ESTRO 2025 - Abstract Book

S739

Clinical - CNS

ESTRO 2025

Results: Thirty-two were included in this study (Table 1).

Patients with HGG WHO grade3 received a total dose of 59.4Gy (33fractions of 1.8Gy) and 12cycles of adjuvant TMZ. Glioblastoma patients were treated with conventionally-fractioned RT (60Gy in 30fractions), concurrently with TMZ 75mg/m²/day, followed by 6cycles of TMZ. In all cases RT was delivered with Volumetric Modulated Arc Therapy (VMAT). After a median followup of 13.4months [2.4-26.6], 8 patients were alive, 7 (87.5%) without disease progression. Median PFS and OS were 10.3 and 17.1 months. At univariate analysis, low OS was associated with: WHO grade4(p.002), age>50years(p.008), IDH-wildtype(p.004), MRI residual disease(p.034), TBRmax>4.02(p.0001), MTVtot>40.25cc(p.0002), MTVmax>12.96cc(p.0001), and V GTV57Gy <99%(p<.0001). These parameters were associated with shorter PFS, as well as the MGMT-unmethylation(p.03), and V PTV57 Gy <96.4%(p.04). The multivariate analysis confirmed, as prognostic factor correlated with OS, the WHO grade4(p.013), the TBRmax>4.02(p.004), and the V GTV57Gy <99%(p.005). The factors correlated with PFS at multivariate analysis were WHO grading(p.001) and TBRmax(p.008). Conclusion: Our analysis confirms the prognostic role of biological parameters, highlighting the relevance of the maximal GTV coverage obtained by morphologic-metabolic integration.

Keywords: FET-PET, High Grade Glioma, Radiotherapy

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