S1448
Interdisciplinary - Other
ESTRO 2026
considered prescription or peak dose relevant for local control. For GRID, dose was prescribed to Dmax (60%, n=3/5) or to the gross tumour volume with a margin (100%, n=3/3), the latter being considered to influence local control. 58% (n=21/36) prescribed a valley dose as low as reasonably achievable. SFRT education was largely inadequate, with 88% (n=131/149) lacking formal training. Although 37% (n=56/150) had not yet implemented SFRT, 15% (n=22/150) planned to start soon. Most respondents showed interest in multicentre clinical trials (81%, n=120/149), considering lack of guidelines (71%, n=53/75) and institutional support (54%, n=65/149) as main implementation barriers. Conclusion: SFRT is gaining clinical adoption, mainly for bulky tumours, though its use remains heterogeneous, particularly in planning and clinical purposes. Guidelines, structured education, and collaborative clinical trials to standardise and advance SFRT practice are urgently needed. References: 1. Mayr NA, Mohiuddin M, Snider JW, et al. Practice Patterns of Spatially Fractionated Radiation Therapy: A Clinical Practice Survey. Advances in Radiation Oncology. 2024;9(2):101308. doi:10.1016/j.adro.2023.1013082. Zhang H, Mayr NA, eds. Spatially Fractionated, Microbeam and FLASH Radiation Therapy: A Physics and Multi-Disciplinary Approach. IOP Publishing; 2023. doi:10.1088/978-0- 7503-4046-5.Figure 1: Worldwide distribution of the frequency of clinical SFRT use among 150 respondents (n=149 countries). Keywords: spatially fractionated radiotherapy, survey Appropriateness of Palliative Radiotherapy in Patients With ≤30-Day Survival: A Comprehensive Cancer Center Retrospective Analysis João M Silva 1 , Laura S Serrão 1 , Pedro Moreira 1 , Miguel Catalo 1 , Isabel Rocha Miguel 1 , João Basílio 1 , Olga Sousa 1 , José A Ferraz-Gonçalves 2 , Luísa Samarão 1 , Eduardo M Rocha 1 1 Radiation Oncology, IPO-Porto, Porto, Portugal. 2 Departamento de Medicina da Comunidade, Informação e Decisão em Saúde, FMUP, Porto, Portugal Purpose/Objective: Radiotherapy (RT) plays a key role in symptom palliation for advanced cancer patients; however, when administered too close to death, its clinical benefit becomes questionable (1). The proportion of patients receiving RT in the last weeks of life has been proposed as an indicator of treatment aggressiveness Digital Poster 3135
Purpose/Objective: Despite increasing spatially fractionated radiotherapy (SFRT) clinical practice, its clinical/scientific evaluation and implementation remains ill-defined1. We aimed to characterise current SFRT practices and expectations in Europe and beyond. Material/Methods: A four-section online questionnaire addressing SFRT clinical use, technique, planning, quality control, education, and regulatory aspects was distributed from June–October 2025 to radiation oncology professionals via EORTC, ESTRO, and social media. Descriptive statistics, frequency distributions, and permutation tests were used for group comparisons. Results:
130/154 survey visitors completed the questionnaire, representing 39 countries across four continents, mainly in Europe (Fig.1).Most respondents were radiation/clinical oncologists (82%, n=123/150), and 60% (n=90/149) used SFRT clinically. Regarding the total number of patients treated, 8% (n=4/50) are planning, 22% (n=11/50) treated <5, 56% (n=28/50) 6- 100, and 14% (n=7/50) >100 patients, yielding an estimated total of >900. Predominant indications were bulky tumours (68%, n=32/47) and intra-abdominal metastases (40%, n=19/47). Bulky disease was defined as >5 cm (75%, n=36/48) or symptom burden (46%, n=22/48). SFRT was mainly used palliatively (87%, n=39/45), curatively (32%, n=13/41), or in reirradiation (63%, n=24/38). Dose and fractionation schemes varied widely. SFRT was often combined with external beam radiotherapy (palliative: 32%, n=13/41; curative: 73%, n=8/11) and/or systemic therapy (56%, n=22/39), predominantly chemotherapy or immunotherapy (86%, n=19/39 each). Most common techniques were Lattice (LTR) (32%, n=48/150), multileaf collimator- based GRID therapy2 (13%, n=19/150), stereotactic body radiotherapy – partial tumor irradiation targeting hypoxic segment (12%, n=18/150), stereotactic central/core ablative radiotherapy (11.3%, n=17/150), collimator-based GRID (7.3%, n=11/150), minibeam, microbeam and particle GRID therapy (each 3.3%, n=5/150). In LTR, 83.3% (n=20/24) prescribed the dose to the vertex tumour volume, while 43% (n=9/21)
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