ESTRO 2025 - Abstract Book

S4353

RTT - Treatment planning, OAR and target definitions

ESTRO 2025

Results: A governance framework for MIM software has been implemented within GenesisCare Australia. This has facilitated a systematic approach that seeks to optimise communication, safety and efficiency across multiple sites. Conclusion: Ongoing refinement and adaption of the governance framework will aim to maintain these goals in relation to changing technology, systems and organisational governing priorities.

Keywords: MIM, Workflow, Automation

2280

Proffered Paper Weighting Preferences for RapidArc Dynamic: An Evaluation of the Impact on One Arc and Two Arc Approaches for Treating Nasopharyngeal Carcinoma Catherine Laferlita 1 , Kenton Thompson 1,2 , Nicholas Hardcastle 1,2 , Vanessa Panettieri 1,2 , Thomas Devereux 1,2 , Tsien Fua 1,2 , Tomas Kron 1,2 , Pauline Lim 1 , Katrina Woodford 1,2 , Sandro Porceddu 1,2 1 Department of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, Australia. 2 Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Australia Purpose/Objective: RapidArc Dynamic (RAD) (Varian Medical Systems, Palo Alto, USA) is the most recent evolution in arc therapy, utilising dynamic collimation and combining the benefits of IMRT and VMAT in a single continuous delivery. RAD offers five different weighting preferences for treatment plan optimisation – Arc Dominant (AD), Arc (A), Balanced (B), Static (S) and Static Dominant (SD). Changing the weighting preference alters the allocation of control points (CP) and monitor units for the STatic Angle Modulated Ports (STAMPs). 1 This study aims to evaluate the impact of changing the weighting preferences on two RAD planning approaches for a cohort of patients who received curative intent radiation therapy with or without chemotherapy for locally advanced nasopharyngeal carcinoma (NPC). Material/Methods: Twenty T3-4, any N, M0 NPC patients who received curative intent radiation therapy with or without chemotherapy at our institution between 1 July 2019 and 1 July 2023 formed the cohort for the analysis. Two RAD approaches were developed using the default B weighting and optimised to achieve a clinically acceptable plan: 1. Single arc with five STAMPs – RAD1 2. Two arcs with four STAMPs per arc – RAD2 Each plan was copied and optimised with each alternate weighting preference, AD, A, S and SD. All other parameters were the same, resulting in each patient having a collection of ten plans (5 RAD1 and 5 RAD2 plans). Figure 1 demonstrates the number of control points for each preference. Target, Organs as Risk (OAR) and intermediate dose metrics were compared. Statistical differences were determined by a Wilcoxon signed-rank test (p ≤ 0.05).