Molecular Characterization and Treatment Approaches for Pediatric H3 K27-Altered Diffuse Midline Glioma: Integrated Systematic Review of Individual Clinical Trial Participant Data

Abstract

Diffuse midline glioma (DMG), H3 K27-altered are highly aggressive, incurable central nervous system (CNS) tumors. The current standard palliative treatment is radiotherapy, with most children succumbing to the disease in less than one year from the time of diagnosis. Over the past decade, there have been significant advancements in our understanding of these heterogeneous tumors at the molecular level. As a result, most of the newer clinical trials offered utilize more targeted approaches with information derived from the tumor biopsy. In this systematic review, we used individual participant data from seven recent clinical trials published over the past five years that met our inclusion and exclusion criteria to analyze factors that influence overall survival (OS). We found that the most prominent genetic alterations H3.3 (H3F3A) and TP53 were associated with worse OS and that ACVR had a protective effect. In addition, re-irradiation was the only statistically significant treatment modality that showed any survival benefit. Our findings highlight some important characteristics of DMG, H3 K27-altered and their effects on OS along with the importance of continuing to review clinical trial data to improve our therapies for these fatal tumors.

Diffuse Midline Gliomas: Challenges and New Strategies in a Changing Clinical Landscape

“…In 2021, this definition was expanded to include other alterations of histone 3 to “DMG H3K27-altered,” whereby other mutations that lead to chromatin remodeling alterations (e.g., loss of H3K27 trimethylation) can be included under the DMG umbrella [ 11 ]. In a majority of samples, the H3K27M alterations are due to mutations in two key histone genes: HIST1H3B/C (H3.1) and H3F3A (H3.3) [ 12 ].…”

“…Further studies are now trying to segment DMG location and associated mutations; albeit the literature is in need of larger longitudinal studies, new research has emerged indicating how certain anatomical locations have a stronger association with specific mutations (e.g., thalamus with TP53 or ATRX ; and pons with ACVR ). Similarly, mutations are now being associated with gender (e.g., ACVR with the female gender) and with outcome (e.g., TP53 yielding lower survival and ACVR longer) [ 12 ]. Noticeably, given the new WHO definition of pediatric DMGs, prior work where survival was associated with different genetic and histone alterations (e.g., [ 8 ]) has to be reanalyzed in light of these new molecular histopathological entities.…”