ESTRO 2025 - Abstract Book

S2911

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

ESTRO 2025

Both VMAT 4DCT and VMAT DIBH plans meet all clinical goals, except for the bowel loop. However, the VMAT DIBH plan achieves a lower average dose to the heart and ventricles (approximately 1 Gy) compared to the VMAT 4DCT plan. While VMAT DIBH offers a slight dose advantage for the 'bowel loop' over IMPT 4DCT , all clinical goals are met in both plans. In the contouring worst-case scenarios, both IMPT 4DCT and VMAT DIBH plans met all clinical goals except for the bowel loop, the most critical OAR due to its proximity to the target, and the left lung (Table 2).

Conclusion: Compared to the 4D-CT, DIBH-CT technique reduces target volume and inter-operator variability, providing a dosimetric advantage for VMAT planning in gastric MALT patients. However, 4D-CT remains a viable alternative for IMPT treatments due to its shorter delivery time, which minimizes the introduction of additional uncertainties during treatment.

Keywords: Gastric MALT, Contouring Variability, Radiotherapy

References: [1] Choi et al. Radiation Oncology (2019), 14:59. doi: https://doi.org/10.1186/s13014-019-1263-7 [2] Hoque et al. Cancers (2023), 15(24), 5735. doi: https://doi.org/10.3390/cancers15245735 [3] Yahalom et al. Int J Radiat Oncol Biol Phys. 2015 May 1;92(1):11-31. PMID: 25863750. doi: 10.1016/j.ijrobp.2015.01.009.