ESTRO 2024 - Abstract Book

S774

Clinical - CNS

ESTRO 2024

Law I, Albert NL, Arbizu J, et al. Joint EANM/EANO/RANO practice guidelines/SNMMI procedure standards for imaging of gliomas using PET with radiolabelled amino acids and [18F]FDG: version 1.0. Eur J Nucl Med Mol Imaging. 2019;46(3):540-557. doi:10.1007/s00259-018-4207-9 Celli M, Caroli P, Amadori E, et al. Diagnostic and Prognostic Potential of 18F-FET PET in the Differential Diagnosis of Glioma Recurrence and Treatment-Induced Changes After Chemoradiation Therapy. Front Oncol. 2021;11(October):1-10. doi:10.3389/fonc.2021.721821

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Digital Poster

Pattern of recurrence after fractionated stereotactic body reirradiation in glioblastoma recurrence

Agathe Margulies 1 , Nassim Sahki 2 , Guillaume Vogin 3 , Marie Blonski 4 , Didier Peiffert 1 , Luc Taillandier 4 , Fabien Rech 5 , Grégory Lesanne 6 , Nicolas Demogeot 1 1 Institut de Cancérologie de Lorraine, Radiothérapie, Vandoeuvre-lès-Nancy, France. 2 Institut de Cancérologie de Lorraine, Biostatistiques, Vandoeuvre-lès-Nancy, France. 3 Centre François Baclesse, Radiothérapie, Esch-sur-Alzette, Luxembourg. 4 CHRU de Nancy, Neurologie, Nancy, France. 5 CHRU de Nancy, Neurochirurgie, Nancy, France. 6 Institut de Cancérologie de Lorraine, Radiologie, Vandoeuvre-lès-Nancy, France

Purpose/Objective:

Glioblastomas all eventually relapse after initial treatment, and an option to treat these recurrences is fractionated stereotactic body reirradiation (fSRT). The location of recurrences after reirradiation have been studied, but not precisely after fSRT delivered by a dedicated stereotactic device. We aimed to analyze the patterns of these recurrences after fSRT, as there is limited data to sharpen the choice of safety margins and dose and fractionation regimen.

Material/Methods:

We retrospectively analyzed the data of patients with glioblastoma recurrence reirradiated by fSRT between October 2010 and December 2020, in 25 Gy in 5 fractions delivered by a CyberKnife® at Institut de Cancérologie de Lorraine. We matched the images of the relapse post-fSRT with the stereotactic radiation treatment planning scan to determine the relapse location.

Results:

Among 62 patients, we found that the localization of recurrences after fSRT was “out - field” in 54.8%, “marginal” in 40.3% and “in - field” in 4.8%. The median PFS from fSRT was 3.4 months (95% CI 2.9 – 4.8 months). We found that age at initial treatment ≥ 65 years (HR 0.56 [95% CI 0.32 – 0.98], p = 0.041), KPS score at recurrence ≥ 70% (HR 0.27 [95% CI 0.08 – 0.89], p = 0.032), and existence of one or more previous recurrences (HR 2.44 [95% CI 1.16 – 5.13], p = 0.019), were significantly associated with PFS in univariate analysis. In multivariate analysis, we found that a KPS score ≥ 70% at recurrence (HR = 0.27 [95% CI 0.08 – 0.93], p = 0.038), PTV volume ≥ 35cc (HR = 3.61 [95% CI 1.23 –