ESTRO 2024 - Abstract Book

S5569

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

ESTRO 2024

Purpose/Objective:

Exact treatment position during stereotactic body radiotherapy is crucial. We investigate the use of abdominal compression with compact and lightweight rail system (EAMIS Lite Macromedics) in reducing inter - and intrafractional motion.

Material/Methods:

Our study included 71 patients with 83 liver tumors treated stereotactic body radiotherapy in the period between 2021 and 2023 in a single centre. Tumor motion was assessed to every lesion. Patients laid supine on vacuum bag, arms up with kneefix and abdominal compression equipment. Online-matched cone beam computer tomography (CBCT) was received daily, before treatment and during radiotherapy. Initial setup error and intrafraction motion were determined for all patients and all fraction. Intrafractional changes in liver tumor motion > 4 mm were defined as significant. The statistical analysis was performed using Statistica ver 13.3software.

Results:

Total 255 measurments of set up error and intrafracion tumor movements were recorded. The mean (± SD) set up error in CBCT before treatment was 4.3 ± 4.5 mm, 4.9 ± 4.1 mm, and 4.6 ± 3.9 mm, in the LR, AP, and SI directions, respectively. The mean (± SD) liver tumor motion in CBCT during radiotherapy was 1.6 ± 1.8 mm, 2.0 ± 1.9 mm, and 2.3 ± 2.4 mm, in the LR, AP, and SI directions, respectively. Significant intrafractional changes in liver tumor motion were observed in 8 (3%) LR measurments, 17 (7%) AP measurments and 19 (7%) SI measurments

Conclusion:

Based on our observations abdominal compression is an effective and accepted method for reducing tumor motion during radiotherapy. In all instances the patients who had abdominal compression were able to tolerate this treatment position. The optimal margin is still controversial. A symmetrical 5mm margin around the tumor should be enough for this kind of immbilization technique.

Keywords: abdominal compression, liver metastasis

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