ESTRO 2024 - Abstract Book

S4682

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

ESTR0 2024

coverage was preserved over the treatment for at least 90% (pass-rate) of the patients as described by van Herk et al. (1). Additionally the mean heart dose and the mean lung dose and V5 in the lungs were evaluated on the rCTs. Two years mortality was calculated, using a validated NTCP model for mean heart dose employed for patient selection in the Netherlands. (2,3)

Results:

The pass-rate was only achieved for the setup robustness setting of 8 mm for the end inhale and the end exhale phase with 90% and 100% respectively (Figure 1).

The dose in the OAR decreases significantly for every millimeter decrease in the setup robustness setting (p<0.05).

For online plan adaptation coverage is maintained during treatment for 80% of the patients. For 20% of the patients with lower coverage than prescribed the coverage was at least 97.7%, which is considered acceptable in clinical practice. Dose in the OAR decreases significantly compared to a non-adaptive treatment with a setup robustness error of 8 mm (p<0.01).

Conclusion:

Reducing the setup robustness settings for esophageal IMPT leads to a significant decrease in dose to the organs at risk and the predicted 2-years mortality. However, this cannot be achieved by merely reducing the setup robustness settings, as it leads to under dosing the target area. Offline adaptation of the treatment plan may mitigate this.