ESTRO 2025 - Abstract Book

S3523

Physics - Optimisation, algorithms and applications for ion beam treatment planning

ESTRO 2025

Results: For both modalities, 9/14 66Gy-plans and 10/14 50Gy-plans met the full target coverage constraints while complying with CURE Lung constraints. The target compromises for the remaining patients were comparable between the modalities and primarily due to the connective tissue constraint . Three 66Gy-plans had V95%<80% while two had V95%>95%. Two 50Gy-plans had V95%<80% while three had V95%>95%. The proton plans had 1.3Gy and 1.7Gy lower mean lung doses for 66Gy-plans and 50Gy-plans, respectively. Likewise, mean heart doses were 1.3Gy and 1.2Gy lower, see Figure1. These differences were all significant (p<0.001). In the overlap between the chest wall and the 90Gy(EQD2)-isodose of the primary plan, D0.1cc for the photon reirradiation plans were maximally 19Gy and maximally 14Gy for protons.

Conclusion: Reirradiation plans could be created with both modalities without a target compromise for most patients, but no target coverage benefit was observed for proton compared to photon planning. Proton plans achieved better