ESTRO 2025 - Abstract Book

S2818

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2025

Conclusion: The automated planning solution for prostate treatments has been accepted for clinical use for prostate treatments due to effective target coverage, improved organ-at-risk protection and better plan deliverability results compared to manual plans.

Keywords: autoplanning, deep learning, prostate cancer

2472

Digital Poster Advantages and limitations of navigation-based multicriteria optimization in sparing pharyngeal constrictor muscles in head and neck radiotherapy Laura Howard 1 , Simon Meara 2 , Carl Rowbottom 1 1 Physics, Clatterbridge Cancer Centre NHS Foundation Trust, Liverpool, United Kingdom. 2 Physics, The Christie NHS Foundation Trust, Manchester, United Kingdom Purpose/Objective: Sparing pharyngeal constrictor muscles (PCM) during radiotherapy planning improves patient-reported swallowing function [1]. This study aimed to explore the feasibility of integrating knowledge-based planning (KBP) with multicriteria optimization (MCO) in Eclipse™ v18.0 to selectively spare PCM, to quantify the required trade-off (TO) in low-risk planning target volume (PTV54) coverage, and to evaluate MCO performance. Material/Methods: Ten patients previously planned with RapidPlan® KBP for oropharyngeal cancer (65Gy, 60Gy and 54Gy in 30 fractions) were retrospectively re-planned. Clinical plans were further optimized using TO exploration in MCO, with a priority order: critical organ-at risk (OAR) sparing, high-risk (PTV65) and intermediate-risk (PTV60) target coverage, PCM, PTV54 coverage, parotids, remaining OAR. Plans were evaluated based on PTV dose metrics (D 50% , D 98% and D 2% ), homogeneity index (HI), conformity index (CI), and maximum and mean doses to OAR. Differences between navigated and deliverable plans were also analysed. One patient underwent ten identical repeat plan generations, and plan navigation for five patients was repeated using only the sliders. Results: MCO reduced the average mean dose to the superior and middle PCM, inferior PCM, contralateral parotid and larynx by 2.0Gy, 3.4Gy, 2.6Gy and 3.9Gy, respectively (p<0.05) but at the expense of HI and CI. No significant difference was observed in PTV54 D 98% between techniques, however all clinical plans and seven MCO plans achieved D 98% ≥ 95%, with three MCO plans modestly compromised (D 98% 93.7% - 94.6%). Dose metrics between navigated and deliverable