S2731
RTT - Patient preparation, immobilisation, and verification protocols
ESTRO 2026
Material/Methods: A single-centre retrospective review of consecutive HPB patients (Jan 2020–Dec 2022) was approved. Patients received coaching for AC and voluntary EBH. 4DCT quantified the maximum superior–inferior (SI) liver-dome motion during free breathing with AC. EBH reproducibility was defined as diaphragm-apex agreement between 3D EBH and the 4DCT exhale phase within ±1 mm (SI). Non-parametric tests explored associations between motion and patient factors, including diagnosis, age, sex, cirrhosis, BMI, GTV size/location, and belt position. Results: Seventy-nine patients were consented for radiotherapy; 78 underwent 4DCT (one excluded due to habitus). AC was tolerated by 73/78 (93.7%), Table 1. Under AC, SI liver-dome motion ranged from 0.5–18.3 mm (mean 6.57; median 5.3); 42 patients (57.5%) had ≤ 6 mm motion, 16 (21.9%) had 6–10 mm, and 15 (20.5%) had >10 mm motion. Motion was higher without AC (6.57 vs 15.9 mm; p=0.003). Among AC patients, EBH was achieved by 47/73 (64.4%). Of these, 40/47 (85.1%) reproduced the 4DCT end-exhale phase. In 7/47 (14.9%) patients, EBH was achieved but not reproducible relative to the 4DCT exhale position, and these patients exhibited greater residual motion (11.6 vs 6.2 mm; p=0.005). Apart from tumour location (Table 1), no patient factors predicted residual motion or EBH feasibility and reproducibility (all p>0.05). EBH feasibility was lower in patients with cirrhosis (57.4% vs 84.2%), with a near-significant difference (p=0.051).
adoption phase of SGRT in departments, emphasising the importance of robust staff training. Conclusion: SGRT has been described as an “independent observer”, reducing the frequency of treatment related events2. This study is the first to characterise types of RTE prevented by SGRT within a national ELS. Integrating SGRT within the radiotherapy workflow may introduce new risks4 and the types of RTE that SGRT may be associated with are detailed. References: 1. Freislederer P, Batista V, Öllers M, et al. (2022). ESTRO-ACROP guideline on surface guided radiation therapy. Rad Oncol, Volume 173, 2022, Pages 188- 196.2. Al-Hallaq H, Batista V, Kügele M, et al. (2021). The role of surface-guided radiation therapy for improving patient safety. Rad Oncol, Volume 163, 2021, Pages 229-236.3. UKHSA (2025) Safer radiotherapy: national patient safety radiotherapy event taxonomy. UKHSA, London. Available at https://www.gov.uk/government/publications/safer- radiotherapy-national-patient-safety-radiotherapy- event-taxonomy (accessed 6.11.25)4. Al-Hallaq H, Cerviño L, Gutierrez A, et al. (2022). AAPM task group report 302: Surface-guided radiotherapy. Med Phys, 49(4), e82–e112. Keywords: SGRT, safety, risk Characterising motion variability and patient factors in hepatobiliary radiotherapy: toward personalised motion management Amanda Webster 1,2 , Turmi Patel 1 , David Marsh 1 , Kristina Quingua 1 , Catharine Clark 2,3 , Maria A Hawkins 2,4 1 Radiotherapy and Proton Beam Therapy, UCLH, London, United Kingdom. 2 Medical Physics and Biomedical Engineering, UCL, London, United Kingdom. 3 Radiotherapy Physics, UCLH, London, United Kingdom. 4 Oncology Department, UCLH, London, United Kingdom Purpose/Objective: Radiotherapy professionals cannot reliably predict which patients with hepatobiliary (HPB) malignancies benefit from motion management, namely, abdominal compression (AC) or exhale breath-hold (EBH) [1, 2]. To address this, the primary aims were to assess pre- treatment feasibility of AC and EBH, quantify residual liver-dome motion under AC, and evaluate EBH reproducibility. The secondary aim was to determine whether patient factors [3] predict motion magnitude and the feasibility of AC or EBH, to inform patient- specific motion-management selection. Proffered Paper 2948
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