ESTRO 2025 - Abstract Book

S3230

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2025

dose constraints with high-weighted objectives declined CTV quality with only an 8s time gain. A median optimization time of about 4min was obtained in this patient cohort. Patient-specific OAPT optimization times stayed consistent over fractions with minor variations correlated to tumour shrinkage/growth and related number of spots (Fig.1b). Compared to offline-adapted scenarios (manual adaptation for same rCTs as in clinic, dose recalculation otherwise), the OAPT plans showed consistently good results, e.g. target coverage was fulfilled on 100%/77% of rCTs for online/offline adaptation.

Conclusion: Template-based re-optimization facilitates automated online-adaptive planning with acceptable efficiency for NSCLC patients in a commercial TPS. Patient-specific online optimization times are predictable prior to treatment. Nevertheless, further acceleration is desired and could be accomplished through future GPU-based optimization or workflow adjustments combined with partial adaptation 2 .

Keywords: Online adaptation, Proton therapy, Lung cancer

References: 1 Troost EGC, Zschaeck S, Bütof R, et al. Randomisierte Studie zum Vergleich von Nebenwirkungen nach Protonen- versus Photonen-Strahlentherapie bei Patienten mit fortgeschrittenem nichtkleinzelligen Bronchialkarzinom. Forum . 2022;37(2):153-155. doi:10.1007/s12312-022-01059-7 2 Gambetta V, Fredriksson A, Menkel S, Richter C, Stützer K. The partial adaptation strategy for online ‐ adaptive proton therapy: A proof of concept study in head and neck cancer patients. Med Phys . 2024;51(8):5572-5581. doi:10.1002/mp.17178