The European Cooperative Study Group for Paediatric Rare Tumours (EXPeRT group): a model for collaborative research and clinical care in very rare paediatric tumours

Paediatric cancers, though all considered rare, have benefited substantially from international collaborative protocols. However, very rare tumours (VRTs) in children and adolescents, defined by an annual incidence of <2/1 000 000, pose significant challenges. These malignancies represent >50 different histotypes and collectively account for ∼11% of all paediatric cancers. The European Cooperative Study Group for Paediatric Rare Tumours (EXPeRT) was established in 2008 to address the unique challenges posed by these rare malignancies through collaborative research, multidisciplinary clinical expertise, and international cooperation. Over the past 15 years, EXPeRT has established a comprehensive framework integrating expert clinical consultation, harmonised consensus guideline development, retro- and prospective collaborative research, and strategic international partnerships. This article provides a comprehensive overview of EXPeRT’s structure, scientific contributions, and vision for future cross-disciplinary and cross-border initiatives aimed at improving outcomes for children and adolescents with VRTs. • EXPeRT provides expert multidisciplinary consultation for very rare paediatric tumours across Europe. • Harmonised European guidelines for diagnosis and treatment of paediatric VRTs have been developed by EXPeRT. • The PARTNER registry enables prospective data collection for paediatric VRTs across European centres. • A virtual tumour board facilitates equitable access to VRT expertise, impacting management in >90% of cases. • PARTNER4VRT establishes a transatlantic platform to standardise data and foster future interventional studies.