In 2012, an international consensus paper reported that medulloblastoma comprises four molecular subgroups (WNT, SHH, Group 3, and Group 4), each associated with distinct genomic features and clinical behavior. Independently, multiple recent reports have defined further intra-subgroup heterogeneity in the form of biologically and clinically relevant subtypes. However, owing to differences in patient cohorts and analytical methods, estimates of subtype number and definition have been inconsistent, especially within Group 3 and Group 4. Herein, we aimed to reconcile the definition of Group 3/Group 4 MB subtypes through the analysis of a series of 1501 medulloblastomas with DNA-methylation profiling data, including 852 with matched transcriptome data. Using multiple complementary bioinformatic approaches, we compared the concordance of subtype calls between published cohorts and analytical methods, including assessments of class-definition confidence and reproducibility. While the lowest complexity solutions continued to support the original consensus subgroups of Group 3 and Group 4, our analysis most strongly supported a definition comprising eight robust Group 3/Group 4 subtypes (types I–VIII). Subtype II was consistently identified across all component studies, while all others were supported by multiple class-definition methods. Regardless of analytical technique, increasing cohort size did not further increase the number of identified Group 3/Group 4 subtypes. Summarizing the molecular and clinico-pathological features of these eight subtypes indicated enrichment of specific driver gene alterations and cytogenetic events amongst subtypes, and identified highly disparate survival outcomes, further supporting their biological and clinical relevance. Collectively, this study provides continued support for consensus Groups 3 and 4 while enabling robust derivation of, and categorical accounting for, the extensive intertumoral heterogeneity within Groups 3 and 4, revealed by recent high-resolution subclassification approaches. Furthermore, these findings provide a basis for application of emerging methods (e.g., proteomics/single-cell approaches) which may additionally inform medulloblastoma subclassification. Outputs from this study will help shape definition of the next generation of medulloblastoma clinical protocols and facilitate the application of enhanced molecularly guided risk stratification to improve outcomes and quality of life for patients and their families.

Relapsed medulloblastoma (rMB) accounts for a considerable, and disproportionate amount of childhood cancer deaths. Recent advances have gone someway to characterising disease biology at relapse including second malignancies that often cannot be distinguished from relapse on imaging alone. Furthermore, there are now multiple international early-phase trials exploring drug–target matches across a range of high-risk/relapsed paediatric tumours. Despite these advances, treatment at relapse in pre-irradiated patients is typically non-curative and focuses on providing life-prolonging and symptom-modifying care that is tailored to the needs and wishes of the individual and their family. Here, we describe the current understanding of prognostic factors at disease relapse such as principal molecular group, adverse molecular biology, and timing of relapse. We provide an overview of the clinical diagnostic process including signs and symptoms, staging investigations, and molecular pathology, followed by a summary of treatment modalities and considerations. Finally, we summarise future directions to progress understanding of treatment resistance and the biological mechanisms underpinning early therapy-refractory and relapsed disease. These initiatives include development of comprehensive and collaborative molecular profiling approaches at relapse, liquid biopsies such as cerebrospinal fluid (CSF) as a biomarker of minimal residual disease (MRD), modelling strategies, and the use of primary tumour material for real-time drug screening approaches.

Relapse is the leading cause of death in patients with medulloblastoma, the most common malignant pediatric brain tumor. A better understanding of the mechanisms underlying recurrence could lead to more effective therapies for targeting tumor relapses. Here, we observed that SOX9, a transcription factor and stem cell/glial fate marker, is limited to rare, quiescent cells in high-risk medulloblastoma with MYC amplification. In paired primary-recurrent patient samples, SOX9-positive cells accumulated in medulloblastoma relapses. SOX9 expression anti-correlated with MYC expression in murine and human medulloblastoma cells. However, SOX9-positive cells were plastic and could give rise to a MYC high state. To follow relapse at the single-cell level, an inducible dual Tet model of medulloblastoma was developed, in which MYC expression was redirected in vivo from treatment-sensitive bulk cells to dormant SOX9-positive cells using doxycycline treatment. SOX9 was essential for relapse initiation and depended on suppression of MYC activity to promote therapy resistance, epithelial–mesenchymal transition, and immune escape. p53 and DNA repair pathways were downregulated in recurrent tumors, whereas MGMT was upregulated. Recurrent tumor cells were found to be sensitive to treatment with an MGMT inhibitor and doxorubicin. These findings suggest that recurrence-specific targeting coupled with DNA repair inhibition comprises a potential therapeutic strategy in patients affected by medulloblastoma relapse. Significance: SOX9 facilitates therapy escape and recurrence in medulloblastoma via temporal inhibition of MYC/MYCN genes, revealing a strategy to specifically target SOX9-positive cells to prevent tumor relapse.

Objectives: The growing population of survivors of childhood brain tumors present the challenge of long-term quality of survival. The domains most affected by tumor and treatment are those implicated in development of typical intellectual functions: attention, working memory, and processing speed, with consequent effects upon function and quality of life. In this paper we present service evaluation data on the 12-month effect upon processing speed, visual and auditory attentional domains in 29 patients receiving methylphenidate aged 5-16 years (Mean=10.6). Methods: Patients received immediate-release methylphenidate and were converted to modified-release as appropriate. Mean optimal dose of immediate-release methylphenidate was 0.34 mg/kg per dose (range 0.2-0.67). Results: Patients showed a significant positive impact of methylphenidate on attention in all tests of selective visual attention from the Test of Everyday Attention for Children 2. A significant improvement was also shown on response time. Significant change was not found on psychometric measures of sustained auditory or visual attention, or selective auditory attention. Ratings of Health-Related Quality of Life showed a positive benefit of methylphenidate at 12 months. Side effects were minimal and not statistically significant. Conclusions: Survivors of childhood brain tumor with attentional and processing speed deficit show clinical benefit from methylphenidate.

Background: The deleterious impact upon the cognitive development of survivors of pediatric brain tumors (PBT) is well documented. Impairment in cognitive function is associated with reduced health-related quality of life (HRQoL), such that survivors of PBT report difficulties in multiple distinct domains and an overall reduced quality of life. Studies of the use of methylphenidate in survivors of PBT to alleviate impairment in cognitive functions have shown some success. The current study aimed to explore the impact upon HRQoL in survivors of PBT of a trial of psychostimulant medication. Method: Data were collected from 12 pediatric neuro-oncology patients aged 7–17 years receiving methylphenidate treatment. HRQoL was measured using the PEDS QL quality of life self-report measure and a semi-structured questionnaire-based interview. Results: Analyses of data demonstrates benefit to five domains associated with HRQoL: social, emotional, academic, physical, and cognition. Conclusion: Survivors of PBT reported favorable views as to the subjective benefit of methylphenidate on post-treatment impairment of HRQoL. This medication may offer the potential for restoration of a sense of ‘normality’ of function following cancer treatment in this clinical population.

Background: Survivors of childhood brain tumour face significant neurocognitive late effects, including impairment in processing speed and attention. Deficits to these core cognitive domains contribute to the plateauing of age-appropriate intellectual development as the child matures. While short-term studies demonstrate the utility of methylphenidate in enhancing processing speed and attention during early recovery, its longer-term role in sustaining intellectual development remains underexplored. Methods: The current study examined the long-term effects of methylphenidate on intellectual development in 23 survivors of childhood brain tumour, matched on multiple clinical and demographic variables against 23 controls. Intellectual assessments were conducted at baseline and after 12 months of treatment. Statistical analyses evaluated the degree of change in intellectual trajectories between groups over time. Results: Bayesian hierarchical modelling showed distinct intellectual trajectories between groups, with consistent declines in the control group. Treatment with methylphenidate was associated with the preservation of age-appropriate intellectual development, with the highest posterior probability of treatment-related benefit to Fluid Reasoning (0.97), and strong-to-moderate evidence of benefits to Verbal Comprehension (0.92), Working Memory (0.91), and Processing Speed (0.84). Frequentist analyses supported these findings, demonstrating significant preservation of Fluid Reasoning over time (t = 2.14, p = 0.04). The use of chemotherapy was associated with a significant decline in Fluid Reasoning across the entire dataset; this effect was only sustained in the control group (β = − 18.6, p = 0.03). Conclusion: These findings highlight the long-term rehabilitative potential of methylphenidate and suggest its wider adoption could support care for survivors at risk of intellectual plateau.