ESTRO 2025 - Abstract Book

S652

Clinical - CNS

ESTRO 2025

and neurosurgery were extracted from the REDCap database. Causality was assessed by the local and principal investigators, and the SAEs were categorised according to the treatment arm.

Results: 41 patients had been randomised in five centres in three countries at the time of analysis; 22 patients into Arm 1 (preoperative SRS) and 19 patients into Arm 2 (postoperative FSRT). Regarding toxicity, there were 19 SAEs in 15 patients from three centres. 11/19 SAEs were neurological; 9/11 were 'possibly' and 2/11 were 'probably' related to either radiotherapy or neurosurgery and all were grade 3 (Table 1).

Neurological SAE grade 3

Arm 1 (preop SRS) Arm 2 (postop FSRT)

Epileptic seizure

0

5

Hydrocephalus malresorptivus

0

1

Repeat craniotomy

1

2

Subdural haematoma

0

1

Symptomatic cerebral oedema

0

1

Total

1

10

Table 1 Reported SAEs possibly or probably related to radiotherapy or neurosurgery. The seven unrelated SAEs included keratitis, ileus, diarrhoea, leg ulcer, progression of an unresected brain metastasis after SRS, pneumonia and/or pneumonitis, resection of the primary lung tumour and an epileptic seizure after discontinuation of antiepileptic medication. All patients recovered from the grades 3 and 4 SAEs. The single grade 5 event was unrelated and followed immunotherapy-related diarrhoea. Regarding feasibility, preoperative SRS was performed in all 21 patients. The interval between preoperative SRS and resection of the brain metastasis was a mean of 1.9 (SD 1.94) days, within the maximum 1 week interval. The mean interval to start of postoperative FSRT was 21.9 (SD 11.6) days, within the recommended 30 days. The data were reviewed by the trial monitoring committee consisting of the investigators who, in view of the favourable toxicity and feasibility results for preoperative SRS compared with standard of care, decided to proceed with the trial. Conclusion: The planned interim analysis of the PREOP-2 randomised trial shows feasibility and low toxicity of preoperative SRS and the trial will continue to accrue.

Keywords: Radiosurgery, preoperative, brain metastases

References: [1] Prabhu RS, Dhakal R, Vaslow ZK, Dan T, Mishra MV, Murphy ES, et al. Preoperative Radiosurgery for Resected Brain Metastases: The PROPS-BM Multicenter Cohort Study. Int J Radiat Oncol Biol Phys. 2021. [2] Rogers S, Schwyzer L, Lomax N, Alonso S, Lazeroms T, Gomez S, et al. Preoperative radiosurgery for brain metastases (PREOP-1): A feasibility trial. Clin Transl Radiat Oncol. 2024;47:100798.

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Poster Discussion The dose-dependent effect of radiotherapy on functional brain network hubs and the resulting cognitive dysfunction in glioma patients Laurien De Roeck 1,2 , Rob Colaes 3 , Patrick Dupont 4 , Stefan Sunaert 3 , Steven De Vleeschouwer 5 , Paul Clement 1 , Charlotte Sleurs 6 , Maarten Lambrecht 7