IMG-93. Prognostic significance of PET RANO 1.0-based response assessment in patients with newly diagnosed <i>IDH</i> -wildtype glioblastoma

Abstract BACKGROUND The PET RANO 1.0 criteria, which were introduced in 2024, standardize response classification for diffuse gliomas based on amino acid PET imaging. However, the association between PET RANO responses and outcome is still unclear. In this study, we evaluated the correlation between early PET RANO responses and clinical outcome of patients with newly diagnosed glioblastoma. METHODS Patients with newly diagnosed IDH-wildtype glioblastoma who had received a baseline [18F]FET-PET scan prior to first-line radiotherapy (with or without chemotherapy) and a follow-up PET three months after the initiation of radiotherapy were included. Response classes (progressive disease (PET-PD), stable disease (PET-SD), partial response (PET-PR), and complete response (PET-CR)) were assessed using PET RANO 1.0 criteria, and correlated with progression-free survival (PFS), time to next intervention (TTNI) and overall survival (OS). Kaplan-Meier and log-rank tests were used for statistical analyses. RESULTS 126 patients with newly diagnosed glioblastoma were retrospectively analyzed with a median follow-up time of 19 months (95%CI [14.7, 23.3]). After radiotherapy, 49/126 patients (39%) had PET-PD, 21/126 (17%) PET-SD, 53/126 (42%) PET-PR, and 3/126 (2%) PET-CR, compared to the baseline PET. Patients with PET-PD demonstrated a significantly shorter TTNI compared to CR/PR/SD combined (median 5.0 vs. 10.0 months; p=0.005) and a shorter PFS (median 5.0 vs. 10.0 months; p=0.012). No significant OS differences were observed between PET RANO response classes (p=0.503). OS analyses are currently limited by a percentage of 59% censored events. Further univariate analyses revealed MGMT promoter methylation (present in 57/126 patients) to be prognostically relevant for longer PFS (median 11.0 vs. 6.0 months, p&amp;lt;0.001). CONCLUSIONS Our findings demonstrate significant associations between early PET RANO 1.0 responses and both TTNI and PFS in patients with newly diagnosed glioblastoma. Further follow-up assessments of our patients will evaluate if early PET RANO 1.0 responses translate into OS differences.