;six-years-old with desmoplastic/extensive nodular medulloblastoma were reviewed; event-free (EFS) survival+/-standard errors were compared.

Results

The German HIT-SKK’92 and HIT-SKK’00 trials incorporating HD-MTX and IVENT-MTX reported 85+/-8% and 95+/-5% 5-10-year EFS respectively; a third trial (ACNS1221) incorporating HIT-SKK therapy but without IVENT-MTX reported only 49+/-10% EFS. Three trials (Head Start I and II combined and CCG-99703) employing induction chemotherapy without HD-MTX, followed by one or three HDCx+AuHCR cycles, reported 3-5-year EFS of 67+/-16% and 79+/-11%. Two trials employing HD-MTX-containing induction chemotherapy (Head Start III and ACNS0334), followed by one or three HDCx+AuHCR cycles, reported 3-5-year EFS of 89+/-6% and 100%, respectively. Finally, four trials utilizing neither IVENT-MTX nor HDCx+AuHCR (UK-CNS-9204, CCG-9921, COG-P9934 and SJYC07) reported 2-5 year EFS of 35+/-11%, 77+/-9%, 58+/-8% and 53+/-9% respectively.

Conclusion

A trend towards better EFS for young children with desmoplastic/extensive nodular medulloblastoma is observed in trials including eitherHD-MTX and IVENT-MTX or including HD-MTX-containing induction chemotherapy and HDCx+AuHCR. Trials excluding HD-MTX, IVENT-MTX and HDCx+AuHCR have poorer outcomes.

Follow-up evaluation of a web-based pediatric brain tumor board in Latin America

BACKGROUND

Since 2013, pediatric oncologists from Central and South America discuss neuro-oncology cases with experts from North America and Europe in a web-based "Latin American Tumor Board" (LATB). Here, we evaluate the feasibility of recommendations rendered by the Board.

METHODS

An electronic questionnaire was distributed to physicians who had received recommendations between October 2017 and October 2018. Physicians were asked regarding the feasibility of each recommendation given during the LATB discussion. Baseline case characteristics of all presented cases were obtained from anonymized minutes.

RESULTS

Of the 142 patients discussed, data on 103 patients from 15 countries were available, corresponding to 283 recommendations. Physicians followed 60% of diagnostic procedural recommendations and 69% of therapeutic recommendations. The most difficult recommendations to follow were genetic and molecular testing, pathology review, chemotherapy, surgery, and molecular targeted therapies. Histological diagnoses changed in eight of 18 cases in which a pathology review was undertaken. Fifty-four percent of the recommendations that could not be implemented were considered not feasible in the specific context of the patient, while 31% were not implemented due to a decision of the medical staff or the parents (15% not specified). However, 96% of respondents considered the recommendations useful.

CONCLUSION

Recommendations were frequently perceived as useful, and were applicable in the participating institutions. Nevertheless, limitations in availability of diagnostic procedures and treatment modalities affected the feasibility of some recommendations. Tele-oncology tumor boards offer physicians from low- and middle-income countries access to real-time, high-level subspecialist expertise and provide a valuable platform for worldwide information exchange.

Types of deviation and review criteria in pretreatment central quality control of tumor bed boost in medulloblastoma-an analysis of the German Radiotherapy Quality Control Panel in the SIOP PNET5 MB trial

Purpose

In Germany, Austria, and Switzerland, pretreatment radiotherapy quality control (RT-QC) for tumor bed boost (TB) in non-metastatic medulloblastoma (MB) was not mandatory but was recommended for patients enrolled in the SIOP PNET5 MB trial between 2014 and 2018. This individual case review (ICR) analysis aimed to evaluate types of deviations in the initial plan proposals and develop uniform review criteria for TB boost.

Patients and methods

A total of 78 patients were registered in this trial, of whom a subgroup of 65 patients were available for evaluation of the TB treatment plans. Dose uniformity was evaluated according to the definitions of the protocol. Additional RT-QC criteria for standardized review of target contours were elaborated and data evaluated accordingly.

Results

Of 65 initial TB plan proposals, 27 (41.5%) revealed deviations of target volume delineation. Deviations according to the dose uniformity criteria were present in 14 (21.5%) TB plans. In 25 (38.5%) cases a modification of the RT plan was recommended. Rejection of the TB plans was rather related to unacceptable target volume delineation than to insufficient dose uniformity.

Conclusion

In this analysis of pretreatment RT-QC, protocol deviations were present in a high proportion of initial TB plan proposals. These findings emphasize the importance of pretreatment RT-QC in clinical trials for MB. Based on these data, a proposal for RT-QC criteria for tumor bed boost in non-metastatic MB was developed.

Supplementary Information

The online version of this article (10.1007/s00066-021-01822-0) contains supplementary material, which is available to authorized users.

Detailed Clinical and Histopathological Description of 8 Cases of Molecularly Defined CNS Neuroblastomas

Central nervous system neuroblastoma with FOXR2 activation (CNS NB FOXR2) has recently been described as a class of brain tumors sharing common genetic events and a highly similar DNA methylation profile. Most of these tumors have previously been diagnosed as primitive neuroectodermal tumor (PNET). Whereas the entity of PNET has been removed from the WHO classification of brain tumors in its current edition, CNS neuroblastoma was kept as an entity, but still lacks any molecular detail. Here, we describe 8 cases of CNS NB FOXR2 focusing on histomorphological and immunohistochemical features and include magnetic resonance imaging (MRI) for 2 of these cases. MRI revealed large supratentorial masses in superficial location with prominent cysts and necrosis, but little edema. Diffusion and enhancement characteristics were variable. Histological analyses showed that most of the cases displayed neuronal differentiation with necrosis, endothelial proliferation, and high vascularity. Immunohistochemistry revealed strong expression of synaptophysin, MAP2, and OLIG2 as well as moderate proliferation. These findings suggest that tumors with the molecular diagnosis of CNS NB FOXR2 may fit well into the WHO entity of CNS neuroblastoma. Our findings may be helpful when establishing an integrated diagnosis and may be indispensable if molecular data are unavailable.