S2769
RTT - RTT contouring, target definition, and treatment planning
ESTRO 2026
Conclusion: Our results demonstrate that dCT can substitute sCT for palliative RT planning without significant dosimetric compromise. Utilising existing dCT scans may streamline workflow, reduce treatment delays, and alleviate departmental resource burden while maintaining treatment quality. Further prospective studies may support wider clinical adoption of dCT- based planning in palliative settings. References: 1. Wong S, Roderick S, Kejda A (2021). Diagnostic Computed Tomography Enabled Planning for Palliative Radiation Therapy: Removing the Need for a Planning Computed Tomography Scan. Pract Radiat Oncol. 10.1016/j.prro.2020.10.0102. Ho QA, Smith- Raymond L, Locke A, Robbins JR (2021). Dosimetry Comparison of Palliative Radiation Plans Generated From Available Diagnostic CT Images Versus Dedicated CT Simulation for Inpatients. Cureus. 10.7759/cureus.177993. O'Neil M, Laba JM, Nguyen TK, Lock M (2024). Diagnostic CT-Enabled Planning (DART): Results of a Randomized Trial in Palliative Radiation Therapy. Int J Radiat Oncol Biol Phys. 10.1016/j.ijrobp.2024.03.005 Keywords: Palliative, Simulation-free, Dosimetry Preservation by precision: feasibility study of innovative static Proton Arc Therapy (PAT) in esophageal cancer patients Petra Klinker, Sabine Visser, Bas A. de Jong, Margriet Dieters, Jannet Beukema, Erik Korevaar, Johannes A. Langendijk, Stefan Both, Christina T. Muijs Radiation Oncology, University of Groningen, University Medical Centre Groningen, Groningen, Netherlands Mini-Oral 1134
within 4 weeks from sCT scan, with no major anatomical changes or radiological interventions. dCT scans were imported into the Eclipse Treatment Planning System. Image registration of dCT to sCT, allows transfer of planning target volume contours from sCT to dCT. The sCT plan was copied and reassigned with dCT scan and recalculated using the same dose prescription, beam parameters and monitor units. To minimize variations associated with CT number–to–electron density calibration differences between scanners, dCT plans were calculated with heterogeneity correction turned off. The primary endpoint looks at the mean dose (Dmean), maximum dose (Dmax), the minimum dose received by 95% of the PTV (D95) and the homogeneity Index (HI) of the plans. The analysis of the results used paired, two- tailed t-tests to compare dosimetric endpoints. Results: A total of 34 patients were analysed. sCT Dmean (102.1%, range: 94.9% – 113.4%) versus dCT Dmean (101.6%, range: 94.9% – 113.4%), with no statistically significant difference (p=0.578). Similarly, sCT Dmax (112.3%, range: 103.1% – 132.8%) was comparable to dCT Dmax (111.5%, range: 102.6% – 132.6%) (p=0.694). sCT D95 (95.6%, range: 87.9% – 100.5%) and dCT D95 (95.1%, range: 86.6 – 101.2%) were also similar (p=0.493). The mean homogeneity index (HI) was 1.12 (range: 1.03 – 1.33) for sCT and 1.11 (range: 1.02 – 1.32) for dCT (p=0.709).
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