S2695
RTT - Patient preparation, immobilisation, and verification protocols
ESTRO 2026
References: Mariados N, et al. Int J Radiat Oncol Biol Phys 2015;92:971-977. Wong CHM, et al. Prostate Cancer Prostatic Dis 2025. Miller LE, et al. JAMA Netw Open 2020;3:e208221. Keywords: Hyaluronic Acid, Hydrogel , Balloon Digital Poster 193 ExactTrac Dynamic Improves Accuracy and Speed of Setup for Breast Cancer Patients BILAL KRAYIM 1 , Aaron allen 2 , Raphael Pfeffer 3 , mohammad abu miyaleh 4 , hila rosenfield 5 , sion koren 4 , nir honig 4 , adar yaacov 4 1 helmsely cancer center, shaare zedek medical center, JERUSALEM, Israel. 2 helmsely cancer center, shaare zedek medical center, jeruslam, Israel. 3 shaare zedek medical center, shaare zedek medical center, jerusalem, Israel. 4 helmsely cancer center, shaare zedek medical center, jerusalem, Israel. 5 helmsely cancer center, shaare zedek medical center, jeruslaem, Israel Purpose/Objective: Background:Accurate and reproducible patient positioning is essential in breast cancer radiotherapy to ensure target coverage while minimizing exposure to surrounding healthy tissues. Conventional tattoo- based alignment remains widely used but has inherent limitations, including variability, potential setup errors, and the negative psychological impact of permanent markings. Surface Guided Radiation Therapy (SGRT) using ExacTrac Dynamic offers a non- invasive, real-time alternative that may improve reproducibility, workflow efficiency, and patient experience. Material/Methods: Methods:We conducted a retrospective analysis of patients treated for breast cancer at Shaare Zedek Medical Center between December 2022 and December 2024. Forty-nine patients (245 fractions) were positioned using SGRT with ExacTrac Dynamic, while a control cohort of 20 patients (100 fractions) underwent conventional tattoo-based alignment with daily kV imaging. Six-dimensional setup deviations (vertical, longitudinal, lateral, pitch, roll, rotation) and preparation-for-treatment (PFT) times were recorded. Statistical analysis was performed using non- parametric Mann–Whitney U tests, with effect sizes calculated by Cohen’s d. Results: Results:Median translational deviations for SGRT were –0.48 cm (vertical), –0.61 cm (longitudinal), and +0.06 cm (lateral), compared with +0.03 cm, –0.38 cm, and – 0.03 cm in the control group. Rotational deviations
analysis calculated pooled relative risks (RR) with 95% confidence intervals (CI). Statistical heterogeneity was evaluated using I ² statistics. Results:
Seventeen studies (3 RCTs, 14 observational studies) involving 3,200+ patients were included. Meta-analysis demonstrated significant reduction in late grade ≥ 2 rectal toxicity with spacer use (pooled RR=0.25, 95% CI: 0.15-0.42, P<0.001) with minimal heterogeneity (I ² =0%). Acute grade ≥ 2 gastrointestinal toxicity was also significantly reduced (pooled RR=0.53, 95% CI: 0.33-0.86, P<0.001). Dosimetric analysis showed mean rectal V70 reduction of >70% across all spacer types (hydrogel, hyaluronic acid, biodegradable balloon). Quality of life assessments revealed smaller declines in bowel-related function scores in spacer groups. Spacer implantation success rate exceeded 99% with minimal serious complications (<1%). Conclusion: Rectal spacers significantly reduce radiation dose to the rectum, decrease acute and late rectal toxicity by approximately 50-75%, and improve quality of life outcomes. These devices should be considered standard care for patients undergoing definitive prostate radiotherapy, particularly with hypofractionated regimens.
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