Spectrum and prevalence of genetic predisposition in medulloblastoma: a retrospective genetic study and prospective validation in a clinical trial cohort

Molecular Characterization of Medulloblastoma in a Patient with Neurofibromatosis Type 1: Case Report and Literature Review

Brain tumors are the most common solid neoplasms of childhood. They are frequently reported in children with Neurofibromatosis type 1 (NF1). The most frequent central nervous system malignancies described in NF1 are optic pathway gliomas and brainstem gliomas. Medulloblastoma (MB) in NF1 patients is extremely rare, and to our knowledge, only 10 cases without molecular characterization are described in the literature to date. We report the case of a 14-year-old girl with NF1 that came to our attention for an incidental finding of a lesion arising from cerebellar vermis. The mass was completely resected, revealing a localized classic medulloblastoma (MB), subgroup 4. She was treated as a standard-risk MB with a dose-adapted personalized protocol. The treatment proved to be effective, with minor toxicity. Brain and spine MRI one year after diagnosis confirmed the complete remission of the disease. To our knowledge, this is the only case of MB reported in a patient with NF1 with molecular characterization by the methylation profile. The association between NF1 and MB, although uncommon, may not be an accidental occurrence.

Medulloblastoma and familial adenomatous polyposis: Good prognosis and good quality of life in the long-term?

INTRODUCTION

Mutations of the APC (adenomatous polyposis coli) gene correlate mainly with familial adenomatous polyposis (FAP), but can occasionally be pathogenic for medulloblastoma (MBL) wingless-related integration site (WNT) subtype, the course of which has only recently been described.

METHODS

We retrieved all patients with documented germline APC mutations and a diagnosis of MBL to examine their outcome, late effects of treatment, and further oncological events.

RESULTS

Between 2007 and 2016, we treated six patients, all with a pathogenic APC variant mutation and all with MBL, classic histotype. None had metastatic disease. All patients were in complete remission a median 65 months after treatment with craniospinal irradiation at 23.4 Gy, plus a boost on the posterior fossa/tumor bed up to 54 Gy, followed by cisplatin/carboplatin, lomustine, and vincristine for a maximum of eight courses. Five of six diagnostic revised MRI were suggestive of the WNT molecular subgroup typical aspects. Methylation profile score (in two cases) and copy number variation analysis (chromosome 6 deletion in two cases) performed on four of six retrieved samples confirmed WNT molecular subgroup. Four out of six patients had a positive family history of FAP, while gastrointestinal symptoms prompted its identification in the other two cases. Four patients developed other tumors (desmoid, MELTUMP, melanoma, pancreatoblastoma, thyroid Tir3) from 5 to 7 years after MBL.

DISCUSSION

Our data confirm a good prognosis for patients with MBL associated with FAP. Patients' secondary tumors may or may not be related to their syndrome or treatment, but warrant adequate attention when planning shared guidelines for these patients.

Embryonal Tumors of the Central Nervous System: The WHO 2016 Classification and New Insights

Central nervous system tumors comprise 26% of cancer in children, representing the most frequent solid neoplasms. Embryonal tumors comprise 15% of them, and they are defined as "small round blue cells" in which morphology is reminiscent of the developing embryonic nervous system. They are the most common high-grade central nervous system neoplasms. Over the years, molecular research has been improving our knowledge concerning these neoplasms, stressing the need for tumor reclassification. Indeed, the revised 2016 fourth edition of the World Health Organization classification introduced genetic parameters in the classification. Specific molecular signatures allow a more accurate risk assessment, leading to proper therapeutic approach and potentially improved prognosis. Holding this new approach, medulloblastoma is noteworthy. The present classification combines the previous histologic classification with a new genetic definition in WNT-activated, sonic hedgehog-activated and non-WNT/non-sonic hedgehog. Molecular data are also a defining feature in the diagnosis of atypical teratoid/rhabdoid tumors and embryonal tumors with multilayered rosettes. However, there are still embryonal tumors that challenge the present World Health Organization classification, and new molecular data have been underlining the need for novel tumor entities. Likewise, recent research has been highlighting heterogeneity in recognized entities. How to translate these molecular developments into routine clinical practice is still a major challenge.

A Survey of Compound Heterozygous Variants in Pediatric Cancers and Structural Birth Defects

Compound heterozygous (CH) variants occur when two recessive alleles are inherited and the variants are located at different loci within the same gene in a given individual. CH variants are important contributors to many different types of recessively inherited diseases. However, many studies overlook CH variants because identification of this type of variant requires knowing the parent of origin for each nucleotide. Using computational methods, haplotypes can be inferred using a process called "phasing," which estimates the chromosomal origin of most nucleotides. In this paper, we used germline, phased, whole-genome sequencing (WGS) data to identify CH variants across seven pediatric diseases (adolescent idiopathic scoliosis: n = 16, congenital heart defects: n = 709, disorders of sex development: n = 79, ewing sarcoma: n = 287, neuroblastoma: n = 259, orofacial cleft: n = 107, and syndromic cranial dysinnervation: n = 172), available as parent-child trios in the Gabriella Miller Kids First Data Resource Center. Relatively little is understood about the genetic underpinnings of these diseases. We classified CH variants as "potentially damaging" based on minor allele frequencies (MAF), Combined Annotation Dependent Depletion scores, variant impact on transcription or translation, and gene-level frequencies in the disease group compared to a healthy population. For comparison, we also identified homozygous alternate (HA) variants, which affect both gene copies at a single locus; HA variants represent an alternative mechanism of recessive disease development and do not require phasing. Across all diseases, 2.6% of the samples had a potentially damaging CH variant and 16.2% had a potentially damaging HA variant. Of these samples with potentially damaging variants, the average number of genes per sample was 1 with a CH variant and 1.25 with a HA variant. Across all samples, 5.1 genes per disease had a CH variant, while 35.6 genes per disease had a HA variant; on average, only 4.3% of these variants affected common genes. Therefore, when seeking to identify potentially damaging variants of a putatively recessive disease, CH variants should be considered as potential contributors to disease development. If CH variants are excluded from analysis, important candidate genes may be overlooked.

Novel Molecular Hallmarks of Group 3 Medulloblastoma by Single-Cell Transcriptomics

Medulloblastoma (MB) is a highly heterogeneous and one of the most malignant pediatric brain tumors, comprising four subgroups: Sonic Hedgehog, Wingless, Group 3, and Group 4. Group 3 MB has the worst prognosis of all MBs. However, the molecular and cellular mechanisms driving the maintenance of malignancy are poorly understood. Here, we employed high-throughput single-cell and bulk RNA sequencing to identify novel molecular features of Group 3 MB, and found that a specific cell cluster displayed a highly malignant phenotype. Then, we identified the glutamate receptor metabotropic 8 (GRM8), and AP-1 complex subunit sigma-2 (AP1S2) genes as two critical markers of Group 3 MB, corresponding to its poor prognosis. Information on 33 clinical cases was further utilized for validation. Meanwhile, a global map of the molecular cascade downstream of the MYC oncogene in Group 3 MB was also delineated using single-cell RNA sequencing. Our data yields new insights into Group 3 MB molecular characteristics and provides novel therapeutic targets for this relentless disease.

Embryonal tumors of the central nervous system

PURPOSE OF REVIEW

This review aims to give an update on histopathological, molecular and clinical features of central nervous system (CNS) 'embryonal' tumors.

RECENT FINDINGS

The taxonomy of previously called 'CNS primitive neuroectodermal tumor' (CNS PNET) has been deeply modified since the discovery of specific molecular profiles for each various sub-entity of these rare, mainly pediatric, tumors. The term 'embryonal tumors' now refers to medulloblastomas, atypical teratoid rhabdoid tumors (AT/RT) and other rare entities, defined by their specific histopathological features together with expression-based or methylation-based profiling; specific gene mutations or fusions characterize some tumor types. In addition, the compilation of large series of molecular data has allowed to dissecting several of these tumor types in molecular subgroups, increasing the number of tumor entities, and leading to an amazingly complex nosology of rare-to-extremely rare malignancies. This rarity precludes from having strong evidence-based therapeutic recommendations, although international efforts are conducted to define the best treatment strategies.

SUMMARY

Embryonal tumors now correspond to molecularly well defined entities, which deserve further international collaborations to specify their biology and the appropriate burden of treatment, in order to minimize the long-term side-effects of treatment of these overall rare and severe diseases of childhood.

Recent Advances in Understanding the Role of Autophagy in Paediatric Brain Tumours

Autophagy is a degradative process occurring in eukaryotic cells to maintain homeostasis and cell survival. After stressful conditions including nutrient deprivation, hypoxia or drugs administration, autophagy is induced to counteract pathways that could lead to cell death. In cancer, autophagy plays a paradoxical role, acting both as tumour suppressor—by cleaning cells from damaged organelles and inhibiting inflammation or, alternatively, by promoting genomic stability and tumour adaptive response—or as a pro-survival mechanism to protect cells from stresses such as chemotherapy. Neural-derived paediatric solid tumours represent a variety of childhood cancers with unique anatomical location, cellular origins, and clinical presentation. These tumours are a leading cause of morbidity and mortality among children and new molecular diagnostics and therapies are necessary for longer survival and reduced morbidity. Here, we review advances in our understanding of how autophagy modulation exhibits antitumor properties in experimental models of paediatric brain tumours, i.e., medulloblastoma (MB), ependymoma (EPN), paediatric low-grade and high-grade gliomas (LGGs, HGGs), atypical teratoid/rhabdoid tumours (ATRTs), and retinoblastoma (RB). We also discuss clinical perspectives to consider how targeting autophagy may be relevant in these specific paediatric tumours.

Pediatric Brain Tumors: Descriptive Epidemiology, Risk Factors, and Future Directions

Brain tumors are the most common solid tumors in children and remain a significant contributor to death by disease in this population. Pediatric brain tumors (PBT) are broadly classified into two major categories: glial and neuronal tumors. Various factors, including tumor histology, tumor location, and demographics, influence the incidence and prognosis of this heterogeneous group of neoplasms. Numerous epidemiologic studies have been conducted to identify genetic and environmental risk factors for these malignancies. Thus far, the only established risk factors for PBTs are exposure to ionizing radiation and some rare genetic syndromes. However, relatively consistent evidence of positive associations for birth defects, markers of fetal growth, advanced parental age, maternal dietary N-nitroso compounds, and exposure to pesticides have been reported. The genetic variants associated with susceptibility to PBTs were predominantly identified by a candidate-gene approach. The identified genetic variants belong to four main pathways, including xenobiotic detoxification, inflammation, DNA repair, and cell-cycle regulation. Conducting large and multi-institutional studies is warranted to systematically detect genetic and environmental risk factors for different histologic subtypes of PBTs. This, in turn, might lead to a better understanding of etiology of PBTs and eventually developing risk prediction models to prevent these clinically significate malignancies.

Proportion of children with cancer that have an indication for genetic counseling and testing based on the cancer type irrespective of other features

In children with cancer, specific clinical features such as physical anomalies, occurrence of cancer in young relatives, specific cancer histologies, and unique mutation/methylation signatures may indicate the presence of an underlying cancer predisposition syndrome (CPS). The proportion of children with a cancer type suggesting a CPS among all children with cancer is unknown. To determine the proportion of children with cancer types suggesting an underlying CPS among children with cancer. We evaluated the number of children with cancer types strongly associated with CPS diagnosed in Germany between 2007 and 2016. Data were obtained from various sources including two national pediatric pathology reference laboratories for brain and solid tumors, respectively, various childhood cancer trial offices as well as the German Childhood Cancer Registry. Among 21,127 children diagnosed with cancer between 2007 and 2016, 2554 (12.1%) had a cancer type strongly associated with a CPS. The most common diagnoses were myelodysplastic syndrome and juvenile myelomonocytic leukemia, retinoblastoma, malignant peripheral nerve sheath tumor, infantile myofibromatosis, medulloblastoma^SHH, rhabdoid tumor as well as atypical teratoid/rhabdoid tumor. Based on cancer type only, 12.1% of all children with cancer have an indication for a genetic evaluation. Pediatric oncology patients require access to genetic counselling and testing.

Clinical utility of comprehensive genomic profiling in central nervous system tumors of children and young adults

Background

Recent large-scale genomic studies have revealed a spectrum of genetic variants associated with specific subtypes of central nervous system (CNS) tumors. The aim of this study was to determine the clinical utility of comprehensive genomic profiling of pediatric, adolescent and young adult (AYA) CNS tumors in a prospective setting, including detection of DNA sequence variants, gene fusions, copy number alterations (CNAs), and loss of heterozygosity.

Methods

OncoKids, a comprehensive DNA- and RNA-based next-generation sequencing (NGS) panel, in conjunction with chromosomal microarray analysis (CMA) was employed to detect diagnostic, prognostic, and therapeutic markers. NGS was performed on 222 specimens from 212 patients. Clinical CMA data were analyzed in parallel for 66% (146/222) of cases.

Results

NGS demonstrated clinically significant alterations in 66% (147/222) of cases. Diagnostic markers were identified in 62% (138/222) of cases. Prognostic information and targetable genomic alterations were identified in 22% (49/222) and 18% (41/222) of cases, respectively. Diagnostic or prognostic CNAs were revealed by CMA in 69% (101/146) of cases. Importantly, clinically significant CNAs were detected in 57% (34/60) of cases with noncontributory NGS results. Germline cancer predisposition testing was indicated for 27% (57/212) of patients. Follow-up germline testing was performed for 20 patients which confirmed a germline pathogenic/likely pathogenic variant in 9 cases: TP53 (2), NF1 (2), SMARCB1 (1), NF2 (1), MSH6 (1), PMS2 (1), and a patient with 47,XXY Klinefelter syndrome.

Conclusions

Our results demonstrate the significant clinical utility of integrating genomic profiling into routine clinical testing for pediatric and AYA patients with CNS tumors.

Genomic and Transcriptomic Analyses Reveals ZNF124 as a Critical Regulator in Highly Aggressive Medulloblastomas

Medulloblastoma (MB) is the most common malignant pediatric brain tumor, however, the mechanisms underlying tumorigenesis in different MB subgroups remain incompletely understood. Although previous studies of MB predisposition have been conducted in tertiary referral centers primarily in Caucasian cohorts, it is not unclear clear whether there exist population-specific genetic alterations in MBs. In this study, we investigated the contribution of genomic and transcriptomic alterations to the risk of malignant MB in the Chinese population (designated as the Asian cohort). We analyze the genomic and transcriptomic alterations of the Asian MB cohort by using a combination of whole-exome sequencing (WES) and RNA-deep-sequencing. In addition, we integrate publicly available data with the Asian MB cohort and identify a subset of potential MB-driving genes specifically enriched in each of the MB subgroups. We further characterize a newly identified group-3-enriched transcriptional regulator, ZNF124, and demonstrate that ZNF124 is critical for the growth of the most aggressive group-3 MB cells. Together, our analyses indicate conserved yet distinct genetic alterations and gene expression patterns of MBs between different ethnic groups. Our studies further provide an important resource for identifying potential tumor-driving factors in MBs, enhancing our understanding of the disease process for developing ethnically targeted therapies in patients with MB.

Genetic syndromes predisposing to pediatric brain tumors

The application of high-throughput sequencing approaches including paired tumor/normal sampling with therapeutic intent has demonstrated that 8%-19% of pediatric CNS tumor patients harbor a germline alteration in a classical tumor predisposition gene (NF1, P53). In addition, large-scale germline sequencing studies in unselected cohorts of pediatric neuro-oncology patients have demonstrated novel candidate tumor predisposition genes (ELP1 alterations in sonic hedgehog medulloblastoma). Therefore, the possibility of an underlying tumor predisposition syndrome (TPS) should be considered in all pediatric patients diagnosed with a CNS tumor which carries critical implications including accurate prognostication, selection of optimal therapy, screening, risk reduction, and family planning. The Pediatric Cancer Working Group of the American Association for Cancer Research (AACR) recently published consensus screening recommendations for children with the most common TPS. In this review, we provide an overview of the most relevant as well as recently identified TPS associated with the most frequently encountered pediatric CNS tumors with an emphasis on pathogenesis, genetic testing, clinical features, and treatment implications.

Medulloblastomas associated with an APC germline pathogenic variant share the good prognosis of CTNNB1-mutated medulloblastomas

BACKGROUND

Medulloblastomas may occur in a predisposition context, including familial adenomatosis polyposis. Medulloblastomas related to a germline pathogenic variant of adenomatous polyposis coli (APC) remain rare and poorly described. Their similarities with sporadic WNT medulloblastomas still require description.

METHODS

We performed a multicentric retrospective review of 12 patients treated between 1988 and 2018 for medulloblastoma with an identified or highly suspected (personal or familial history) APC germline pathogenic variant. We report personal and familial history APC gene pathogenic variants whenever available: clinical and histologic characteristics of the medulloblastoma, treatments, and long-term outcome, including second tumor and late sequelae.

RESULTS

Medulloblastomas associated with APC pathogenic variants are mainly classic (11/11 patients, 1 not available), nonmetastatic (10/12 patients) medulloblastomas, with nuclear immunoreactivity for ß-catenin (9/9 tested cases). Ten of 11 assessable patients are disease free with a median follow-up of 10.7 years (range, 1-28 y). Secondary tumors included desmoid tumors in 7 patients (9 tumors), 1 thyroid carcinoma, 2 pilomatricomas, 1 osteoma, 1 vertebral hemangioma, and 1 malignant triton in the radiation field, which caused the only cancer-related death in our series.

CONCLUSIONS

Medulloblastomas associated with an APC pathogenic variant have an overall favorable outcome, even for metastatic tumors. Yet, long-term survival is clouded by second tumor occurrence; treatment may play some role in some of these second malignancies. Our findings raise the question of applying a de-escalation therapeutic protocol to treat patients with APC germline pathogenic variants given the excellent outcome, and reduced intensity of craniospinal irradiation may be further evaluated.

Medulloblastoma Associated with Down Syndrome: From a Rare Event Leading to a Pathogenic Hypothesis

Down syndrome (DS) is the most common chromosome abnormality with a unique cancer predisposition syndrome pattern: a higher risk to develop acute leukemia and a lower incidence of solid tumors. In particular, brain tumors are rarely reported in the DS population, and biological behavior and natural history are not well described and identified. We report a case of a 10-year-old child with DS who presented with a medulloblastoma (MB). Histological examination revealed a classic MB with focal anaplasia and the molecular profile showed the presence of a CTNNB1 variant associated with the wingless (WNT) molecular subgroup with a good prognosis in contrast to our case report that has shown an early metastatic relapse. The nearly seven-fold decreased risk of MB in children with DS suggests the presence of protective biological mechanisms. The cerebellum hypoplasia and the reduced volume of cerebellar granule neuron progenitor cells seem to be a possible favorable condition to prevent MB development via inhibition of neuroectodermal differentiation. Moreover, the NOTCH/WNT dysregulation in DS, which is probably associated with an increased risk of leukemia, suggests a pivotal role of this pathway alteration in the pathogenesis of MB; therefore, this condition should be further investigated in future studies by molecular characterizations.

Retrospective investigation of hereditary syndromes in patients with medulloblastoma in a single institution

PURPOSE

To investigate the incidence rate of hereditary disease in patients with medulloblastoma.

METHODS

The genetic reports of 129 patients with medulloblastoma from January 2016 to December 2019 were retrospectively analyzed. A panel sequence of 39 genes (Genetron Health) were used for all patients to evaluate the tumor subgroup. Four genes (TP53, APC, PTCH1, SUFU) were screened to routinely rule out germline mutation.

RESULTS

Five patients (3.9%) were found with hereditary disease, and all belonged to the sonic hedgehog (SHH) subgroup. Two patients were retrospectively diagnosed with Gorlin-Goltz disease with germline PTCH1 and SUFU mutations. One patient (PTCH1 mutation) accepted whole craniospinal irradiation and had scalp nevoid basal cell carcinoma 5 years later. The other patient (SUFU mutation) accepted chemotherapy and had local tumor relapse 1 year later. Three patients were diagnosed with Li-Fraumeni syndrome and carried the TP53 mutation; all three patients died. One of the patients had bone osteosarcoma, while all three had early tumor relapse.

CONCLUSION

Patients with SHH medulloblastoma should routinely undergo genetic testing. We propose that whole genome, whole exome sequence, or custom-designed panel-targeted exome sequencing should be performed.

Predisposition to cancer in children and adolescents

Childhood malignancies are rarely related to known environmental exposures, and it has become increasingly evident that inherited genetic factors play a substantial causal role. Large-scale sequencing studies have shown that approximately 10% of children with cancer have an underlying cancer predisposition syndrome. The number of recognised cancer predisposition syndromes and cancer predisposition genes are constantly growing. Imaging and laboratory technologies are improving, and knowledge of the range of tumours and risk of malignancy associated with cancer predisposition syndromes is increasing over time. Consequently, surveillance measures need to be constantly adjusted to address these new findings. Management recommendations for individuals with pathogenic germline variants in cancer predisposition genes need to be established through international collaborative studies, addressing issues such as genetic counselling, cancer prevention, cancer surveillance, cancer therapy, psychological support, and social-ethical issues. This Review represents the work by a group of experts from the European Society for Paediatric Oncology (SIOPE) and aims to summarise the current knowledge and define future research needs in this evolving field.

Novel PHOX2B germline mutation in childhood medulloblastoma: a case report

BACKGROUND

Medulloblastoma is an aggressive brain tumor mostly found in children, few studies on pathogenic germline mutations predisposing this disease was reported.

CASE PRESENTATION

We present an 11-year-old male with medulloblastoma, who harbors a de novo PHOX2B germline mutation as detected by whole exome sequencing (WES). Family history was negative. Sanger sequencing confirmed this mutation in peripheral blood, hair bulbs, urine and saliva. Identification of novel germline mutations is beneficial for childhood cancer screening.

CONCLUSIONS

This case revealed a de novo PHOX2B germline mutation as a potential cause of medulloblastoma in a child and suggests familial germline variant screening is useful when an affected family is considering having a second child.

Clinical and genetic profiling of nevoid basal cell carcinoma syndrome in Korean patients by whole-exome sequencing

Nevoid basal cell carcinoma syndrome (NBCCS) is mainly characterised by multiple basal cell carcinomas (BCCs) caused by PTCH1, PTCH2, and SUFU. However, clinical and genetic data on Asian NBCCS patients are limited. We aimed to analyse the clinical phenotypes and genetic spectrum of Korean patients with NBCCS. Fifteen patients with NBCCS at Seoul National University Hospital were included, and their clinical data were analysed. Whole-exome sequencing and/or multiplex ligation-dependent probe amplification using peripheral blood were performed to identify genetic causes. Genetic analysis revealed that 73.3% (11/15) of the patients carried 9 pathogenic variants, only in the PTCH1 gene. Variants of uncertain significance (VUS) and likely benign were also detected in 2 (13.3%) and 2 (13.3%) patients, respectively. BCCs were found in the majority of the cases (93.3%) and the number of BCCs increased with age (ρ = 0.595, P = 0.019). This study revealed that PTCH1 pathogenic variants were the main cause of NBCCS in Korean patients. As BCCs are commonly detected, a periodic dermatologic examination is recommended. Finally, our results support the addition of genetic screening to the existing criteria for NBCCS diagnosis.

Frequency of Pathogenic Germline Variants in Cancer-Susceptibility Genes in Patients With Osteosarcoma

Importance

Osteosarcoma, the most common malignant bone tumor in children and adolescents, occurs in a high number of cancer predisposition syndromes that are defined by highly penetrant germline mutations. The germline genetic susceptibility to osteosarcoma outside of familial cancer syndromes remains unclear.

Objective

To investigate the germline genetic architecture of 1244 patients with osteosarcoma.

Design, Setting, and Participants

Whole-exome sequencing (n = 1104) or targeted sequencing (n = 140) of the DNA of 1244 patients with osteosarcoma from 10 participating international centers or studies was conducted from April 21, 2014, to September 1, 2017. The results were compared with the DNA of 1062 individuals without cancer assembled internally from 4 participating studies who underwent comparable whole-exome sequencing and 27 173 individuals of non-Finnish European ancestry who were identified through the Exome Aggregation Consortium (ExAC) database. In the analysis, 238 high-interest cancer-susceptibility genes were assessed followed by testing of the mutational burden across 736 additional candidate genes. Principal component analyses were used to identify 732 European patients with osteosarcoma and 994 European individuals without cancer, with outliers removed for patient-control group comparisons. Patients were subsequently compared with individuals in the ExAC group. All data were analyzed from June 1, 2017, to July 1, 2019.

Main Outcomes and Measures

The frequency of rare pathogenic or likely pathogenic genetic variants.

Results

Among 1244 patients with osteosarcoma (mean [SD] age at diagnosis, 16 [8.9] years [range, 2-80 years]; 684 patients [55.0%] were male), an analysis restricted to individuals with European ancestry indicated a significantly higher pathogenic or likely pathogenic variant burden in 238 high-interest cancer-susceptibility genes among patients with osteosarcoma compared with the control group (732 vs 994, respectively; P = 1.3 × 10-18). A pathogenic or likely pathogenic cancer-susceptibility gene variant was identified in 281 of 1004 patients with osteosarcoma (28.0%), of which nearly three-quarters had a variant that mapped to an autosomal-dominant gene or a known osteosarcoma-associated cancer predisposition syndrome gene. The frequency of a pathogenic or likely pathogenic cancer-susceptibility gene variant was 128 of 1062 individuals (12.1%) in the control group and 2527 of 27 173 individuals (9.3%) in the ExAC group. A higher than expected frequency of pathogenic or likely pathogenic variants was observed in genes not previously linked to osteosarcoma (eg, CDKN2A, MEN1, VHL, POT1, APC, MSH2, and ATRX) and in the Li-Fraumeni syndrome-associated gene, TP53.

Conclusions and Relevance

In this study, approximately one-fourth of patients with osteosarcoma unselected for family history had a highly penetrant germline mutation requiring additional follow-up analysis and possible genetic counseling with cascade testing.

Neurooncology: 2021 update

This article briefly presents 10 topics that were selected by the author as 'top 10 discoveries' published in 2020 in the broader field of neurooncological pathology including neurosciences as well as clinical neurooncology of interest for neurooncological pathology. The selected topics concern new information on the molecular characteristics of gliomas (infratentorial IDH-mutant diffuse astrocytomas, pediatric low-grade gliomas, infant-type high-grade gliomas, hypermutation in gliomas), the immunological aspects of the brain tumor microenvironment (TME), the impact of the TME on preclinical glioma models, and the importance of lymphatic drainage on brain tumor surveillance. Furthermore, important papers were published on two 'new' genetic syndromes predisposing to medulloblastoma, on liquid biopsy-based diagnosis of central nervous system (CNS) tumors, and on the 'microbiome' in glioblastomas (and other cancers). In the last part of this review, a dozen of papers are given as examples of papers that did not make it to the top 10 list of the author, underscoring the subjective component in the selection process. Acknowledging that 2020 will be remembered as the year in which the world changed because of the COVID-19 pandemic, some of the consequences of this pandemic for neurooncological pathology are briefly discussed as well. Hopefully, this review forms an incentive to appreciate the wealth of information provided by the papers that were used as building blocks for the present manuscript.

Canadian Pediatric Neuro-Oncology Standards of Practice

Primary CNS tumors are the leading cause of cancer-related death in pediatrics. It is essential to understand treatment trends to interpret national survival data. In Canada, children with CNS tumors are treated at one of 16 tertiary care centers. We surveyed pediatric neuro-oncologists to create a national standard of practice to be used in the absence of a clinical trial for seven of the most prevalent brain tumors in children. This allowed description of practice across the country, along with a consensus. This had a multitude of benefits, including understanding practice patterns, allowing for a basis to compare in future research and informing Health Canada of the current management of patients. This also allows all children in Canada to receive equivalent care, regardless of location.

Nationwide germline whole genome sequencing of 198 consecutive pediatric cancer patients reveals a high incidence of cancer prone syndromes

PURPOSE

Historically, cancer predisposition syndromes (CPSs) were rarely established for children with cancer. This nationwide, population-based study investigated how frequently children with cancer had or were likely to have a CPS.

METHODS

Children (0-17 years) in Denmark with newly diagnosed cancer were invited to participate in whole-genome sequencing of germline DNA. Suspicion of CPS was assessed according to Jongmans'/McGill Interactive Pediatric OncoGenetic Guidelines (MIPOGG) criteria and familial cancer diagnoses were verified using population-based registries.

RESULTS

198 of 235 (84.3%) eligible patients participated, of whom 94/198 (47.5%) carried pathogenic variants (PVs) in a CPS gene or had clinical features indicating CPS. Twenty-nine of 198 (14.6%) patients harbored a CPS, of whom 21/198 (10.6%) harbored a childhood-onset and 9/198 (4.5%) an adult-onset CPS. In addition, 23/198 (11.6%) patients carried a PV associated with biallelic CPS. Seven of the 54 (12.9%) patients carried two or more variants in different CPS genes. Seventy of 198 (35.4%) patients fulfilled the Jongmans' and/or MIPOGG criteria indicating an underlying CPS, including two of the 9 (22.2%) patients with an adult-onset CPS versus 18 of the 21 (85.7%) patients with a childhood-onset CPS (p = 0.0022), eight of the additional 23 (34.8%) patients with a heterozygous PV associated with biallelic CPS, and 42 patients without PVs. Children with a central nervous system (CNS) tumor had family members with CNS tumors more frequently than patients with other cancers (11/44, p = 0.04), but 42 of 44 (95.5%) cases did not have a PV in a CPS gene.

CONCLUSION

These results demonstrate the value of systematically screening pediatric cancer patients for CPSs and indicate that a higher proportion of childhood cancers may be linked to predisposing germline variants than previously supposed.

An Immune-Related Signature for Predicting the Prognosis of Lower-Grade Gliomas

Background

Lower-grade gliomas (LGGs) have more favorable outcomes than glioblastomas; however, LGGs often progress to process glioblastomas within a few years. Numerous studies have proven that the tumor microenvironment (TME) is correlated with the prognosis of glioma.

Methods

LGG RNA-Sequencing (RNA-seq) data from The Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA) were extracted and then divided into training and testing cohorts, respectively. Immune-related differentially expressed genes (DEGs) were screened to establish a prognostic signature by a multivariate Cox proportional hazards regression model. The immune-related risk score and clinical information, such as age, sex, World Health Organization (WHO) grade, and isocitrate dehydrogenase 1 (IDH1) mutation, were used to independently validate and develop a prognostic nomogram. GO and KEGG pathway analyses to DEGs between immune-related high-risk and low-risk groups were performed.

Results

Sixteen immune-related genes were screened for establishing a prognostic signature. The risk score had a negative correlation with prognosis, with an area under the receiver operating characteristic (ROC) curve of 0.941. The risk score, age, grade, and IDH1 mutation were identified as independent prognostic factors in patients with LGGs. The hazard ratios (HRs) of the high-risk score were 5.247 [95% confidence interval (CI) = 3.060–8.996] in the multivariate analysis. A prognostic nomogram of 1-, 3-, and 5-year survival was established and validated internally and externally. Go and KEGG pathway analyses implied that immune-related biological function and pathways were involved in the TME.

Conclusion

The immune-related prognostic signature and the prognostic nomogram could accurately predict survival.

Deconstructing Sonic Hedgehog Medulloblastoma: Molecular Subtypes, Drivers, and Beyond

Medulloblastoma (MB) is a highly malignant cerebellar tumor predominantly diagnosed during childhood. Driven by pathogenic activation of sonic hedgehog (SHH) signaling, SHH subgroup MB (SHH-MB) accounts for nearly one-third of diagnoses. Extensive molecular analyses have identified biologically and clinically relevant intertumoral heterogeneity among SHH-MB tumors, prompting the recognition of novel subtypes. Beyond germline and somatic mutations promoting constitutive SHH signaling, driver alterations affect a multitude of pathways and molecular processes, including TP53 signaling, chromatin modulation, and post-transcriptional gene regulation. Here, we review recent advances in the underpinnings of SHH-MB in the context of molecular subtypes, clarify novel somatic and germline drivers, highlight cellular origins and developmental hierarchies, and describe the composition of the tumor microenvironment and its putative role in tumorigenesis.

XPC deficiency increases risk of hematologic malignancies through mutator phenotype and characteristic mutational signature

Recent studies demonstrated a dramatically increased risk of leukemia in patients with a rare genetic disorder, Xeroderma Pigmentosum group C (XP-C), characterized by constitutive deficiency of global genome nucleotide excision repair (GG-NER). The genetic mechanisms of non-skin cancers in XP-C patients remain unexplored. In this study, we analyze a unique collection of internal XP-C tumor genomes including 6 leukemias and 2 sarcomas. We observe a specific mutational pattern and an average of 25-fold increase of mutation rates in XP-C versus sporadic leukemia which we presume leads to its elevated incidence and early appearance. We describe a strong mutational asymmetry with respect to transcription and the direction of replication in XP-C tumors suggesting association of mutagenesis with bulky purine DNA lesions of probably endogenous origin. These findings suggest existence of a balance between formation and repair of bulky DNA lesions by GG-NER in human body cells which is disrupted in XP-C patients.

Xeroderma Pigmentosum group C (XP-C) is a rare genetic disorder characterised by deficient DNA repair leading to skin and internal cancer, but the latter is not well understood molecularly. Here the authors sequence genomes of non-skin cancers from XP-C patients to unravel its mutational patterns.

Medulloblastoma: "Onset of the molecular era"

Among brain tumors, Medulloblastoma (MB) is one of the most common, malignant, pediatric tumors of the cerebellum. It accounts for ~20% of all childhood central nervous system (CNS) tumors. Despite, tremendous advances in drug development processes, as well as novel drugs for MB the morbidity and mortality rates, remain high. Craniospinal radiation, high-dose chemotherapy, and surgical resection are the primary therapeutic strategies. Tremendous progress in the field of "genomics" with vast amounts of data has led to the identification of four distinct molecular subgroups in medulloblastoma: WNT group, SHH group, group-III, and group-IV. The identification of these subgroups has led to individualized treatment strategies for each subgroup. Here, we discuss the various molecular subgroups of medulloblastoma as well as the differences between them. We also highlight the latest treatment strategies available for medulloblastoma.

Molecular stratifications, biomarker candidates and new therapeutic options in current medulloblastoma treatment approaches

Medulloblastoma (MB) is the most common malignant childhood tumor of the brain. Multimodal treatment consisting of surgery, radiation therapy, and chemotherapy reduced cumulative incidence of late mortality but increased the incidence of subsequent neoplasms and severe, incapacitating chronic health conditions. Present treatment strategies fail to recognize heterogeneity within patients despite wide divergence in individual responses. The persistent mortality rates and serious side effects of non-targeted cytotoxic therapies indicate a need for more refined therapeutic approaches. Advanced genomic research has led to the accumulation of an enormous amount of genetic information and resulted in a consensus distinguishing four molecular subgroups, WNT-activated, SHH-activated, and Group 3 and 4 medulloblastomas. These have distinct origin, demographics, molecular alterations, and clinical outcomes. Although subgroup affiliation does not predict response to therapy, new subgroup-specific markers of prognosis can enable a more layered risk stratification with additional subtypes within each primary subgroup. Here, we summarize subgroup-specific genetic alterations and their utility in current treatment strategies. The transition toward molecularly targeted interventions for newly diagnosed MBs remains slow, and prospective trials are needed to confirm stratifications based on molecular alterations. At the same time, numerous studies focus at fine-tuning the intensity of invasive radio- and chemotherapies to reduce intervention-related long-term morbidity. There are an increasing number of immunotherapy-based treatment strategies including immune checkpoint-inhibitors, oncolytic viruses, CAR-T therapy, and NK cells in recurrent and refractory MBs. Although most trials are in early phase, there is hope for therapeutic breakthroughs for advanced MBs within the next decade.

Cancer Predisposition Syndromes and Medulloblastoma in the Molecular Era

Medulloblastoma is the most common malignant brain tumor in children. In addition to sporadic cases, medulloblastoma may occur in association with cancer predisposition syndromes. This review aims to provide a complete description of inherited cancer syndromes associated with medulloblastoma. We examine their epidemiological, clinical, genetic, and diagnostic features and therapeutic approaches, including their correlation with medulloblastoma. Furthermore, according to the most recent molecular advances, we describe the association between the various molecular subgroups of medulloblastoma and each cancer predisposition syndrome. Knowledge of the aforementioned conditions can guide pediatric oncologists in performing adequate cancer surveillance. This will allow clinicians to promptly diagnose and treat medulloblastoma in syndromic children, forming a team with all specialists necessary for the correct management of the other various manifestations/symptoms related to the inherited cancer syndromes.

Genetic Predisposition to Solid Pediatric Cancers

Progresses over the past years have extensively improved our capacity to use genome-scale analyses—including high-density genotyping and exome and genome sequencing—to identify the genetic basis of pediatric tumors. In particular, exome sequencing has contributed to the evidence that about 10% of children and adolescents with tumors have germline genetic variants associated with cancer predisposition. In this review, we provide an overview of genetic variations predisposing to solid pediatric tumors (medulloblastoma, ependymoma, astrocytoma, neuroblastoma, retinoblastoma, Wilms tumor, osteosarcoma, rhabdomyosarcoma, and Ewing sarcoma) and outline the biological processes affected by the involved mutated genes. A careful description of the genetic basis underlying a large number of syndromes associated with an increased risk of pediatric cancer is also reported. We place particular emphasis on the emerging view that interactions between germline and somatic alterations are a key determinant of cancer development. We propose future research directions, which focus on the biological function of pediatric risk alleles and on the potential links between the germline genome and somatic changes. Finally, the importance of developing new molecular diagnostic tests including all the identified risk germline mutations and of considering the genetic predisposition in screening tests and novel therapies is emphasized.

Circulating tumour DNA from the cerebrospinal fluid allows the characterisation and monitoring of medulloblastoma

The molecular characterisation of medulloblastoma, the most common paediatric brain tumour, is crucial for the correct management and treatment of this heterogenous disease. However, insufficient tissue sample, the presence of tumour heterogeneity, or disseminated disease can challenge its diagnosis and monitoring. Here, we report that the cerebrospinal fluid (CSF) circulating tumour DNA (ctDNA) recapitulates the genomic alterations of the tumour and facilitates subgrouping and risk stratification, providing valuable information about diagnosis and prognosis. CSF ctDNA also characterises the intra-tumour genomic heterogeneity identifying small subclones. ctDNA is abundant in the CSF but barely present in plasma and longitudinal analysis of CSF ctDNA allows the study of minimal residual disease, genomic evolution and the characterisation of tumours at recurrence. Ultimately, CSF ctDNA analysis could facilitate the clinical management of medulloblastoma patients and help the design of tailored therapeutic strategies, increasing treatment efficacy while reducing excessive treatment to prevent long-term secondary effects.

Identification of a Twelve-Gene Signature and Establishment of a Prognostic Nomogram Predicting Overall Survival for Medulloblastoma

BACKGROUND

Medulloblastoma is the common pediatric malignant tumor with poor prognosis in cerebellum. However, MB is always with clinical heterogeneity. To provide patients with more clinically beneficial treatment strategies, there is a pressing need to develop a new prognostic prediction model as a supplement to the prediction outcomes of clinical judgment.

MATERIALS AND METHODS

Four datasets of mRNA expression and clinical data were downloaded from gene expression omnibus (GEO) database. Differentially expressed genes (DEGs) were identified and functionally enriched among GSE50161, GSE74195, GSE86574. Then we used STRING and Cytoscape to constructed and analyze protein-protein interaction network (PPI) and hub genes. Univariate cox regression analysis was performed to identify overall survival-related hub genes in an unique dataset from GSE85217 as train cohort. Lasso Cox regression model was used to construct the prognostic gene signature. Time-dependent receiver operating characteristic (ROC), Kaplan-Meier curve, univariate and multivariate Cox regression analysis were used to assess the prognostic capacity of the twelve-gene signature. A unique dataset from GSE85217 was downloaded to further validate the results. Finally, we established the nomogram by using the gene signature and validated it with ROC curve. Gene set enrichment analysis (GSEA) was carried out to further investigate its potential molecular mechanism. Besides, the twelve genes expression at the mRNA and protein levels was validated using external database such as Oncomine, cBioportal and HPA, respectively.

RESULTS

A twelve-gene signature comprising FOXM1, NEK2, CCT2, ACTL6A, EIF4A3, CCND2, ABL1, SYNCRIP, ITGB1, NRXN2, ENAH, and UMPS was established to predict overall survival of medulloblastoma. The ROC curve showed good performance in survival prediction in both the train cohort and the validation cohort. The twelve-gene signature could stratify patients into a high risk and low risk group which had significantly different survival. Univariate and multivariate Cox regression revealed that the twelve-gene signature was an independent prognostic factor in medulloblastoma. Nomogram, which included twelve-gene signatures, was established and showed some clinical benefit.

CONCLUSION

Our study identified a twelve-gene signature and established a prognostic nomogram that reliably predicts overall survival in medulloblastoma. The above results will help us to better analyze the pathogenesis and treatment of medulloblastoma in the future.

Parental attitudes regarding the need for genetic services in a pediatric brain tumor survivorship program

Pediatric brain tumor survivorship populations have not been typically offered genetic services as part of routine care. Genetic services can be defined as family history collection, genetic risk assessment for a patient and family members, and coordination of genetic testing. Prior research has focused on the integration of genetic services in the general pediatric oncology survivorship population and found a need for these services to be implemented. Gathering a family history and providing a genetic risk assessment have previously been determined to be an integral step in determining if an individual's cancer was due to a hereditary predisposition. The purpose of this study was to examine parental attitudes regarding the need for genetic services in their child's pediatric brain tumor survivorship clinic. Twelve semi-structured interviews were conducted with parents participating in the Brain STAR (Survivors Taking Action and Responsibility) program at Ann and Robert H. Lurie Children's Hospital of Chicago. A grounded theory approach was used to code and analyze the results thematically. Five key themes were identified: participants' perceived benefits and barriers regarding receiving genetic services, desirable time for implementation of these services, relevance of family history, and their thoughts regarding reproductive risk. These results provide insight for genetics professionals regarding the need for genetic services in this population, and how to best implement them.

Engineered biomimetic nanoparticle for dual targeting of the cancer stem-like cell population in sonic hedgehog medulloblastoma

The sonic hedgehog subtype of medulloblastoma (SHH MB) is associated with treatment failure and poor outcome. Current strategies utilizing whole brain radiation therapy result in deleterious off-target effects on the normal developing childhood brain. Most conventional chemotherapies remain limited by ineffective blood-brain barrier (BBB) penetrance. These challenges signify an unmet need for drug carriers that can cross the BBB and deliver drugs to targeted sites with high drug-loading efficiency and long-term stability. We herein leverage the enhanced stability and targeting ability of engineered high-density lipoprotein-mimetic nanoparticles (eHNPs) to cross the BBB and deliver a SHH inhibitor effectively to the cancer stem-like cell population in SHH MB. Our microfluidic technology enabled highly reproducible production of multicomponent eHNPs incorporated with apolipoprotein A1, anti-CD15, and a SHH inhibitor (LDE225). We demonstrate the dual-targeted delivery and enhanced therapeutic effect of eHNP-A1-CD15-LDE225 via scavenger receptor class B type 1 (SR-B1) and CD15 on brain SHH MB cells in vitro, ex vivo, and in vivo. Moreover, we show that eHNP-A1 not only serves as a stable drug carrier, but also has a therapeutic effect itself through SR-B1-mediated intracellular cholesterol depletion in SHH MB cells. Through the facilitated and targeted cellular uptake of drugs and direct therapeutic role of this engineered biomimetic nanocarrier in SHH MB, our multifunctional nanoparticle provides intriguing therapeutic promise as an effective and potent nanomedicine for the treatment of SHH MB.

AsiDNA Is a Radiosensitizer with no Added Toxicity in Medulloblastoma Pediatric Models

PURPOSE

Medulloblastoma is an important cause of mortality and morbidity in pediatric oncology. Here, we investigated whether the DNA repair inhibitor, AsiDNA, could help address a significant unmet clinical need in medulloblastoma care, by improving radiotherapy efficacy without increasing radiation-associated toxicity.

EXPERIMENTAL DESIGN

To evaluate the brain permeability of AsiDNA upon systemic delivery, we intraperitoneally injected a fluorescence form of AsiDNA in models harboring brain tumors and in models still in development. Studies evaluated toxicity associated with combination of AsiDNA with radiation in the treatment of young developing animals at subacute levels, related to growth and development, and at chronic levels, related to brain organization and cognitive skills. Efficacy of the combination of AsiDNA with radiation was tested in two different preclinical xenografted models of high-risk medulloblastoma and in a panel of medulloblastoma cell lines from different molecular subgroups and TP53 status. Role of TP53 on the AsiDNA-mediated radiosensitization was analyzed by RNA-sequencing, DNA repair recruitment, and cell death assays.

RESULTS

Capable of penetrating young brain tissues, AsiDNA showed no added toxicity to radiation. Combination of AsiDNA with radiotherapy improved the survival of animal models more efficiently than increasing radiation doses. Medulloblastoma radiosensitization by AsiDNA was not restricted to a specific molecular group or status of TP53. Molecular mechanisms of AsiDNA, previously observed in adult malignancies, were conserved in pediatric models and resembled dose increase when combined with irradiation.

CONCLUSIONS

Our results suggest that AsiDNA is an attractive candidate to improve radiotherapy in medulloblastoma, with no indication of additional toxicity in developing brain tissues.

Pre- and Post-Zygotic TP53 De Novo Mutations in SHH-Medulloblastoma

Simple Summary

Medulloblastoma is the most common malignant brain tumor in children. In a subset of cases, a causal factor is a constitutive mutation of the TP53 gene, which may be inherited or arise for the first time in a patient (de novo). Using an immunohistochemistry assay as a screening tool, we selected patients suspected of harboring a TP53 mutation and offered genetic counseling and germline testing. Our study, which was the first to investigate the parental origin of TP53 mutations in medulloblastoma, allowed the identification of two additional cases with de novo mutations. Moreover, we demonstrated that in one patient the mutation originated at a post-zygotic stage, resulting in somatic mosaicism. These findings have important implications for genetic counseling since they highlight the occurrence of both pre- and post-zygotic TP53 de novo mutations in medulloblastoma, pointing out that in a specific subgroup of patients genetic testing should be offered regardless of family history.

Abstract

Li-Fraumeni syndrome (LFS) is an autosomal dominant disorder caused by mutations in the TP53 gene, predisposing to a wide spectrum of early-onset cancers, including brain tumors. In medulloblastoma patients, the role of TP53 has been extensively investigated, though the prevalence of de novo mutations has not been addressed. We characterized TP53 mutations in a monocentric cohort of consecutive Sonic Hedgehog (SHH)-activated medulloblastoma patients. Germline testing was offered based on tumor p53 immunostaining positivity. Among 24 patients, three (12.5%) showed tumor p53 overexpression, of whom two consented to undergo germline testing and resulted as carriers of TP53 mutations. In the first case, family history was uneventful and the mutation was not found in either of the parents. The second patient, with a family history suggestive of LFS, unexpectedly resulted as a carrier of the mosaic mutation c.742=/C>T p.(Arg248=/Trp). The allele frequency was 26% in normal tissues and 42–77% in tumor specimens. Loss of heterozygosity (LOH) in the tumor was also confirmed. Notably, the mosaic case has been in complete remission for more than one year, while the first patient, as most TP53-mutated medulloblastoma cases from other cohorts, showed a severe and rapidly progressive disease. Our study reported the first TP53 mosaic mutation in medulloblastoma patients and confirmed the importance of germline testing in p53 overexpressed SHH-medulloblastoma, regardless of family history.

Subsequent Neoplasm Risk Associated With Rare Variants in DNA Damage Response and Clinical Radiation Sensitivity Syndrome Genes in the Childhood Cancer Survivor Study

PURPOSE

Radiotherapy for childhood cancer is associated with elevated subsequent neoplasm (SN) risk, but the contribution of rare variants in DNA damage response and radiation sensitivity genes to SN risk is unknown.

PATIENTS AND METHODS

We conducted whole-exome sequencing in a cohort of childhood cancer survivors originally diagnosed during 1970 to 1986 (mean follow-up, 32.7 years), with reconstruction of doses to body regions from radiotherapy records. We identified patients who developed SN types previously reported to be related to radiotherapy (RT-SNs; eg, basal cell carcinoma [BCC], breast cancer, meningioma, thyroid cancer, sarcoma) and matched controls (sex, childhood cancer type/diagnosis, age, SN location, radiation dose, survival). Conditional logistic regression assessed SN risk associated with potentially protein-damaging rare variants (SnpEff, ClinVar) in 476 DNA damage response or radiation sensitivity genes with exact permutation-based P values using a Bonferroni-corrected significance threshold of P < 8.06 × 10-5.

RESULTS

Among 5,105 childhood cancer survivors of European descent, 1,108 (21.7%) developed at least 1 RT-SN. Out-of-field RT-SN risk, excluding BCC, was associated with homologous recombination repair (HRR) gene variants (patient cases, 23.2%; controls, 10.8%; odds ratio [OR], 2.6; 95% CI, 1.7 to 3.9; P = 4.79 × 10-5), most notably but nonsignificantly for FANCM (patient cases, 4.0%; matched controls, 0.6%; P = 9.64 × 10-5). HRR variants were not associated with likely in/near-field RT-SNs, excluding BCC (patient cases, 12.7%; matched controls, 12.9%; P = .92). Irrespective of radiation dose, risk for RT-SNs was also associated with EXO1 variants (patient cases, 1.8%; controls, 0.4%; P = 3.31 × 10-5), another gene implicated in DNA double-strand break repair.

CONCLUSION

In this large-scale discovery study, we identified novel associations between RT-SN risk after childhood cancer and potentially protein-damaging rare variants in genes involved in DNA double-strand break repair, particularly HRR. With replication, these results could affect screening recommendations for childhood cancer survivors and risk-benefit assessments of treatment approaches.

Increased Cancer Risk in Families with Pediatric Cancer Is Associated with Gender, Age, Diagnosis, and Degree of Relation to the Child

BACKGROUND

Studies of cancer risk among relatives of children with cancer beyond parents and siblings are limited. We have investigated the cancer risk up to the third degree of relation in families with pediatric cancer to reveal patterns of inheritance.

METHODS

A single-center cohort of 757 patients with pediatric cancer was linked to the Swedish National Population Register, resulting in 16,137 relatives up to the third degree of relation. All relatives were matched to the Swedish Cancer Register, and standard incidence ratios (SIR) were calculated to define relatives at risk.

RESULTS

Children and adults up to the third degree of relation had increased cancer risk, with SIRs of 1.48 (P = 0.01) and 1.07 (P < 0.01), respectively. The SIRs for first- and third-degree adult relatives were 1.22 and 1.10, respectively, but no increased risk was observed in second-degree relatives. Male relatives had a higher risk than females, especially when related to a girl and when the child had leukemia. The risk was mainly increased for lung, prostate, and gastrointestinal cancer. When excluding 29 families of children with known pathogenic germline variants, the increased risk remained.

CONCLUSIONS

Relatives to children with cancer up to third degree of relation have an increased cancer risk. Known pathogenic germline variants do not explain this increased risk.

IMPACT

The overall increased cancer risk among relatives of children with cancer in this population-based cohort strengthens the importance of surveillance programs for families with pediatric cancer.

Modeling SHH-driven medulloblastoma with patient iPS cell-derived neural stem cells

Here we describe and utilize a model of medulloblastoma, a malignancy accounting for 20% of all childhood brain cancers. We used iPS-derived neural stem cells with a familial mutation causing aberrant SHH signaling. We show that these cells, when transplanted into mouse cerebellum, form tumors that mimics SHH-driven medulloblastoma, demonstrating the development of cancer from healthy neural stem cells in vivo. Our results show that reprogramming of somatic cells carrying familial cancer mutations can be used to model the initiation and progression of childhood cancer.

Medulloblastoma is the most common malignant brain tumor in children. Here we describe a medulloblastoma model using Induced pluripotent stem (iPS) cell-derived human neuroepithelial stem (NES) cells generated from a Gorlin syndrome patient carrying a germline mutation in the sonic hedgehog (SHH) receptor PTCH1. We found that Gorlin NES cells formed tumors in mouse cerebellum mimicking human medulloblastoma. Retransplantation of tumor-isolated NES (tNES) cells resulted in accelerated tumor formation, cells with reduced growth factor dependency, enhanced neurosphere formation in vitro, and increased sensitivity to Vismodegib. Using our model, we identified LGALS1 to be a GLI target gene that is up-regulated in both Gorlin tNES cells and SHH-subgroup of medulloblastoma patients. Taken together, we demonstrate that NES cells derived from Gorlin patients can be used as a resource to model medulloblastoma initiation and progression and to identify putative targets.

Medulloblastoma: an Old Diagnosis with New Promises

PURPOSE OF REVIEW

Molecular subtyping in medulloblastoma (MB) has diagnostic and prognostic values which impact therapy. This paper provides guidance for the clinician caring for pediatric and adult patients with medulloblastoma in the modern era.

RECENT FINDINGS

Medulloblastoma comprises four molecularly distinct subgroups: wingless activated (WNT), sonic hedgehog activated (SHH), group 3, and group 4. Risk stratification before and after the discovery of molecular subgroups aims at minimizing toxicity by reducing radiation and chemotherapy doses in low-risk patients while maintaining favorable overall survival (OS). The mainstay of newly diagnosed medulloblastoma treatment is surgery, radiation therapy, and chemotherapy, except for children under 6 years of age, where high-dose chemotherapy with autologous stem cell rescue is used to avoid or delay radiotherapy, preventing neurocognitive sequelae. Management of recurrent/refractory medulloblastoma remains a challenge with immunotherapy and small-molecule inhibitors forming the backbone of novel strategies. Recent innovations in medulloblastoma research allow us to better understand pathogenesis and molecular characteristics resulting in advanced risk stratification models, new therapeutic approaches, and overall improved survival and quality of life.

Challenges in the Diagnosis of Medulloblastoma Recurrence at an Unusual Site in a Patient With Prader-Willi Syndrome

Medulloblastoma is the most common malignant pediatric brain tumor. Survival rates range between 50% and 80% depending on histology and other biologic features, metastases, and treatment approach. Prader-Willi syndrome (PWS) is a genetically inherited disorder characterized by dysmorphic features, mental retardation, obesity, and hypogonadism among other features. We describe a 10.5-year-old girl with PWS and previous standard-risk medulloblastoma that relapsed in the pons 3 years after the end of treatment. Diagnosis of relapse was delayed by a preceding varicella infection, an initial clinical/radiologic response to steroids and the unusual location, and was confirmed with a stereotactic biopsy. Second-line therapy was commenced, however, the patient rapidly deteriorated and died. This is the first report of medulloblastoma in a patient with PWS.

Why do young people get cancer?

Oncologists and cancer biologists are frequently confronted by the question of what causes cancer? This is particularly vexing for cancers affecting children and young adults who have had limited exposure to environmental mutagens and the effects of aging. Here, I focus on a general framework of the causes of early-onset cancer development in children and young adults by relating inherited and constitutional cancer predisposition, oncogenic pathogens, and developmental mutations. This framework has implications not only for mechanistic investigation of young cancers, but should also clarify improved strategies for their treatment, screening, and potential prevention.

How I Treat Medulloblastoma in Children

Medulloblastoma (MB) is the most common malignant tumor of the central nervous system in children with up to a third of these tumors presenting in children under 3 years of age. Its exquisite radio and chemosensitivity renders high cure rates in children in whom optimal resection has been achieved. Optimal surgery followed by radiation alone can cure about half of these children. The addition of chemotherapy has improved the outcomes dramatically and over 70% of children over 3 years of age with optimal resection and no metastasis can expect to be cured. Increasingly, the focus is on limiting the long-term sequelae of treatment. Precise molecular characterization can enable us to identify patients who can achieve optimal outcomes even in the absence of radiation. Insights into disease biology and molecular characterization have led to dramatic changes in our understanding, risk stratification, prognostication, and treatment approach in these children. In India, there is limited access to molecular profiling, making it challenging to apply biology driven approach to treatment in each child with MB. The Indian Society of Neuro-Oncology guidelines and the SIOP PODC adapted treatment recommendations for standard-risk MB based on the current evidence and logistic realities of low-middle income countries are a useful adjunct to guide clinical practice on a day-to-day basis in our setting.

Germline genetic landscape of pediatric central nervous system tumors

Central nervous system (CNS) tumors are the second most common type of cancer among children. Depending on histopathology, anatomic location, and genomic factors, specific subgroups of brain tumors have some of the highest cancer-related mortality rates or result in considerable lifelong morbidity. Pediatric CNS tumors often occur in patients with genetic predisposition, at times revealing underlying cancer predisposition syndromes. Advances in next-generation sequencing (NGS) have resulted in the identification of an increasing number of cancer predisposition genes. In this review, the literature on genetic predisposition to pediatric CNS tumors is evaluated with a discussion of potential future targets for NGS and clinical implications. Furthermore, we explore potential strategies for enhancing the understanding of genetic predisposition of pediatric CNS tumors, including evaluation of non-European populations, pan-genomic approaches, and large collaborative studies.

EANO-EURACAN clinical practice guideline for diagnosis, treatment, and follow-up of post-pubertal and adult patients with medulloblastoma

The European Association of Neuro-Oncology (EANO) and EUropean RAre CANcer (EURACAN) guideline provides recommendations for the diagnosis, treatment, and follow-up of post-pubertal and adult patients with medulloblastoma. The guideline is based on the 2016 WHO classification of tumours of the CNS and on scientific developments published since 1980. It aims to provide direction for diagnostic and management decisions, and for limiting unnecessary treatments and cost. In view of the scarcity of data in adults with medulloblastoma, we base our recommendations on adult data when possible, but also include recommendations derived from paediatric data if justified. Our recommendations are a resource for professionals involved in the management of post-pubertal and adult patients with medulloblastoma, for patients and caregivers, and for health-care providers in Europe. The implementation of this guideline requires multidisciplinary structures of care, and defined processes of diagnosis and treatment.

Molecular subgrouping of medulloblastoma based on few-shot learning of multitasking using conventional MR images: a retrospective multicenter study

Background

The determination of molecular subgroups—wingless (WNT), sonic hedgehog (SHH), Group 3, and Group 4—of medulloblastomas is very important for prognostication and risk-adaptive treatment strategies. Due to the rare disease characteristics of medulloblastoma, we designed a unique multitask framework for the few-shot scenario to achieve noninvasive molecular subgrouping with high accuracy.

Methods

We introduced a multitask technique based on mask regional convolutional neural network (Mask-RCNN). By effectively utilizing the comprehensive information including genotyping, tumor mask, and prognosis, multitask technique, on the one hand, realized multi-purpose modeling and simultaneously, on the other hand, promoted the accuracy of the molecular subgrouping. One hundred and thirteen medulloblastoma cases were collected from 4 hospitals during the 8-year period in the retrospective study, which were divided into 3-fold cross-validation cohorts (N = 74) from 2 hospitals and independent testing cohort (N = 39) from the other 2 hospitals. Comparative experiments of different auxiliary tasks were designed to illustrate the effect of multitasking in molecular subgrouping.

Results

Compared to the single-task framework, the multitask framework that combined 3 tasks increased the average accuracy of molecular subgrouping from 0.84 to 0.93 in cross-validation and from 0.79 to 0.85 in independent testing. The average area under the receiver operating characteristic curves (AUCs) of molecular subgrouping were 0.97 in cross-validation and 0.92 in independent testing. The average AUCs of prognostication also reached to 0.88 in cross-validation and 0.79 in independent testing. The tumor segmentation results achieved the Dice coefficient of 0.90 in both cohorts.

Conclusions

The multitask Mask-RCNN is an effective method for the molecular subgrouping and prognostication of medulloblastomas with high accuracy in few-shot learning.

Update on Pediatric Brain Tumors: the Molecular Era and Neuro-immunologic Beginnings

PURPOSE OF REVIEW

To provide an update on the current landscape of pediatric brain tumors and the impact of novel molecular insights on classification, diagnostics, and therapeutics.

RECENT FINDINGS

Scientific understanding of the genetic basis of central nervous system tumors has expanded rapidly over the last several years. The shift in classification of tumors to a molecularly based schema, accompanied by a growing number of early phase clinical trials of therapies aimed at inhibiting tumoral genetic and epigenetic programs, as well as those attempting to harness and magnify the immune response, has allowed a deeper pathophysiologic understanding of brain tumors and simultaneously provided opportunities for novel treatment. Over the last 5 years, there has been tremendous growth in the field of pediatric neuro-oncology with increasing understanding of the genetic and epigenetic heterogeneity of CNS tumors. Attempts are underway to translate these insights into tumor-specific treatments.