ESTRO 2025 - Abstract Book

S3356

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2025

Conclusion: The preliminary results demonstrated the feasibility of accurate and robust eye tracking during the radiotherapy with the device. However, further tests should be carried out to assess the degree of eye fixation under different conditions.

Keywords: Uveal melanoma, eye videotracking, SRT

References: 1. Semeniuk, O.; Yu, E.; Rivard, M.J. Current and Emerging Radiotherapy Options for Uveal Melanoma. Cancers 2024, 16, 1074. https://doi.org/10.3390/ cancers16051074

4548

Digital Poster Assessing the need for adaptive cardiac radioablation for left ventricular tachycardia Sarah Cradick 1 , Geoffrey Hugo 1 , Clifford G. Robinson 1 , Pamela Samson 1 , Phillip Cuculich 2 , Kaitlin Moore 1 , Eric D. Morris 1 1 Radiattion Oncology, Washinton University, St. Louis, USA. 2 Cardiology, Washinton University, St. Louis, USA Purpose/Objective: Cardiac radioablation (CRA) is an emerging treatment for refractory ventricular tachycardia (VT) [1]. Due to the single fraction delivery, positional changes in nearby organs at risk (OARs) can force abandonment of the delivery. Combining CRA with online adaptive capabilities has the potential to lower dose to surrounding OARs (e.g. stomach, esophagus, and untargeted heart). This study seeks to outline the potential benefits of integrating online adaptive capabilities into CRA to better manage the on-treatment position of OARs. Material/Methods: Imaging datasets were gathered for fifty-one patients treated off-label. Datasets included the original simulation CT and a secondary imaging dataset. Segmentations of the heart, esophagus, stomach, and PTV were acquired for both datasets. A rigid registration was completed based on the whole heart and the dose was transferred to the secondary image. Centroids, volumes, and dose metrics were gathered for OARs and the PTV. Left ventricle (LV) segments encompassing the target were tabulated and correlated against variations in dose (Table 1). Results: Stomach volume variations up to 235.6% (-12.6% ± 60.2%) and positional variations in 3D up to 4.7cm (2.2cm ± 1.1cm) were observed. 8 of 51 patients had a difference in maximum dose to the stomach >10Gy. One representative patient had a maximum point dose to the stomach increase from 10.7Gy to 23.0Gy which exceeds the clinical tolerance of 22.0Gy [2]. Key dose metrics for the stomach were significantly different (p<0.05) between datasets, with an average change of 4.03Gy. Dose metrics were not significantly different for the esophagus with an average change of 2.8Gy. Dosimetric variations >10Gy were not significantly linked to the LV segments closest in proximity to the stomach. Conclusion: This study revealed two scenarios of stomach placement where adaptive capabilities would benefit CRA treatments (Figure 1). Adaptive CRA could improve OAR sparing by delivering a safer reoptimized plan that meets previously exceeded dose constraints. Additionally, it could allow for the generation of a more aggressive plan on the day of treatment for patients with suboptimal stomach placement at the time of treatment simulation. This study did not reveal the position in the esophagus to be variable enough to justify online adaptation. Due to the nature of VT, electrical abnormalities can be present in any of the 17 segments of the LV. No correlation was identified between large dose variations and the targeted LV segments. Thus, patient-specific determinations must be made when justifying adaptation for CRA.