ESTRO 2024 - Abstract Book

S4371

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

ESTRO 2024

CTV volumes of more than 10 cc obtaining less than 95% of the prescribed dose were present in 1% of the simulations for both IMRT and VMAT with typical DIBH performance (group A), but increased to 7% and 8% of the simulated fractions with worse DIBH reproducibility (group B), respectively.

For fraction dose delivery within 6 DIBHs, variation in mean CTV dose was less for the plans with a priori optimized 6 arcs (0.076 Gy) compared to clinical plans optimized with 3 arcs and delivered in 6 DIBHs (0.099 Gy).

Conclusion:

In our study, target breast dose in IMRT plans with a tangential 4-beam setup was more sensitive to DIBH variations than in VMAT plans with partial arcs, although much of the dose in IMRT plans is delivered from opposing directions. Our clinical VMAT plans show a relatively homogeneously distributed beam dose over the target volume, and this effect seems enhanced by using more beams in plan optimization. In short-course radiotherapy, dose inhomogeneity may not average out over the course of treatment for patients with a large variation in inspiration level during a fraction. Therefore, monitoring DIBH using surface guidance or spirometer-based systems with pre-set tolerance margins may be employed to minimize DIBH variation during treatment delivery.

Keywords: robust planning, breast, breath-hold

References:

1 Penninkhof et al, Tech Innov Patient Support Radiat Oncol. 2022 21:51-57. doi:10.1016/j.tipsro.2022.02.001