ESTRO 2025 - Abstract Book

S3137

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2025

Table 1. Mean aHD (with standard deviation) for syngo.via and Contour+

Table 2. Mean Dice (with standard deviation) for syngo.via and Contour+

Conclusion: Carbon rod fiducial markers were identified and registered with ETD fluorography with lower mean SI index than gold cylinder fiducials on planning CT. Significantly lower mean aHD and higher mean Dice for barbell-shaped carbon fiducials than carbon rods indicated less impact on auto-segmentation of rectum when using syngo.via, though this was not significant for Contour+. Observed properties of carbon rods proved utility in prostate registration and tracking with ETD with potential preference over gold cylinder fiducial markers.

Keywords: fiducial markers, prostate cancer radiotherapy

2422

Digital Poster Initial feasibility assessment of a strict online imaging strategy for the prospective phase II HYPO-RT-PC boost trial (NCT06220435) Sacha af Wetterstedt 1,2 , Tobias Pommer 1 , Lars E Olsson 2 , Karin Söderkvist 3 , Tufve Nyholm 3 , Camilla Thellenberg Karlsson 3 , Joakim Jonsson 3 , Adalsteinn Gunnlaugsson 1 1 Department of Hematology, Oncology, and Radiation Physics, Skåne University Hospital, Lund, Sweden. 2 Medical Radiation Physics, Department of Translational Medicine, Lund University, Lund, Sweden. 3 Department of Diagnostics and Intervention, Radiation Physics, Umeå, Sweden Purpose/Objective: In the HYPO-RT-PC-boost trial, high-risk prostate cancer patients receive radiotherapy to the prostate (42.7 Gy, 5 mm margin), pelvic lymph nodes (29.4 Gy, 7 mm margin), proximal 2 cm of the seminal vesicles (31.2 Gy, 8 mm margin), and a focal boost to the intraprostatic lesion (49.0 Gy, 2 mm margin). The purpose of this work was to assess the feasibility of a strict online matching and treatment supervision strategy for the first patients included in the trial.