S2254
Physics - Intra-fraction motion management and real-time adaptive radiotherapy
ESTRO 2026
Digital Poster 3689
Indexed pneumatic abdominal compression for respiratory motion reduction in lung stereotactic ablative radiotherapy Yohan A Walter 1,2 , Daniel B Speir 3 , Chiachien J Wang 1 , Megan M Rodrigues 3 , James C Henry 3 , Carlos D Palomeque 1 , William E Burrell 3 , Philip F Durham 3 , Olivia G Moncrief 4,3 , Emily G Warren 4,3 , Hsinshun T Wu 1 1 Radiation Oncology, Nuclear Oncology, Willis Knighton Cancer Center, Shreveport, USA. 2 Clinical Research, University of Jamestown, Fargo, USA. 3 Radiation Oncology, Willis Knighton Cancer Center, Shreveport, USA. 4 School of Medicine, Louisiana State University Health Shreveport, Shreveport, USA Purpose/Objective: Respiratory motion management remains a significant challenge in radiation therapy for lung tumors. Stereotactic ablative radiotherapy (SABR) utilizes high dose levels delivered in contracted treatment regimens, placing heavy demands on motion mitigation and mechanical accuracy. Indexed pneumatic abdominal compression may enhance motion management by restricting breathing patterns, while distributing force over a larger area compared to compression paddles. In this study, we investigate the impact of pneumatic abdominal compression on respiration-induced tumor motion. Material/Methods: Patients were prospectively enrolled in this motion management study. Patients were simulated in the headfirst supine position, with arms up and a knee wedge for comfort. The Body Pro-Lok ONE indexed pneumatic abdominal compression belt (BPL1, CQ Medical) was placed over the upper abdomen and inflated. A respiration-correlated CT scan (4DCT) was acquired. The belt was then removed, and a repeat 4DCT was acquired without abdominal compression. A third 4DCT was then acquired with the patient repositioned and compression reapplied for assessment of reproducibility. Gross tumor volumes (GTV) were contoured on the maximum intensity projection (iGTV_MIP) generated for each 4DCT. An isotropic 5.0 mm margin was applied to the iGTV_MIP to compare simulated treatment volumes. Paired t- tests were used to compare target volumes and iGTV_MIP dimensions between tested conditions. Statistical significance was taken as p<0.05. Results: 10 patients with 12 total lesions (8 upper lobe, 3 lower lobe, 1 right middle lobe) were analyzed. Abdominal compression unanimously lowered the iGTV volume in all cases, reducing by 0.9 ± 0.3 mL on average (p<0.01). The average iGTV was 2.8 ± 2.0 mL (range 0.5-7.2 mL) with BPL1, and 3.7 ± 2.6 mL (range 0.7 to 7.6 mL) without BPL1. The resulting iPTV reduced by 2.4 ± 0.7
Conclusion: Intra-fractional position correction significantly reduced baseline shifts during SBRT for central lung lesions in the STRICT-Lung trial, improving geometric accuracy and treatment stability. Despite steep dose gradients and close proximity to OARs, the dosimetric impact of residual motion after correction was negligible. The low incidence of grade 3+ toxicity supports the safety of this adaptive workflow and underscores the clinical value of intra-fractional imaging and correction in achieving precise, safe dose delivery for central lung SBRT. References: [1] L Hoffmann, et al. Thorough design and pre-trial quality assurance (QA) decrease dosimetric impact of delineation and dose planning variability in the STRICTLUNG and STARLUNG trials for stereotactic body radiotherapy (SBRT) of central and ultra-central lung tumours. Radiother Oncol, 171 (2022), pp. 53- 61.[2] Tekatli H, et. al. Outcomes of Hypofractionated High-Dose Radiotherapy in Poor-Risk Patients with "Ultracentral" Non-Small Cell Lung Cancer. J Thorac Oncol. 2016 Jul;11(7):1081-9.[3] Lindberg K, et al. The HILUS-Trial-a Prospective Nordic Multicenter Phase 2 Study of Ultracentral Lung Tumors Treated With Stereotactic Body Radiotherapy. J Thorac Oncol. 2021 Jul;16(7):1200-1210. Keywords: Intra-fraction motion management, Lung SBRT
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