ESTRO 2025 - Abstract Book

S686

Clinical - CNS

ESTRO 2025

1974

Digital Poster Outcomes of reirradiation for recurrent high-grade gliomas: a retrospective analysis of dose and timing effects on survival Sara Estrella-Márquez, Ana M Burgueño-Caballero, Inés Ollinger-Casín, Jose J Gordito-Soler, Pedro Romero-Pareja, Elena Montero-Perea Radiation Oncology, Virgen del Rocío University Hospital, Sevilla, Spain Purpose/Objective: First-line treatment for high-grade gliomas is well-established, but there is no standard approach for treatment after recurrence. Few patients are candidates for re-resection, and many have already undergone radiotherapy, raising concerns about the side effects of reirradiation. This retrospective study aims to evaluate overall survival (OS) following recurrence and assess treatment-related toxicities. Additionally, we investigate the relationship between the administered dose and survival, as well as the impact of relapse timing on post-reirradiation survival. Material/Methods: This study analyzed patients treated with reirradiation for recurrent high-grade gliomas at our center between 2014 and October 2024. A total of 26 patients were included, but survival analysis was conducted on 22 patients, as 4 were still undergoing treatment. Results: The median age of the cohort was 56 years (range 24–76). Most patients (86.36%) received the STUPP protocol as initial treatment. The median time from initial radiation therapy to reirradiation was 19.5 months. The most common reirradiation regimen was 25 Gy in 5 fractions, with a median planning target volume (PTV) of 27 cc (range 6.3–360 cc). The median follow-up after reirradiation was 7 months (range 1–41 months). The 6-month OS rate was 63.64%, and the 1-year OS rate was 31.82%. The median OS after reirradiation was 13 months. For glioblastoma patients, the median OS was 7 months, whereas for grade 3 gliomas, it was 12 months. In 80.76%, the IDH was identified as wild-type Patients were categorized into three dose groups: low (<30 Gy), medium (30–40 Gy), and high (>40 Gy). No significant differences were found between low and medium doses, or low and high doses. However, a significant difference in survival was observed between the medium and high-dose groups (p = 0.0288), suggesting improved survival with higher doses. Survival was also compared based on relapse timing: early relapse (<12 months) versus late relapse (>12 months). Late relapsers had significantly longer survival after reirradiation (p = 0.04016).