ESTRO 2025 - Abstract Book

S717

Clinical - CNS

ESTRO 2025

Keywords: brain metastases, financial toxicity

References: 1 Brown et al., Effect of Radiosurgery Alone vs Radiosurgery With Whole Brain Radiation Therapy on Cognitive Function in Patients With 1 to 3 Brain Metastases. JAMA. 2016 Jul 26;316(4):401-409. 2 Yamamoto et al., Stereotactic radiosurgery for patients with multiple brain metastases (JLGK0901): a multi institutional prospective observational study. Lancet Oncol. 2014 Apr;15(4):387-395. 3 Mulvenna et al., Dexamethasone and supportive care with or without whole brain radiotherapy in treating patients with non-small cell lung cancer with brain metastases unsuitable for resection or stereotactic radiotherapy (QUARTZ): results from a phase 3, non-inferiority, randomised trial. The Lancet. 2016 Oct;388(10055):2004-2014.

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Digital Poster Black Blood MRI: The secret weapon for contouring agreement

Gloria Sánchez Naranjo 1 , Gloria Guardia López 1 , Claudia Fernández Pedrero 1 , Zhao Chen Zhou 2 , Jennifer Paola Caguana Calle 1 , Fernando García Luque 1 , Pablo Alcaide Córdoba 1 , Mariana Temes Ramos 1 , Juan Pablo Kim Kim 1 , Elena Gómez Duque 1 , Alba Delgado Domínguez 1 , Alberto Fernández Romero 1 , Cristian Arias Guillén 1 , Francisco Javier Martínez Paredes 1 , Sandra Fernández Alonso 1 , Sandra Guardado González 1 , Laura Fernández Banda 1 , Sara Pedraza Fernández 1 , Irene Alda Bravo 1 , Nieves Gascón Costoso 1 , María Colmenero Hernández 1 , Pedro Adaimi Hernández 3 , Virginia Rodríguez González 1 , Maria Ángeles Pérez-Escutia 1 , Rafael D'Ambrosi 1 1 Department of Radiation Oncology, Hospital 12 de Octubre, Madrid, Spain. 2 Department of Radiology, 12 de Octubre Hospital, Madrid, Spain. 3 Department of Medical Physics, Hospital 12 de Octubre, Madrid, Spain Purpose/Objective: High-quality radiotherapy depends on precise contouring, particularly in patients receiving high-dose reatments with steep dose gradients. Despite advancements in radiotherapy delivery, interobserver variability in contouring remains a primary source of inconsistency. This study evaluated whether lack blood MRI (MSDE) improves contouring agreement compared to standard contrast-enhanced T1-weighted imaging (T1C) using the Dice similarity coefficient (DSC). Material/Methods: In this prospective study, 10 patients with 13 brain metastases were included. Lesions were contoured for the sole purpose of the study and were not used clinically. Contouring was performed independently by a specialist and three residents using standard 1C sequences and MSDE (black blood MRI). The delineated volumes were fused and interobserver agreement was assessed using the DSC averaged across observer pairs for each sequence. Differences in DSC were compared statistically using the Wilcoxon test. Results: The segmented volume obtained using MSDE was greater compared to that obtained with the T1C sequence, with median values of 2.17 cc (range: 0.10-9.85) for T1C and 2.36 cc (range: 0.13-10.26) for MSDE. Statistical analysis using the Wilcoxon test yielded a W value of 89, with p = 0.003, indicating a significant difference between the two methods. The DSC values indicated improved interobserver agreement with MSDE (0.90 ÷ 0.04) compared to T1C (0.88 ÷ 0.05). Agreement among residents improved from 0.87 (T1C) to 0.90 (MSDE), while agreement between the specialist and residents increased from 0.87 (T1C) to 0.89 (MSDE). The difference in DSC between sequences was statistically significant (W=74,p=0.023W = 74, p = 0.023W=74,p=0.023). Notably, the choice of imaging sequence had a greater impact on agreement than the level of observer experience.