ESTRO 2024 - Abstract Book

S748

Clinical - CNS

ESTRO 2024

Hacettepe University, Radiation Oncology, Ankara, Turkey

Purpose/Objective:

Although first-line management has been nearly standardized over the years for patients with glioblastoma, the optimal management of progressive disease after initial treatment is still controversial. Re-operation, systemic therapies and re-irradiation are common treatment approaches. In this study, we aimed to evaluate the prognostic factors and the role of stereotactic radiotherapy (SRT) as a re-irradiation technique in the management of progressive glioblastoma.

Material/Methods:

Records of 77 previously irradiated patients who received reirradiation in our department were evaluated retrospectively. Statistical Package for the Social Sciences (SPSS) version 25.0 (IBM, Armonk, NY, USA) was utilized for all statistical analyses.

Results:

Patient, tumor, and treatment characteristics are presented in Table 1. A total of 77 patients with progressive glioblastoma were included in the analysis. The median age was 48 (range, 19 – 77 years) and the median GTV volume was 36 cc (range, 8 – 98.5 cc). The median time to progression from the end of initial RT was 14 months (range, 6 – 68 months). The most common SRT schedule was 30 Gy (range, 18 – 50 Gy) in 5 fractions (range, 1 – 5 fractions). Median follow-up after SRT was 9 months (range, 3-80 months). One-year overall (OS) and progression free survival (PFS) rates after SRT were 46% and 35%, respectively. One-year OS (60% vs. 32%, p = 0.001) and PFS (47% vs. 22%, p = 0.007) rates were significantly higher in patients who progressed >14 months after initial RT. Patients receiving a ≥40 Gy equivalent dose in 2 Gy per fraction (EQD2) of SRT had better 1 -year OS (56% vs. 20%, p = 0.001) and PFS (47% vs. 15%, p = 0.001). Patients experiencing pseudoprogression after SRT had better 1-year OS (75% vs. 37%, p = 0.052) and PFS (59% vs. 28%, p = 0.005). In multivariate analysis, progression-free interval > 14 months, EQD2 of SRT ≥40 Gy, and presence of pseudoprogression were significant independent positive prognostic factors for both OS and PFS. Treatment was well tolerated without significant acute toxicity. During follow-up, radiation necrosis was observed in 17 patients (22%), and 14 (82%) of them were asymptomatic.

Table 1. Patient, tumor and treatment characteristics

Characteristics

Number (n, %)

Gender

Male Female

45 (58) 32 (42)

Initial RT dose / fraction

60 Gy in 30 fractions 40 Gy in 15 fractions

71 (92) 6 (8)

Surgery at progression