ESTRO 2025 - Abstract Book

S1479

Clinical – Mixed sites & palliation

ESTRO 2025

References: 1. Kroeze, S. G. C. et al. Toxicity of concurrent stereotactic radiotherapy and targeted therapy or immunotherapy: A systematic review. Cancer Treat. Rev. 53 , 25 – 37 (2017). 2. Kroeze, S. G. C. et al. Metastases-directed stereotactic body radiotherapy in combination with targeted therapy or immunotherapy: systematic review and consensus recommendations by the EORTC-ESTRO OligoCare consortium. Lancet Oncol. 24 , e121 – e132 (2023).

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Digital Poster CBCT-only workflow for bone metastasis, a feasibility study Jens Engleson 1 , Fernanda Villegas Navarro 2,3 , Anna Sundeman 1 , Laura Gallo 1 , Mattias Hedman 1,3 1 Department of Radiation Oncology, Karolinska University Hospital, Stockholm, Sweden. 2 Department of Medical Radiation Physics and Nuclear Medicine, Karolinska University Hospital, Stockholm, Sweden. 3 Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden Purpose/Objective: Palliative radiotherapy (RT) is common for painful bone metastasis and has effect in about 60% of treated patients (1). Treatment preparations require multiple visits to the clinic, including the acquisition of a dose-planning computed tomography (pCT). A new generation on-board image verification system enabling acquisition of cone beam CT (CBCT) imaging with Hounsfield unit (HU) values calibrated for dose planning were installed on two linear accelerators. This work explores the feasibility of a CBCT-only RT workflow where replacing the pCT by a CBCT image will shorten treatment preparation and first-fraction delivery time to one single visit beneficiating to the patient´s quality of life (2). Material/Methods: Mass density to HU measurements were performed to confirm the suitability of CBCT for dose planning. A retrospective study comparing dose distributions between pCT and CBCT images on 4 pelvic and 3 thorax patients was conducted using mock targets delineated and planed on the pCT as per clinical routine. Plans were then recalculated on the CBCT. The first step of workflow implementation was the identification of the tasks differing from routine pCT workflow, followed by a risk analysis to determine new method development and staff training. The initial workflow was tested using artificial patients, adjusting task guidelines after each session. Knowledge gaps needing further staff training were identified through interdisciplinary evaluations. Finally, an end-to end test was conducted to validate the new workflow.