ESTRO 2025 - Abstract Book

S1470

Clinical – Mixed sites & palliation

ESTRO 2025

Purpose/Objective: Radiation treatment planning typically requires planning computed tomography (pCT) scanning, but it and subsequent treatment planning take several days, delaying radiotherapy. Simulation-free radiotherapy (SFRT) is an emerging technique that uses a patient’s diagnostic CT (dCT) instead of pCT for radiation treatment planning, and its utility has been shown in several studies [1 – 3] . SFRT may reduce both the time spent by patients in a Radiotherapy Department and the number of patient visits. This study investigated the feasibility of SFRT and possibility of completion within 1 day from the initial consultation. Material/Methods: We initiated a single-arm prospective interventional study (UMIN-CTR: UMIN000054721) in June 2024, with the following eligibility criteria: i) the patient consented to palliative radiotherapy for vertebral bone metastasis, ii) dCT could be performed without the patient wearing a corset or other external device within the previous 56 days at our institution, iii) irradiation could be performed in the supine position, and iv) the bone metastasis needing treatment could be identified on dCT. The primary and secondary endpoints were the radiotherapy completion rate and the time in center (TIC) (time from entering the consultation room to radiation beam off), respectively. The patients were treated with anteroposterior – posteroanterior parallel-opposed pairs or a direct posteroanterior field with 8 Gy in 1 fraction. Figure 1 shows the trial schema. Cone beam CT (CBCT) was mandatory for patient setup. SFRT was to be discontinued if CBCT revealed a treatment target deformity or major body contour changes that were considered difficult to correct by image-guided radiotherapy.