ESTRO 2025 - Abstract Book

S4055

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

ESTRO 2025

Periprocedural discomfort is common, but HA, RBI and HG spacers generally are well tolerated. Evidence, especially for HG spacers, consistently demonstrates that IRS effectively reduce rectal radiation dose, thereby minimizing acute and long-term GI toxicity. However, its use should be guided by careful consideration of individual patient needs to determine those who benefit most from IRS, as not all patients may benefit equally.

Keywords: Implantable rectal spacers, prostate cancer

References: 1. Sung H, et al. Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality for 36 Cancers in 185 Countries. CA Cancer J Clin. 2021;71(3):209-49. doi:10.3322/caac.21660. 2. Kissel M, et al. Dose-escalation in prostate cancer: Results of randomized trials. Cancer Radiother. 2022;26(6 7):899-904. doi:10.1016/j.canrad.2022.07.011. 3. Zaorsky NG, et al. Ideal radiotherapy dose for prostate cancer? A meta-analysis of dose escalation. Radiother Oncol. 2015;115(3):295-300. doi:10.1016/j.radonc.2015.05.011. 4. Vanneste BG, et al. Chronic radiation proctitis: prevention and treatment. Int J Colorectal Dis. 2015;30(10):1293 303. doi:10.1007/s00384-015-2289-4.

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Digital Poster Improving the selection of fiducial-less lung patients for CyberKnife radiosurgery: Recommendations for patient selection, simulation and workflow Milad Mirzaei 1,2 , Nicholas Bucknell 1 , Joshua Dass 1 , Angela Jacques 3,4 , Clare Herbert 1 , Martin Ebert 1 , Sean Bydder 1 1 Department of Radiation Oncology, Sir Charles Gairdner Hospital, Nedlands, WA, Australia. 2 School of Physics, Mathematics, and Computing, The University of Western Australia, Crawley, WA, Australia. 3 Department of Research, Sir Charles Gairdner Hospital, Nedlands, WA, Australia. 4 Institute for Health Research, The University of Notre Dame, Fremantle, WA, Australia Purpose/Objective: Lung cancer is the leading cause of cancer deaths worldwide. 1 Stereotactic ablative radiotherapy (SABR) has shown to improve survival in patients with early-stage lung cancer. 2 CyberKnife ® is a robotic radiosurgery system which delivers SABR treatment via a comprehensive non-coplanar workspace. Target localisation and tracking during treatment is achieved by Synchrony ® Xsight ® Lung Tracking System (XLTS). XLTS allows soft tissue-based tumour tracking without invasive fiducial implantation in a proportion of patients that either do not want surgical intervention due to a risk of pneumothorax or are not clinically fit for fiducial implantation. 3 The aim of this study was to optimise CyberKnife ® simulation techniques and improve patient selection for SABR treatment. A secondary aim was to provide a comprehensive patient selection guideline to improve resource allocation and reduce time delays. Material/Methods: A total of 30 fiducial-less lung cancer patients that underwent CyberKnife ® simulation were included in this study. Accuray Precision ® System was utilised to quantify patient tumours based on their region, size (mm), volume (cm 3 ), and Hounsfield unit (HU). Tumours were classified into apical (superior to the aortic arch), central (within the zone of the proximal bronchial tree), chest wall-abutted (<1.0 cm to the chest wall), diaphragmatic (<2.0 cm to the diaphragm), and peripheral. The impact of tumour size, volume and HU on simulation results ( i.e., success or failure in tumour detection) was evaluated using linear regression models.

Results: Tumour size, volume and HU determined simulation outcomes ( P <0.05). Apical, chest wall-abutted, and peripheral