Abstract BACKGROUND Diffuse midline glioma (DMG) is an invariably fatal diagnosis with a median survival of 9-11 months. While early death is uncommon, such cases do exist. Identification of children at risk of short-term survival can support clinicians to provide informed counselling to families regarding important treatment decisions. METHODS We identified patients with a radiological diagnosis of DMG at the Royal Children’s Hospital (Melbourne) and the Women’s and Children’s Hospital (Adelaide) between 2001-2023. Clinical, imaging, and histopathological data were abstracted and compared between short-term survivors (STSs) and longer survivors (LSs). RESULTS Among 89 patients included, 21 (24%) had an overall survival (OS) of < 6 months of which 7 (8%) had an OS < 3 months. 5 of these cases had dramatic early death with < 1 month since diagnosis. While neither the pattern nor presence of contrast enhancement were predictive of poor survival, STSs were found to have a larger volume of contrast enhancement on T1-weighted imaging compared to LSs (1.3 cm3 vs 0.2 cm3, p < 0.01). Evaluation of the presence and extent of intratumoural susceptibility signals (ITSS) on susceptibility weighted imaging (SWI) demonstrated higher grades of ITSS (> 5 foci) were strongly associated with poor survival (p = 0.01, median OS = 5.5 months). Furthermore, 50% (6/12) of STSs had ≥ 11 dot-like or fine linear ITSSs in a maximum tumour cross section. From a treatment standpoint, as expected, patients who did not receive upfront radiotherapy experienced significantly worse OS (3.4 months vs 10.4 months, p < 0.01). Notably, a number of STSs did not receive palliative therapy in the context of their rapid and unforeseen disease progression. CONCLUSIONS The preliminary findings from this multi-centre study provide the foundation for future exploratory analysis alongside international collaborators at the DMG/DIPG registry to improve prognostication for patients with high-risk features of early death.