ESTRO 2025 - Abstract Book

S727

Clinical - CNS

ESTRO 2025

Material/Methods: We retrospectively reviewed the outcomes of patients with surgically resected BM who received adjuvant HSRT at our centre between 2015 and May 2024 Results: Ninety patients were identified with a median age of 57 (29-79). The most frequent primary tumours were lung (51%), breast (18%) and melanoma (14%). The targeted BM was single in 87%, with a median maximum diameter of 34,5 [28.0;41.00] mm. Complete resection was achieved in 85,2% of cases. Clinical conditions before RT were favourable in 87% of patients (Karnofsky index >70) and DS-GPA (diagnosis-specific graded prognostic assessment) was >3 in 53%. The median PTV was 24,1 [13,7;36,8] cm3. The most frequent RT schemes were 27 Gy in 3 fractions (35%) and 30 Gy in 5 or 6 fractions (34%). Treatment tolerance was excellent, except for one patient experiencing Grade 3 seizures (1,11%). The median interval between surgery and HFSRT was 55 [46,0;67,8] days. After a median follow-up of 25 months, local control of the surgical bed was achieved in 92,2% and 88,9% of cases at 1 and 2 years respectively. The presence of nodular residual tumour in surgical bed greater than 5 mm in size was associated to worst outcomes (HR 4,67). RN was observed in 15,7% of cases, with only 3,3% of grade 3. Treatment scheme was identified as a risk factor for RN (HR 1.89 for those schemes with BED alfa/beta 10 over 51 Gy). At 2 years cranial and extracranial progressions were seen in 47,2% and 48,3% of patients. Leptomeningeal spread was observed in 24,4% of patients. Whole brain radiotherapy was eventually administered to 14% of patients. Overall survival at 2 years was 56,2%. IKF <70 and DS-GPA<2 were identified as related with poorer survival (HR 3.11 and 2.62 respectively). Conclusion: HFSRT appears to be a highly effective option to increase local control probability after surgery in BM. Despite the uncertainties in volume contouring and the high number of large cavities, the use of fractionated schemes results in a low incidence of serious RN. Moderately hypofractionated schemes seems to be preferable for those cases with a higher risk of RN. Digital Poster Impact of resection extent and adjuvant radiotherapy in atypical meningioma WHO grade II Narudom Supakalin 1 , Wora-anong Thiramontri 1 , Sakda Wara-asawapati 2 , Siriwan Lulitanond 1 , Komsan Thamronganantasakul 1 , Chunsri Supaadirek 1 , Srichai Krusun 1 , Montien Pesee 1 , Yotdanai Namuangchan 1 1 Division of Radiation Oncology, Department of Radiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand. 2 Department of Pathology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand Purpose/Objective: Atypical meningioma is biologically more aggressive and has a poorer prognosis when compared to benign meningioma. Surgery is the mainstay of treatment with no standard guideline for adjuvant radiotherapy (RT). Aims of this study were to assess the impact of resection extent and adjuvant radiotherapy (RT) on progression-free survival (PFS) and recurrence risk in patients with atypical meningioma. Material/Methods: We retrospectively reviewed electronic medical records of eligible patients diagnosed with atypical meningioma WHO grade II who underwent surgery between 2008 – 2018 in Srinagarind Hospital, Faculty of Medicine, Khon Kaen University, Thailand. The primary outcome was PFS. The secondary outcomes were prognostic factors associated with PFS. Statistical analysis was performed with Kaplan-Meier method to determine PFS. Prognostic factors were analyzed using Cox proportional hazard model. A p -value of ≤ 0.05 was considered as statistically significant. Keywords: brain metastases, postoperative, radiotherapy 3611