10118- NI-8 RADIOLOGICAL AND MOLECULAR ANALYSIS OF EARLY-STAGE GLIOBLASTOMA REVEAL THE RADIOLOGICAL INITIATION OF IDH WILDTYPE GLIOBLASTOMA

Abstract Glioblastoma (GB), IDH wildtype, is an aggressive and malignant tumor that necessitate early surgical intervention upon radiological suspicion. Consequently, the natural growth dynamics of GB remain not fully understood. Previous studies have examined GB growth using multiple MRIs between initial radiological diagnosis of GB and preoperative MRI, but these studies have short-term intervals between MRIs (defined as shortGB-cohort). Therefore, the shortGB-cohort requires extrapolations to determine radiological initiation which harbors greater uncertainty. In this study, we focused on early-stage GB (eGB), characterized by small, nonspecific lesions on MRI that eventually progress to classic GB findings. We compared three cohorts: 49 cases of eGB. 68 cases of shortGB, and 23 cases of eGB from previous publications (other-eGB). Molecular analyses revealed that TERT promoter mutations, EGFR amplification/gain, CDKN2A hemi/homozygous deletion, and PTEN hemi/homozygous deletion were consistent between eGB and shortGB. Our analysis indicated that the radiological initiation of GB in eGB was -0.84 years (95% confidence interval (CI): -1.09 to -0.68), compared to -0.35 years (95%CI: -0.46 to -0.28) in shortGB. In eGB, factors such as age<65, MIB1>30%, TERTp mutation, and the presence of copy-number alterations (CNA) in EGFR/PTEN/CDKN2A, with or without TERTp mutation, correlated with faster tumor progression. In cases without these alterations, the estimated radiological initiation was -2.31 years (95%CI: -100 to -0.80), indicating slower progression. The ShortGB-cohort did not show any significant changes based on these factors, suggesting it does not actually reflect tumor origin. The other-eGB cohort presented radiological initiation between -0.92 and -0.15 year, consistent with our eGB-cohort. This study investigates the radiological origin of GB using extremely rare cases of eGB. This cohort minimizes the extrapolations, providing insights into the radiological pathophysiology and its association with molecular alterations in IDH-wildtype GB.