QLTI-09. Redefining rarity: a global mapping of clinical trials and published evidence on intracranial non-meningeal mesenchymal tumors

Abstract BACKGROUND Intracranial non-meningeal mesenchymal tumors are a rare and diverse group of CNS neoplasms, newly delineated in the 2021 WHO Classification of CNS Tumors (WHO CNS5). To evaluate the impact of this reclassification, we conducted a global mapping of clinical trials and literature to identify gaps in evidence, inclusion, and geographic equity. METHODS We performed a two-pronged global mapping strategy: (1) a review of all registered clinical trials from ClinicalTrials.gov and the EU Clinical Trials Register, and (2) a structured literature review via PubMed and Google Scholar over the past 10 years, using both current and pre-2021 WHO CNS5 classification terms. Extracted variables included publication year, study type, geographic origin, patient number, age group, tumor subtype, and treatment details. Study conclusions were qualitatively synthesized to identify management patterns across subtypes. RESULTS We identified 49 clinical trials, including 40 interventional and 9 observational studies (4 patient registries). Among interventional trials, 32 were early-phase, 30 had a treatment focus, and 6 were randomized. Only three trials were conducted outside high-income regions, and only one involved a site in a low- and middle-income country (LMIC). Of 416 published studies, 44% originated from LMICs and 27% focused on pediatric populations. Most (90%) were case reports, including 11% with literature reviews; 7% were retrospective cohorts, and 0.7% were prospective trials. Most frequently reported subtypes were solitary fibrous tumor/hemangiopericytoma (30%), Ewing sarcoma (14%), and DICER1-mutant sarcoma (9%). Qualitative analysis revealed distinct patterns: solitary fibrous tumors were often misdiagnosed as meningiomas but showed aggressive behavior; DICER1-mutant sarcomas were genetically complex and often misdiagnosed without molecular profiling. CONCLUSION This global mapping highlights major gaps in the study of intracranial non-meningeal mesenchymal tumors, particularly in pediatric and LMIC settings. The analysis of available data serves as the linchpin for developing recommendations for the management of this distinct group of neoplasms.