Rare paediatric central nervous system (CNS) tumours form a biologically heterogeneous set of low-incidence diseases that pose substantial challenges for therapeutic development and clinical research. Definitions vary, but ‘very rare’ childhood cancers have been suggested as those with an incidence below 2 per million per year. More commonly studied CNS entities (for example low- and high-grade glioma, medulloblastoma, ependymoma) occur at rates of roughly 1.5–5 per million per year and are typically investigated through large, coordinated, randomized international trials. By contrast, tumour types such as choroid plexus carcinoma (CPC) and atypical teratoid rhabdoid tumour (ATRT) are far rarer (incidences below 1.5 per 10 million per year cited), and novel molecularly defined entities such as embryonal tumour with multilayered rosettes (ETMR) and very high-risk medulloblastoma (VHR-MB) strata have extremely low incidences (for example ETMR reported as ~3 per 100 million per year and VHR-MB ~1 per 10 million per year in referenced material).
Because individual rare CNS tumour types yield small patient numbers, assembling investigational cohorts and conducting randomized trials has been difficult. Treatments are often extrapolated from other tumour types, cohort and registry studies, or case reports. Collectively, though individually uncommon, these tumours comprise a substantial portion of paediatric neuro-oncology diagnoses and are associated with poor cure rates for some entities and significant late-effect burdens among survivors.
The UK paediatric neuro-oncology community convened a multi-disciplinary workshop to explore how clinical trials for these rare tumour types can be more effectively delivered and how every patient can contribute to shared knowledge and improved care.
The workshop took place in London in January 2026 and was jointly facilitated by the UK Collaborative for Cancer Clinical Research (UK3CR) Children’s Cancer Research Group (CRG) CNS Tumours Subgroup, and Cancer Research UK Clinical Trials Units at the University of Birmingham (CRCTU) and University College London (Cancer Trials Centre, CTC). Contributors included twenty-four experts covering trials unit leadership, statisticians expert in advanced trial designs, and clinicians and allied specialists across oncology, radiotherapy, radiology, endocrinology, late-effects and translational science. The meeting also included early-career researchers (ECRs) and patient and public involvement and engagement (PPIE) partners.
Discussions combined presentations, tumour-specific deep-dives, and sessions on cross-cutting trial methodology. The programme also incorporated strategic overviews of UK–European–North American trial delivery challenges and prioritised follow-up commitments to develop trial concepts, registries, and advisory structures. A subsequent UK3CR Children’s CRG CNS Tumour Subgroup meeting in March 2026 reviewed workshop outputs and refined next steps.
The workshop structured its workstream around four rare CNS tumour groups considered to require immediate coordinated action:
Tumour selection aimed to exemplify different unmet needs and operational challenges: the need for morbidity-focused trials (craniopharyngioma), rarity despite established pathology (CPC), rare high-risk molecular subgroups within a more common tumour (VHR-MB), and newly defined molecular entities (REST/ETMR).
The workshop produced several tumour-specific conclusions and priorities:
Craniopharyngioma: The group considered the feasibility of a UK-led craniopharyngioma trial, with emphasis on addressing morbidity and late effects. Specific trial design or operational details were not reported in the source beyond feasibility being a key outcome.
CPC: Participants identified a need for enhanced national CPC data collection to support investigational cohort assembly and inform trial design. The source does not provide the exact data infrastructure proposed.
VHR-MB: The group supported European early-phase platform trials for VHR-MB molecular strata (Group3-MYC and SHH-MYCN), reflecting the potential value of transnational collaborative early-phase evaluation for rare high-risk subgroups.
REST (including ETMR): REST discussions emphasised transnational regulatory complexity, noting that coordinated registries and parallel trial models would be required to overcome regulatory and operational barriers. Exact regulatory solutions were not specified in the source.
Workshop participants identified multiple cross-cutting barriers that limit the feasibility and timeliness of clinical trials in rare childhood CNS tumours. These included:
These barriers were framed as structural impediments that need harmonised, internationally-aligned solutions to enable efficient trial delivery.
To maximise efficiency in very small patient populations, the workshop emphasised innovative trial methodologies. Key methodological approaches recommended included:
The workshop underscored that these designs, coupled with strengthened patient involvement and international collaboration, could improve the evidence base for both existing and novel treatments in rare CNS tumours.
Consensus strategic themes from the meeting coalesced around several priorities for coordinated action:
The report positions these recommendations as the basis for an internationally-aligned strategic roadmap to accelerate clinical research and improve outcomes in rare paediatric CNS tumours.
A UK3CR Children’s CRG CNS Tumour Subgroup meeting in March 2026 reviewed the workshop outputs and refined next steps; the source confirms this follow-up but does not provide detailed minutes or operational plans within the manuscript excerpt. Additionally, the provided source text ends partway through a section describing the UK3CR perspective, so further detail from later sections of the original article (for example specific trial concepts, timelines, funding strategies, or governance models) was not reported in the excerpt supplied.
Overall, the workshop concluded that combining registries, contemporary trial designs, international platform approaches, and coordinated regulatory/funding strategies offers a feasible path to improve the delivery of clinical trials in rare childhood CNS tumours and to strengthen the evidence base guiding care.