ESTRO 2025 - Abstract Book

S3242

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

ESTRO 2025

Results: CTV D 50% = 54 Gy (RBE) was achieved with high probability for all plans, however with a larger spread in the dose to the target for proton therapy as shown for one patient in Figure 2. Nevertheless, proton therapy reduced the dose to most included organs at risk compared with photon therapy. For the proton plans the ipsilateral lung absolute volumes at dose V 5 Gy were always smaller while V 11.4 Gy and V 20 Gy was smaller for 13 and 10 of the 14 patients respectively, compared with the photon plans.

Conclusion: Proton SBRT and photon SBRT plans were compared. The results indicate that proton SBRT can be delivered with guaranteed target coverage and reduced dose to organs-at-risk, even for patients with large respiratory motion. Further investigations of implications in dose delivery dynamics and interplay will be addressed in future studies.

Keywords: SBRT, Proton therapy, Probabilistic evaluation

References: [1] Wikström, K.A., Isacsson, U.M., Pinto, M.C., Nilsson, K.M., Ahnesjö, A., 2021. Evaluation of irregular breathing effects on internal target volume definition for lung cancer radiotherapy. Med. Phys. 48, 2136–2144. https://doi.org/10.1002/mp.14824

2046

Digital Poster Assessing uterine intra-fractional motion and implementation of reduced PTV margins for cervical online adaptive radiotherapy David G Moore, Rachel Hollingdale, Matthew A Bolt, Alexandra J Stewart, Adrian Franklin, Dualta McQuaid, Elizabeth J Adams Radiotherapy, Royal Surrey Foundation Trust, Guildford, United Kingdom