ESTRO 2025 - Abstract Book

S4052

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2025

without the pressure of manually pausing the beam in between arcs (only a 2 second pause). The use of thorax slow mode is under evaluation for its efficacy in showing tumour movement in a CBCT scan.

Conclusion: Lung SABR treatments can be completed on Halcyon and Ethos machines, with an interim scan taking place after a small isocenter shift on a multiple isocenter plan ensuring there is optimum radiation safety for these patients. Due to a lack of gating capabilities on the Halcyon machine, a CBCT taken in thorax slow mode and the use of abdomen compression and SGRT allows for tracking tumour and patient surface motion.

Keywords: SABR, Lung, SGRT, Ring gantry

References: Kiser, K., Schiff, J., Laugeman, E., Kim, T., Green, O., Hatscher, C., Kim, H., Badiyan, S., Spraker, M., Samson, P., Robinson, C., Price, A., & Henke, L. (2023). A feasibility trial of skin surface motion-gated stereotactic body radiotherapy for treatment of upper abdominal or lower thoracic targets using a novel O-ring gantry. Clinical and translational radiation oncology , 44 , 100692. https://doi.org/10.1016/j.ctro.2023.100692

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Poster Discussion PERSIAN trial (NCT05717660): reproducibility setup analysis within a randomized controlled trial Andrea Lastrucci 1,2 , Sara Tagliasacchi 1,2 , Elisa Moabiti 1,2 , Letizia Scaglione 1,2 , Elisa Consumi 1,2 , Neda Haghighatjou 1,2 , Martini Elisabetta 1,2 , Giulio Rossi 1,2 , Nicola Iosca 1,2 , Pietro Donatini 1,2 , Monica Morroni 1,2 , Giulio Francolini 2 , Vanessa Di Cataldo 2 , Pietro Garlatti 2 , Michele Aquilano 2 , Niccolò Bertini 2 , Yannick Wandael 1 , Renzo Ricci 1 , Lorenzo Livi 3 1 Department of Allied Health Professions, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy. 2 Radiation Oncology Unit, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy. 3 Department of Experimental and Clinical Biomedical Sciences “M. Serio”, University of Florence, Florence, Italy Purpose/Objective: The Persian study is a clinical trial evaluating the efficacy of stereotactic body radiation therapy (SBRT) in patients with metachronous oligometastatic hormone-sensitive prostate cancer. Participants receive either systemic therapy alone or in combination with SBRT. PERSIAN trial offers the unique opportunity to evaluate the reproducibility of patient positioning within a randomized trial exploring the benefit of SBRT. Aiming to evaluate site-specific immobilization devices and setup reproducibility, here we present a subgroup analysis performed on the first 31 patients treated with volumetric modulated arc therapy technique. Material/Methods: Set-up shifts were analyzed for each treatment fraction, stratifying the sample into three categories based on metastatic site: Scapular target, thoracic region and abdominal/pelvic region. The corresponding immobilization devices included a thermoplastic mask, a vacuum cushion with overhead arm support and a vacuum cushion in combination with the feetfix system, respectively. Shifts were assessed by CBCT matching and quantified using 3D vector displacement to assess isocenter shifts.