bluuebunny/crossref_metadata_2025 huggingface dataset:
MEDB-11. MYC overexpression and SMARCA4 loss in cerebellar granule cell precursors cooperate to drive medulloblastoma formation in mice
Authors: Göbel Carolin , Holdhof Dörthe , Schoof Melanie , Kresbach Catena , Schüller Ulrich
Published: June 2022

Group 3 medulloblastoma is one of the most aggressive types of childhood brain tumors. Roughly 30 % of cases carry genetic alterations in MYC, SMARCA4 or both genes combined. While overexpression of MYC has previously been shown to drive medulloblastoma formation in mice, the functional significance of SMARCA4 mutations and their suitability as a therapeutic target remain largely unclear. To address this issue, we combined an overexpression of MYC with a loss of SMARCA4 in cerebellar granule cell precursors. Cells were isolated from 7-day-old Math1-creERT2::Smarca4fl/fl pups after tamoxifen-induced loss of SMARCA4. Subsequently, MYC overexpression was achieved by lentiviral transduction, and transduced cells were transplanted into immunodeficient CD1nu/nu recipient mice. Preliminary results show tumor formation in 5/19 transplanted mice (26 %) after 6 months. SMARCA4 loss in all tumor cells was confirmed both immunohistochemically and on a genetic level and suggests a dependency of tumor growth on SMARCA4 loss. In a next step, additional cohorts will clarify if tumor development is accelerated by or even dependent on the loss of SMARCA4 in our model. Additionally, the neoplastic potential of tumor cells will be verified with the aid of secondary recipient mice. To evaluate to what extent the generated tumors are comparable to human Group 3 medulloblastomas, tumors will be extensively analyzed on a morphological, transcriptional, and epigenetic level. Altogether, we hope to establish a suitable mouse model for SMARCA4 mutated Group 3 medulloblastoma that will help to elucidate the role of SMARCA4 in tumor development and to identify new therapeutic targets.
MEDB-13. Neurocognitive and radiological follow-up of children under 5 years of age treated for medulloblastoma according to the HIT-SKK protocol
Authors: Merlin Marie-Sophie , Schmitt Emmanuelle , Mezloy-Destracque Malika , Dufour Christelle , Riffaud Laurent , Puiseux Chloé , De Carli Emilie , Bodet Damien , Icher Céline , Doz François , Faure-Conter Cécile , Pagnier Anne , Pluchart Claire , Thouvenin-Doulet Sandrine , Lejeune Julien , Thi-Lambert Phi-Linh Nguyen , Chastagner Pascal
Published: June 2022

BACKGROUND: HIT-SKK protocol is used for the treatment of low risk medulloblastomas in young children with the aim of eliminating cranial irradiation and its long-term side effects, in particular neuropsychological (NP) sequelae. This therapy includes IV and intraventricular (ITV) methotrexate (MTX) potentially responsible for leukoencephalopathy (LE) and neurocognitive disorders.The objectives are to describe the risk factors and the course of LE, and to investigate its impact on long-term neurocognitive and behavioural outcome. METHODS: A French retrospective, multicenter study including 35 children under 5 years of age, treated between 2009 and 2017, with a median follow up of 72 months. All follow-up MRIs including assessment of the severity of the LE (Fazekas and CTCAE grading) and all NP evaluations were centrally rewieved. RESULTS: 25/34 evaluable patients presented a LE during follow up, in a median delay of 2 months (1 - 17 months) after the start of chemotherapy. Grade 2 and 3 abnormalities were correlated with higher cumulative dose of ITV -MTX (p=0,01). Full Scale IQ (FSIQ) and Wechsler indexes were in the average or low average of the reference population. FSIQ was deficient in 7/20 evaluable patients. Processing speed (PSI) was the most frequently impaired neurocognitive domain: 9/20 patients with borderline or very low score, all having received a significantly higher cumulative dose of ITV-MTX (p=0,04). A decrease in overall NP scores was observed in patients for whom grade 2 or 3 LE persisted at the end of follow-up with an average FSIQ estimated at 82.1 (SD 16.9) versus 94.2 (SD 20.6). This decrease was significant for PSI (p=0,049). LE and neurocognitive impairments were not correlated with a younger age at diagnosis. CONCLUSION: This study confirmed the responsibility of MTX, and in particular ITV-MTX therapy in the onset and, most often, persistence of LE and its association with neurocognitive disorders.
MEDB-16. Persistent radiological lesions at the end of primary therapy in childhood medulloblastoma: residual lesion or active residual tumor?
Authors: Schömig Lena , Obrecht Denise , Mynarek Martin , Bison Brigitte , Schwarz Rudolf , Pietsch Torsten , Rutkowski Stefan , Benesch Martin
Published: June 2022

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-22. iPSC-derived cerebellar organoid model for hereditary genetic predisposition in SHH-medulloblastoma
Authors: Manz Frederik , Haag Daniel , Pfister Stefan M , Kutscher Lena
Published: June 2022

Medulloblastoma is one of the most common malignant embryonal brain tumors in children. Medulloblastomas of the Sonic Hedgehog (SHH) group arise from excessive proliferation of granule neuron progenitor (GNP) cells during cerebellar development. Genetic predisposition accounts for nearly 40% of all pediatric SHH-medulloblastomas. Recently, ELP1, a novel predisposition gene, was shown to be germline mutated in 15% of SHH-medulloblastoma patients. ELP1 encodes the scaffolding member of the Elongator complex and is required for efficient translation. Heterozygous mutations in ELP1 have been associated with the neural disorder Familial Dysautonomia, but not cancer. ELP1-associated medulloblastomas frequently harbor somatic PTCH1 co-mutations. It remains unclear how ELP1 affects the GNP lineage during normal cerebellar development and tumorigenesis in pediatric SHH-medulloblastoma patients. To characterize ELP1 mutations in the GNP lineage in vitro, we established a cerebellar organoid model from human induced pluripotent stem cells (iPSCs). We genetically inserted an EGFP reporter downstream of the endogenous GNP-specific ATOH1 locus in control iPSCs and generated cerebellar organoids according to published protocols. Marker gene and protein expression levels confirmed the cerebellar identity of the 3D model. Furthermore, activation of the EGFP reporter in single cells within the organoid highlighted the specification of putative GNPs. Next, we will determine the specific cell state of putative iGNPs and compare to human GNPs identified in our scRNAseq cerebellum atlas. To analyze tumorigenesis through ELP1 loss, we will introduce patient-specific ELP1mutations into ATOH1-EGFP iPSCs. Cerebellar organoids derived from ELP1-, PTCH1-deficient and control iPSCs will serve as models to study GNP proliferation, differentiation, apoptosis and tumor formation. Combining genome editing, in vitro 3D differentiation and functional studies, we will characterize the novel predisposition gene ELP1in GNPs during cerebellar development. In addition, we will determine the interplay of ELP1and PTCH1 co-mutations, predisposing SHH-medulloblastoma formation.
MEDB-26. Outcomes of children with standard-risk and high-risk medulloblastoma treated with pre-irradiation chemotherapy and risk-adapted craniospinal irradiation: a report on patients from the Polish Pediatric Neuro-oncology Group
Authors: Perek-Polnik Marta , Cochrane Anne , Chojnacka M , Drogosiewicz M , Filipek I , Swieszkowska E , Tarasinska M , Kowalczyk P , Abdelbaki Mohamed S , Dembowska-Bagińska Bożenna
Published: June 2022

BACKGROUND: The last two decades have witnessed several efforts to minimize the adverse sequelae of craniospinal irradiation (CSI), a standard of care treatment modality in medulloblastoma. This has been accomplished by adding chemotherapy to the treatment backbone. The use of pre-irradiation chemotherapy has also been previously reported. In one of the largest studies to date, we analyze treatment outcomes in children with standard and high-risk medulloblastoma treated with pre-irradiation chemotherapy followed by reduced-dose radiotherapy in SR and maintenance chemotherapy. METHODS: Data from the Polish Pediatric Neuro-oncology Group (PPNG) was analyzed in patients greater than 3 years of age with newly-diagnosed medulloblastoma. RESULTS : Among 138 patients, median age at diagnosis was 7.9 years and median follow-up was 5.5 years. Comprehensive molecular subgrouping was not available for all patients at the time of data collection. Of 60 standard-risk patients, there was pre-irradiation disease recurrence in one patient. One patient expired prior to radiation due to metastatic disease. Of 78 high-risk patients, one had pre-irradiation recurrence. Overall survival (OS) for high-risk patients at 3 and 5 years (± standard error) was 89.2 ± 4.0% and 81.3 ± 5.8%, respectively. OS for standard-risk patients at 3 and 5 years was 92.5 ± 3.8% and 88.2 ± 5.1%, respectively. Among high-risk patients, event-free survival (EFS) at 3 and 5 years was 82.5 ± 5.3% and 81.0 ± 5.6%. Among standard-risk patients, 3-year EFS was 89.2 ± 4.6% and 5-year EFS was 86.8 ± 5.3%. CONCLUSION : This study demonstrates promising survival outcomes in pediatric medulloblastoma patients treated with pre-irradiation chemotherapy followed by reduced-dose CSI and adjuvant chemotherapy. Such an approach may be helpful if delays in starting radiotherapy are expected, which is usually the case in many institutions around the globe.
MEDB-30. Subclassification of Group 3/4 medulloblastoma as a potential prognostic biomarker to reduce the dose of craniospinal irradiation in patients with metastatic tumors: A Japanese Pediatric Molecular Neuro-Oncology Group study
Authors: Fukuoka Kohei , Kurihara Jun , Mori Makiko , Arakawa Yuki , Yoshioka Ema , Shofuda Tomoko , Matsushita Yuko , Hibiya Yuko , Honda Satoko , Nakazawa Atsuko , Kiyotani Chikako , Kagawa Naoki , Yamasaki Kai , Ando Ryo , Keino Dai , Miyairi Yosuke , Akai Takuya , Kanamori Masayuki , Ishida Joji , Park Young-Soo , Kawamura Atsufumi , Sasaki Atsushi , Nishikawa Ryo , Date Isao , Nagane Motoo , Koh Katsuyoshi , Ichimura Koichi , Kanemura Yonehiro
Published: June 2022

BACKGROUND: In patients with medulloblastoma, one of the most significant challenges is to reduce the dose of craniospinal irradiation (CSI) to minimize neurological sequelae in survivors. Molecular characterization of patients treated using lower-dose CSI rather than standard therapy is important for further reducing the treatment burden. METHODS: We conducted DNA methylation analysis using an Illumina Methylation EPIC array to investigate molecular prognostic markers in 38 patients with medulloblastoma who were registered in the Japan Pediatric Molecular Neuro-Oncology Group and were treated using lower-dose CSI rather than standard-dose radiation therapy. RESULTS: Among the patients, 23 were classified as having a “standard-risk” and 15 as having a “high-risk” according to the classic classification based on tumor resection rate and presence of metastasis, respectively. The median follow-up period was 71.5 months. The median CSI dose was 18 Gy in both groups, and 10 patients in the “high-risk” group received a CSI dose of 23.4 Gy or 24 Gy. Molecular subgrouping revealed the “standard-risk” cohort included 5 WNT, 2 SHH, and 16 Group 3/4 cases; all 15 patients in the “high-risk” cohort had Group 3/4 medulloblastoma. Among the patients with Group 3/4 medulloblastoma, 13 of the 16 “standard-risk” patients were subclassified as subtypes I, IV, VI, and VII, which were associated with a good prognosis according to the novel sub-subclassification among Group 3/4 medulloblastomas. However, only 6 of the 15 “high-risk” patients were included in the subtypes. The good prognostic subtype cases among “high-risk” cohort were all survived without recurrence, in contrast to a worse prognosis (5-year progression free survival=33.3%; p=0.01) of the other cases. CONCLUSION: Although these findings require validation in a larger cohort, the present findings suggest that the novel sub-subclassification of Group 3/4 medulloblastoma may be a promising prognostic biomarker for reducing the dose of CSI in patients with metastatic medulloblastoma.
MEDB-31. THE CLINICAL SIGNIFICANCE OF EXTENT OF RESECTION IN MEDULLOBLASTOMA
Authors: Keeling Claire , Davies Simon , Hicks Debbie , Clifford Steven
Published: June 2022

Medulloblastoma (MB) patients determined to have a sub-total resection (STR), defined by >1.5cm2 post-surgical tumour residuum, receive intensified treatment regimes, but recently the designation of STR as a high risk feature is being questioned. We aimed to assess the clinical correlates of extent of resection (EOR) and its impact on survival, with particular consideration of EOR in relation to the four MB consensus molecular subgroups (WNT, SHH, Group 3, Group 4). We collected data from 1113 patients (n=419, UK CCLG institutions; n=694, published data) representing the largest ever combined cohort constructed to assess the impact of EOR in medulloblastoma. We performed association analyses and univariate/multivariate survival analysis using Kaplan-Meier, log-rank and Cox proportional hazard modelling, analysing overall survival (OS) cohort-wide and with reference to molecular subgroups and clinical features. Association analysis of the combined cohort evidenced that infant patients were more likely to have STR (p=0.02). In this whole-cohort analysis, EOR was significantly associated with survival in univariate analysis (HR 1.64, 95% CI 1.30-2.07, p=<0.001) but not in multivariate analysis. STR was variably prognostic in sub-cohort analyses of specific demographics and molecular subgroup; worse outcomes were observed in patients <5 years in SHH (p=0.044) and Group 4 (p=0.044). This was true for WNT patients >5 years old at diagnosis (p=0.034) although numbers were small and require validation in even larger cohorts. In this cohort of >1100 MBs, STR was significantly associated with a lower OS in univariate analysis, but this was driven by specific disease contexts (SHH and Group 4 patients <5 years old). STR was not independently prognostic overall or in any setting. We recommended that surgeons should continue to pursue maximal safe resection for all MB patients but suggest that consideration of STR as a high-risk feature should be disease context specific.
MEDB-35. Relationship between genetic profile, histology, clinical features and long-term outcome in young children medulloblastoma (YCMB) treated with upfront high dose chemotherapy (HDCT) in Italy
Authors: Garrè Maria Luisa , Massimino Maura , Buttarelli Francesca Romana , Gandola Lorenza , Barra Salvina , Giangaspero Felice , Goschzik Tobias , Biassoni Veronica , Pastorino Lorenza , Pistorio Angela , Pietsch Torsten
Published: June 2022

AIMS: We report a cohort of YCMB cases homogeneously treated with HDCT in two Italian institutions, and the prognostic impact of histology and genetics retrospectively evaluated. METHODS: All YCMB (aged≤3 years) treated with upfront HDCT in the period 1998-2019 were included, reclassified according to the WHO2021 classification of CNS tumours. Mutational status ofPTCH1, SUFU, and TP53 was analysed in selected cases. Histology and genetics were correlated with survival, secondary tumours(STs), and cancer predisposition syndromes(CPSs). RESULTS: Fifty-three patients were enrolled (62.3% male), median age 2.2 years. 21 had classic(CMB), 15 desmoplastic/nodular(DMB), 11 MBEN and 6 large-cell/anaplastic(AMB/LCMB) medulloblastoma. Metastases were present in 18. Genomic pattern showed SHH-TP53wt in 29 cases, non-WNT/non-SHH in 22; 2 were SHH-TP53mut. Induction chemotherapy (VCR/HDMTX, HDVP16, VCR/HDCTX and HDCARBO) was followed by 2-3 HDCT courses; irradiation reserved to cases with metastatic disease and/or residual tumours. 22 patients never received irradiation. SHH-TP53wt cases had significantly less metastasis (p=0.002), while non-WNT/non-SHH received more often irradiation (p<0.0001). OS at 5, 10, and 20 yrs was 0.73, 0.70 and 0.57 respectively in the entire cohort; stable at 0.85 (at 5, 10, and 20 yrs) in SHH-TP53wt patients while 0.58, 0.51 and 0.17 in the non-WNT/non-SHH. PFS at 5, 10, 20 yrs was stable at 0.89 in SHH-TP53wt and remained 0.35 in non-WNT/non-SHH. 13/53 patients presented Gorlin Syndrome; 1 had familial MB. 16 STs were reported in 14 cases; life-threatening, irradiation-related STs mainly in non-WNT/non-SHH cases. In SHH-TP53wt benign tumours or related to CPS were reported. CONCLUSIONS: This is one of the first series of YCMB treated with HDCT without stratification for stage and histology. The long follow-up highlights the frequency/types of associated CPS and STs; the latter, in non-WNT/non-SHH, were treatment-related and life-threatening.
MEDB-37. Chemotherapy response prediction by molecular risk factors in metastatic childhood medulloblastoma
Authors: Obrecht Denise , Bockmayr Michael Ludwig , Bison Brigitte , Pfister Stefan M , Sturm Dominik , Sahm Felix , Jones David T W , Sill Martin , von Hoff Katja , Benesch Martin , Gerber Nicolas U , von Bueren André , Friedrich Carsten , Pietsch Torsten , Schüller Ulrich , Mynarek Martin , Rutkowski Stefan
Published: June 2022

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<0.01 / 5-year OS responder: 80.0±4.2%, non-responder: 45.9±8.0%, p<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<0.01). We identified a very-high-risk-cohort (any two criteria of: <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<0.01/p<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-38. Significance of CSF cytology and neurologic deterioration in relapsed medulloblastomas in the German HIT-REZ-97/-2005 Studies and the HIT-REZ-Register
Authors: Tschirner Sebastian , Adolph Jonas E , Gaab Christine , Tippelt Stephan , Mikasch Ruth , Mynarek Martin , Rutkowski Stefan , Pietsch Thorsten , Bison Brigitte , Warmuth-Metz Monika , Pfister Stefan M , Milde Till , Pajtler Kristian W , Witt Olaf , Frühwald Michael , Kramm Christof , Schlegel Paul-Gerhardt , Kortmann Rolf-Dieter , Dietzsch Stefan , Timmermann Beate , Fleischhack Gudrun
Published: June 2022

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
MEDB-42. GermlineElp1 deficiency promotes genomic instability and survival of granule neuron progenitors primed for SHH medulloblastoma pathogenesis
Authors: Garcia-Lopez * Jesus , Ahmad * Shiekh Tanveer , Li * Yiran , Gudenas Brian , Kojic Marija , Manz Friedrik , Jonchere Barbara , Mayasundari Anand , Pitre Aaron , Hadley Jennifer , Paul Leena , Batts Melissa , Bianski Brandon , Tinkle Christopher , Orr Brent , Rankovic Zoran , Robinson Giles , Roussel Martine , Wainwright Brandon , Kutscher Lena , Lin # Hong , Northcott # Paul
Published: June 2022

Germline loss-of-function (LOF) mutations in Elongator complex protein 1 (ELP1) are found in 15-20% of childhood SHH medulloblastoma (MB) and are exceedingly rare in non-SHH-MB or other cancers. ELP1 germline carriers that develop SHH-MB harbor frequent somatic PTCH1 mutations and universally sustain loss-of-heterozygosity of the remaining ELP1 allele through chromosome 9q deletion. ELP1 functions as a scaffolding subunit of the Elongator complex that is required for posttranscriptional modification of tRNAs and maintenance of efficient translational elongation and protein homeostasis. However, the molecular, biochemical, and cellular mechanisms by which ELP1/Elongator LOF contribute to SHH-MB tumorigenesis remain largely unknown. Herein, we report that mice harboring germline Elp1 monoallelic loss (i.e., Elp1+/-) exhibit hallmark features of malignant predisposition in developing cerebellar granule neuron progenitors (GNPs), the lineage-of-origin for SHH-MB. Elp1+/- GNPs are characterized by increased replication stress-induced DNA damage, upregulation of the homologous recombination repair pathway, aberrant cell cycle, and attenuation of p53-dependent apoptosis. CRISPR/Cas9-mediated Elp1 and Ptch1 gene targeting in mouse GNPs reproduces highly penetrant SHH-MB tumors recapitulating the molecular and phenotypic features of patient tumors. Reactivation of the p53 pathway through MDM2 and PAK4 inhibitors promotes selective cell death in patient-derived xenograft tumors (PDX) harboring deleterious ELP1 mutations. Together, our findings reveal that germline Elp1 deficiency heightens genomic instability and survival in GNPs, providing a mechanistic model for the subgroup-restricted pattern of predisposition and malignancy associated with pathogenic ELP1 germline carriers. These results provide rationale for further preclinical studies evaluating drugs that overcome p53 pathway inhibition in ELP1-associated SHH-MB and a renewed outlook for improving treatment options for affected children and their families.*, # Contributed equally
MEDB-43. Development of a bioinformatics pipeline for identification of differential DNA methylation events associated with medulloblastoma relapse
Authors: Kui Christopher , Richardson Stacey , Schwalbe Edward C , Thompson Dean , Keeling Claire , Strathdee Gordon , Dufour Christelle , Bailey Simon , Ramaswamy Vijay , Clifford Steven C , Hill Rebecca M
Published: June 2022

Relapsed medulloblastoma (rMB) is treatment-resistant and fatal in ~95% of cases. The epigenetic features of rMB, and any role as drivers of disease relapse/treatment-resistance have yet to be investigated. We therefore developed a pipeline to identify differentially methylated CpGs (DM-CpGs) and regions (DMRs) in a paired-rMB cohort. Our paired-rMB cohort (n=61, relapsed tumours matched with diagnosis counterparts) with available Illumina Methylation 450K/850K microarray data was processed in R-Studio. The packages Limma and DMRcate were used to perform a paired differential methylation analysis on a filtered selection of array probes (n=335,767), identifying DM-CpGs and DMRs with a 5% FDR. DMRs were further retained if they had a maximum-Δβ of >0.2 and correlated with locus-specific gene expression in a separate paired DNA-methylation array/RNA-seq cohort from medulloblastoma diagnosis samples (n=202). Finally, we created univariable Cox models to assess the prognostic potential of DM-CpGs/DMRs in an independent survival cohort of medulloblastoma diagnosis samples (n=498). Across the paired-rMB cohort, there were few significant differential methylation events initially identified at relapse (n=258 DM-CpGs, n=32 DMRs). Upon sub-analysis by molecular group, MBGroup4 (n=18 pairs) alone yielded significant findings (n=189 DM-CpGs, n=26 DMRs). Most changes involved hypermethylation events detected at relapse. Multiple DM-CpGs identified at relapse were prognostic for both overall and event-free survival when assessed in our independent cohort (n=22 whole cohort, n=13 Group 4, BH-adjusted p<0.05). When applying the DMR filters, only the MBGroup4 DMRs passed the Δβ filter (n=18/26), with few correlating with gene expression (n=2, p<0.001), and none demonstrating prognostic significance. This pipeline facilitates exploration of the clinical relevance of epigenome-wide changes in a paired-rMB cohort. We highlight the potential prognostic significance of DM-CpGs, and future work will explore the potential functional role of candidate-genes associated with our DMRs, as novel drivers of rMB.
MEDB-49. Relapsed SHH medulloblastomas in young children. Are there alternatives to full-dose craniospinal irradiation?
Authors: Erker Craig , Craig Brandon , Bailey Simon , Massimino Maura , Larouche Valerie , L Finlay Jonathan , Kline Cassie , Michaiel George , Margol Ashley , Cohen Kenneth , Cacciotti Chantel , Harrods Virginia , Doris Kathleen , AbdelBaki Mohammed , Amayiri Nisreen , Wang Zhihong , Hansford Jordan , Hukin Juliette , Salloum Ralph , Hoffman Lindsay , Muray Jeffrey , Ginn Kevin , Zapotocky Zapotocky , Baroni Lorena , Ramaswamy Vijay , Gilheens Stephen , Aguiera Dolli , Mazewski Claire , Shah Shafqat , Strother Douglas , Muller Sabine , Gajjar Amar , Northcott Paul , Clifford Steve , Robinson Giles , Bouffet Eric , Lafay-Cousin Lucie
Published: June 2022

BACKGROUND/RATIONAL: Following initial irradiation sparing therapy, many young children with relapsed medulloblastoma can be salvaged with craniospinal irradiation (CSI). However, the interval to relapse is short and neurocognitive sequelae remain a major concern. The contribution of molecular subgrouping may help refine indications and modalities of salvage strategies in this population. METHOD: From a cohort of 151 young children with molecularly characterized relapsed medulloblastoma, subset analysis of the SHH medulloblastoma was conducted to describe the practice of salvage radiotherapy and associated post-relapse survival (PRS). RESULTS: Sixty-seven SHH medulloblastoma patients (46 M0; 54 GTR; 11 non-ND/MBEN) received salvage therapy with curative intent. Before relapse, 54 (80.6%) received conventional chemotherapy (CC), 13 (19.4%) high-dose chemotherapy (HDC), while seven had additional focal radiotherapy (fRT). Median time to relapse was 11.1 months (range 3.8-41.0) and 43.3% were localized. Thirty patients (16 localized relapse) underwent surgery. Forty-seven (71.2%) received salvage radiotherapy (20 with CC; 10 with HDC; 15 alone, two unknown). CSI and fRT accounted for 82% and 18% respectively. CSI median dose was 36Gy (range 18-39Gy). Ten patients (eight with localized relapse) received CSI doses ≤23.4Gy. Nineteen patients (28.8%) did not receive any radiotherapy (nine HDC; 10 CC only). Radiotherapy was associated with better 3-year PRS (73.0% versus 36.1%; p=0.001). All patients treated with CSI ≤ 23.4Gy were alive at median follow-up of 69 months(24-142). Six of nine patients treated with HDC without irradiation were alive at last follow-up. Sixty-three percent of patients received reduced dose CSI(≤23.4Gy), fRT, or no radiotherapy, and their PRS did not significantly differ from those who received CSI ≥ 30.6Gy (p = 0.54). CONCLUSION: While salvage CSI provided PRS benefit in this SHH medulloblastoma cohort, we report the use of reduced salvage radiotherapy and irradiation avoidance in 63% of the patients, with 60% alive at last follow-up.
MEDB-54. Standard Risk Medulloblastoma treated solely with surgery and chemo-radiation
Authors: Cantor Evan , Meyer Ashley , Ogle Andrea , McHugh Michele , Beck Mary , Green Tammy , Ramachandran Lakshmi , Dahiya Sonika , Cluster Andrew , Brossier Nicole M , Abdelbaki Mohamed S , Limbrick David , Perkins Stephanie , Shatara Margaret
Published: June 2022

INTRODUCTION: Medulloblastoma is the most common malignant brain tumor in children, with 5-year overall survival (OS) ranging from 60%-95% depending on subgroup and risk status. The POG 8631/CCG 923 trial (accrual 1986-1990) found a 63% 5 year OS for patients with local disease after gross total resection treated with radiation at a dose of 23.4 Gy craniospinal radiation and posterior fossa boost to 54 Gy, vs. 80.5% 5-year OS for patients treated as per full ACNS0331 therapy including maintenance chemotherapy. Herein, we describe a long-term survival with standard-risk medulloblastoma who only received surgical resection and radiation therapy. CASE: A 17-year-old male presented with acute onset of hypertension, bradycardia, headache, and blurry vision and was found to have a heterogeneously enhancing posterior fossa mass with mass effect on the fourth ventricle and hydrocephalus on brain MRI. He underwent gross total resection of the tumor and histopathology revealed medulloblastoma with classic and large cell features. Fluorescence in situ hybridization (FISH) was negative for MYC, MYCN amplification, or HER2 gain. Cerebrospinal fluid cytology was negative for neoplastic cells, and spinal MRI did not reveal any drop metastases. The patient initiated therapy per ACNS0331 with craniospinal irradiation posterior fossa boost. He also received weekly vincristine. After completion of radiation therapy, the family declined further chemotherapy despite medical advice. He had no evidence of relapse most recently at 51 months from completion of therapy. Next generation sequencing and methylation testing are currently pending. CONCLUSION: Current efforts aim at optimizing therapy based on molecular subgrouping, to minimize long-term adverse events associated with current therapies. We report a unique case of an adolescent male with an standard-risk medulloblastoma, who achieved remission with only radiotherapy. Further molecular tumor analysis may elucidate the response of the tumor.
MEDB-55. Single-cell transcriptomics reveals progenitor cells expressing a photoreceptor program as putative cells origin of MYC-driven Group 3 Medulloblastoma
Authors: Zhao Miao , Mainwaring Oliver , Rosén Gabriela , Elgendy Ramy , Doroszko Milena , Rijpkema Sanne , Sundstrom Anders , Nelander Sven , Weishaupt Holger , Furukawa Takahisa , Swartling Fredrik J
Published: June 2022

Brain tumors are the leading cause of childhood cancer-related death. Medulloblastoma is the most common malignant pediatric brain tumor with about 70% survival. Medulloblastoma comprises four distinct subgroups respective of genomic and molecular drivers influencing tumorigenesis. It has been established that despite being considered a single disease entity, each subgroup arises from a distinct population of cells found within unique compartments of the developing brain. The cell of origin of Group 3 medulloblastoma, the most malignant medulloblastoma subgroups, is currently unknown and remains controversial. Transcriptional profiling has revealed that Group 3 medulloblastomas are characterized by elevated expression of a photoreceptor program, which has not been described in the normal cerebellar development but is well characterized in the developing pineal gland and retinal. By investigating and comparing brain and tumor development between our previously developed medulloblastoma mice model (GMYC), where mice spontaneously develop Group 3 medulloblastoma after 4-6 months of age, and their control counterparts, we found that tumor cells emerged from progenitor cells where MYC overexpression drove the transformation of immature progenitor cells expressing a photoreceptor program. Our data suggest that MYC-driven Group 3 medulloblastoma originates from progenitor cells expressing a photoreceptor program, which has implications for future research and the development of novel treatments targeting this devastating childhood malignancy.
MEDB-64. Are Rab GTPases metastatic drivers in metastatic medulloblastoma?
Authors: Entwistle Susannah , Jackson Hannah K , Kerr Ian , Coyle Beth , Hume Alistair
Published: June 2022

Medulloblastoma is the most common malignant paediatric brain cancer with poorer prognosis related to the onset of metastasis. It has four molecular subgroups; Wingless (WNT), Sonic Hedgehog (SHH), group 3 and group 4, of which group 3 is the most likely to be metastatic and is therefore associated with the poorest prognosis. Exosomes are small membrane-bound extracellular vesicles of endosomal origin which contain a variety of cargo including RNA and proteins. Increased exosome release is connected with disease progression and metastasis in multiple cancers. Rabs are a family of small GTPases (70 in humans) which regulate vesicle trafficking. Several Rabs are known to regulate exosome biogenesis and secretion and may thereby contribute to cancer progression. The role of Rabs in metastatic medulloblastoma is unclear. We aim to explore whether Rabs contribute to the progression of metastatic medulloblastoma through the exosome biogenesis and secretion pathways. Through analysis of literature, databases such as ExoCarta.org, the R2: Genomics analysis and visualisation platform, and mRNA content of medulloblastoma exosomes, five novel Rab candidates were identified that may contribute to disease progression in group 3 medulloblastoma. Gene expression of these Rabs was then verified across SHH, group 3 and group 4 patient-derived cell lines using RT-qPCR, with candidate Rab expression confirmed in the three subgroups. Presence of Rab mRNA has also been found in exosomes derived from group 3 and group 4 patients, with an enrichment in group 3 exosomes. Current and future work aims to determine the potential roles of Rabs in medulloblastoma pathogenesis, and to determine whether Rabs contribute to increased exosome biogenesis which drives metastasis or are metastatic drivers in medulloblastoma themselves. Therefore, experiments to characterise Rab candidate protein expression within cells and assess their function after knockdown are necessary and timely.
MEDB-65. Molecular subclassification of a national cohort of pediatric medulloblastoma based on methylation profile
Authors: Alaña Lide , Martin-Guerrero Idoia , Navajas Aurora , Zaldumbide Laura , Mosteiro Lorena , Schwalbe Edward C , Hicks Debbie , Clifford Steven C , García-Ariza Miguel
Published: June 2022

INTRODUCTION: Pediatric Medulloblastoma (MB) accounts for approximately 20% of all childhood brain tumors. Molecular subgroups namely WNT, SHH, Group 3 and Group 4, exhibit divergent biology, and clinical outcomes. DNA methylation analysis is a robust option to classify pediatric MB into molecular subgroups, which allows the optimization of diagnosis and stratification of the treatment. We review the first experience of molecular subclassification carried out at the national level in our country. METHODS: Multi-center centralized prospective and retrospective study of frozen tumor samples at diagnosis from pediatric MB patients diagnosed in Spanish hospitals, from April 2021 to December 2021. A registry was created with histology review, immunohistochemical (IHC) subgrouping, and a molecular subgrouping based on the Minimal Methylation Classifier (MIMIC) from Schwalbe et al., 2017. The time from the sample centralized reception to the study result was also collected. RESULTS: 25 frozen MB tumor samples from patients at diagnosis were included. 6 were retrospective and 19 prospective. IHC classified 19 cases (76%) as non-WNT/non-SHH MBs, 3 (12%) as WNT-activated and 3 (12%) as SHH-activated. MIMIC classified, in the non-WNT/non-SHH, 6 tumors (24%) as Group 3 and 13 (52%) as Group 4. 2 cases (8%) were WNT-activated MBs and 3 (12%) were SHH-activated MBs. Only 1 case (4%) was unclassified by MIMIC (WNT using IHC). Comparing both methods (IHC and MIMIC), diagnosis agreed in 96% of cases. The response time ranged from 5 to 10 days. CONCLUSIONS: DNA methylation profiling has proven to be a robust and quick option to classify MB into subgroups and it correlates with the IHC diagnosis. This tool was successfully implemented in our national routine diagnosis, enabling a reliable and rapid molecular subgrouping classification.
MEDB-71. Molecular characterisation of group 4 medulloblastoma improves risk-stratification and its biological understanding
Authors: Goddard Jack , Castle Jemma , Southworth Emily , Fletcher Anya , Crosier Stephen , Martin-Guerrero Idoia , Garcia-Ariza Miguel , Navajas Aurora , Masliah-Planchon Julien , Bourdeaut Franck , Dufour Christelle , Goschizk Tobias , Pietsch Torsten , Richardson Stacey , Hill Rebecca M , Williamson Daniel , Bailey Simon , Schwalbe Edward C , Clifford Steven C , Hicks Debbie
Published: June 2022

Group 4 (MBGrp4) accounts for ~40% of medulloblastoma and the majority of non-WNT/non-SHH cases, yet its underpinning biology is poorly understood, and survival outcomes are not sufficiently explained by established clinico-pathological risk factors. We investigated the clinical and molecular correlates of MBGrp4, including second-generation methylation non-WNT/non-SHH subtypes (I-VIII) and whole chromosome aberration (WCA) subtypes (defined by chromosome 7 gain, 8 loss, and 11 loss; WCA-favourable risk [WCA-FR] ≥2 features, WCA-high risk [WCA-HR] ≤1 feature). A clinically-annotated MBGrp4 discovery cohort (n=378) was assembled from UK CCLG institutions, collaborating centres and SIOP-UKCCSG-PNET3/HIT-SIOP-PNET4 clinical trials. Contemporary molecular profiling integrating methylation/WCA subtypes and next-generation sequencing was performed. Survival modelling was carried out with patients >3 years old who received craniospinal irradiation (n=336). Association analysis confirmed relationships between methylation and WCA subtypes. Subtypes VI and VII were enriched for WCA-FR (p<0.0001) and aneuploidy, whereas subtype VIII was defined solely by i17q (p<0.0001). Whilst we observed an overall low mutational burden, WCA-HR harboured recurrent mutations in genes involved in chromatin remodelling (p=0.007). No gene-specific events were associated with disease risk, however integration of both methylation subtype and WCA groups enabled improved risk-stratification survival models that outperformed current schemes. The optimal MBGrp4-specific model stratified patients into: favourable-risk (local disease, subtype VII or subtype VI with WCA-FR; 39/194 [20%], 97% 5-year PFS), very-high-risk (metastatic disease with WCA-HR; 71/194 [37%], 50% 5-year PFS) and high-risk (remaining patients; 84/194 [43%], 67% 5-year PFS). Findings were validated in independent cohorts. Comprehensive clinico-molecular assessment of MBGrp4 provides important understanding of its clinical and biological heterogeneity. Our novel MBGrp4 stratification scheme removes standard risk disease and identifies a favourable risk group (20% of MBGrp4) with potential for therapy de-escalation. Current therapeutic strategies are insufficient for the very-high risk group (encompassing 37% of MBGrp4), for whom novel therapies are urgently required.
MEDB-72. MOLECULAR CHARACTERIZATION OF MEDULLOBLASTOMAS IN A SINGLE INSTITUTION
Authors: Tan Enrica E K , Tan Mui Li , Kuick Chik Hong , Yong Min Hwee , Low Sharon Y Y , Chang Kenneth T E , Tan Char Loo
Published: June 2022

INTRODUCTION: The four molecular groups (WNT, SHH, Group 3 and Group 4) in medulloblastoma have been well established for the past decade. New subgroups within the four principal molecular groups have recently been discovered and recognized by WHO classification of Central Nervous System Tumours (5th edition). Subgroups were reported to have distinct somatic copy-number aberrations and clinical outcomes. This further classification could be helpful to refine prognostication and potentially provide risk stratification for treatment planning. AIM: To interrogate archival medulloblastoma samples using Oncoscan Microarray Assay, correlate with clinical features and consider the assay for clinical use. METHODS: Thirty-one archival samples with histological diagnosis of medulloblastoma and molecular grouping results from NanoString were retrieved and evaluated with Oncoscan Microarray Assay. Twenty-six were subjected to DNA methylation profiling to compare the results. Eight cases also had molecular data from next-generation sequencing (NGS) done with the in-house Ampliseq Childhood Cancer Panel. Correlation was made with clinical characteristics and outcomes of these 31 patients. RESULTS: OncoScan microarray showed distinct differences in the copy number profiles of the 31 medulloblastoma samples. Seventeen samples could be further classified into one of 12 subgroups. However, further subgrouping was challenging without first determining the main molecular group especially amongst non-WNT/SHH tumours. DNA methylation results provided corroboration with the Oncoscan subgrouping results in 25 of 26 samples. NGS panel detected additional genetic alterations in 5 of 8 samples. CONCLUSIONS: Oncoscan Microarray Assay showed potential in providing additional molecular information for further subgrouping of medulloblastoma, but was insufficient for determining the main molecular groups. Moving forward, molecular characterization could instead be done through use of NGS panel and DNA methylation, which provides tumour epigenetic profiling on top of copy number variants. These could be used alongside the NanoString platform, which is performed routinely for all medulloblastomas at our centre.
MEDB-75. Treatment-induced pulmonary toxicity in patients with medulloblastoma: a retrospective analysis on 2 Italian institutions’ cohorts
Authors: Biassoni Veronica , Busia Alessandra , Barretta Francesco , Gandola Lorenza , Vennarini Sabina , Meroni Silvia , Mastronuzzi Angela , Del Baldo Giada , Chiesa Silvia , Pignoli Emanuele , Terenziani Monica , Pecori Emilia , Schiavello Elisabetta , Massimino Maura
Published: June 2022

BACKGROUND: Incidence of iatrogenic pulmonary toxicity is around 20%. Apart from bleomycin fibrosis, the role of lomustine, HD-thiotepa, autologous stem-cells transplantation(APBSCT) and their synergy with craniospinal irradiation(CSI) are unclear. To elucidate their role in lung-function impairment, we retrospectively evaluated 39 medulloblastoma patients treated at INT-Milan and OPBG-Rome. METHODS: 39 patients (17 females, median RT age 8 years) treated for localized(29) or metastatic(10) medulloblastoma in 2000-2020 and with spirometric assessment, were considered. Treatment included: SIOP-like-PNET IV(19), high-risk protocol(19), infant protocol without RT(1). CSI doses were: 23.4Gy(20), 31.2Gy(8), 36Gy(6) and 39Gy(4); 4 received protons and 34 photons(9 VMAT, 25 3D), 11 hyperfractionated-accelerated-RT; 33 had 6 median CCNU cycles; 6 APBSCT. RESULTS: Median follow-up: 98 months. All patients performed at least one spirometry at median 5 years after RT. Eight (20.6%) had mildly pathological spirometries, 8 Forced Vital Capacity (FVC%)<90%. RT age was not associated with FVC%/ PEF% (p=0.319 and 0.405). A lower Peak Expiratory Flow(PEF%) was marginally associated to APBSCT group (p=0.062) with FVC%(≤90% vs >90%) similar but less significant(p=0.163). Median FVC%/PEF% were higher in the CCNU-group without reaching significance (p=0.436 and 0.062): this was a standard-risk group not receiving APBSCT nor higher RT doses. Even though the lung volume encompassed by 5-10 Gy isodoses was greater in VMATvs3D RT(p<0.001 and p=0.015), there were no significant differences in ventilatory parameters. FVC%/PEF% were negatively associated to CSI dose. Since no relevant lung volume is involved in high doses, a multifactorial etiology could be speculated. CONCLUSIONS: Preliminary data show no significant FVC%/PEF% reduction. Small sample size and differences in spirometry techniques impose larger cohorts accrual to elucidate potential treatment-induced pulmonary impairment in the pediatric population thus validating the use of spirometry during treatment/follow-up.