ESTRO 2025 - Abstract Book

S725

Clinical - CNS

ESTRO 2025

Primary endpoint: progression-free survival (PFS). Secondary endpoints: overall survival (OS) and IORT-related neurotoxicity (CTCAEv4). Kaplan-Meier analysis evaluates PFS and OS, using IBM-SPSS software for statistical assessments. Results: 12 patients have been enrolled, with a median-age of 62 years (60–72), 91.7% were male. Surgery followed the standard of care, with BM primarily originating from lung carcinoma (66.7%) and melanoma (25%). Lesions were evenly distributed between right/left hemispheres. IORT was successfully administered in all cases, with the most commonly used applicator being 2.5cm (41.7%), followed by 3.0cm (33.3%). Complete resection was achieved in 58.3%, while 41.7% underwent subtotal-resection. The toxicity profile was favorable, 66.7% experienced no notable complications, while 16% had motor-related neurological-deficits, and 8.3% each reported postoperative-seizures and headaches. No cases of radionecrosis were observed. Local-recurrence occurred in one patient (8.3%) who had a subtotal resection, while 91.7% remained recurrence free. Half of the patients have died due to progression of the primary tumor, with a median follow-up time in the survival curve of 20.1 months. Conclusion: IORT following the resection of BM is associated with improved local control. A dose of 20Gy appears to be efficient and feasible for this purpose demonstrating a favorable toxicity profile, aligning with the limited literature published. Digital Poster Impact of dosimetric parameters analysis in fractionated radiotherapy for brain metastasis. Esther Agudo Rey 1 , Victoria Vera Barragán 1 , César Rodríguez Alarcón 2 , María Medina Cobacho 1 , Patricia Ruiz Leal 1 , María C Fernández Alcala 1 , Carmen Corral Fernández 1 , Yésika Rios Kavadoy 1 , Joaquín J Cabrera Rodríguez 1 , María F Ropero Carmona 1 , Juan B Quirós Rivero 1 1 Radiation Oncology, University Hospital of Badajoz, Badajoz, Spain. 2 Radiophysics, University Hospital of Badajoz, Badajoz, Spain Purpose/Objective: Brain metastasis are the most frequent CNS tumors in adulthood. Their management is considered one of the main challenges to achieve better overall survival (OS) and quality of life of patients. Single or multiple fraction radiosurgery has been established as the therapeutic standard in people with metastatic brain disease limited and good functional status. This study is performed to assess dosimetric parameters as predictors of radiation-induced brain toxicity after fractionated stereotactic radiosurgery (fSRS). Material/Methods: A retrospective review of 73 brain metastases in 55 patients treated at our center between July 2019 and December 2023 with a median age of 62 years (30-87) were performed. Histology most frequent was NSLC (63%). 52,8% of the patients had 2 metastases treated at the same time. Every treatment planning was reviewed to register the dosimetric parameters: PTV volume, Brain-GTV V30, V25, V12 and V20. When 2 or more lesions were treated, a sume of the volumes was analyse. Logistic regression was used to assess the relationship between GTV/PTV or brain volume and side effects, especially radionecrosis. Keywords: Intraoperative Radiotherapy, Brain Metastases 3459