ESTRO 2024 - Abstract Book

S3678

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

ESTRO 2024

uncertainties, by assigning each voxel the highest possible EQD2 value within a sphere with radius equal to the OAR-specific MDA, and compared the original summed dose to this robust summation.

Results:

Five out of six patients had clinically acceptable plans using the novel EQD2-based planning approach; compared with three for the standard planning pathway. Blinded, qualitative evaluation showed a strong preference for the EQD2-based plans for three of the patients, a weak preference for two, and no preference for one patient; primarily due to improved target dose coverage with the novel approach. Figure 1 illustrates the most pronounced example of improved target coverage with EQD2-based plan optimisation. The mean PTV D99% improved by 4.3Gy for EQD2-based plans compared to standard plans. The MDA was within 2mm for nearly all OAR; with the exception of the brachial plexus (average 4.6mm). Generally, EQD2-based plans were equally as robust as standard plans for uncertainties in dose mapping and α/β values: both sets of plans had brachial plexus doses out of tolerance on the robust dose summation for three patients, although this might partly be due to contouring variations. A single EQD2-based plan had proximal bronchial tree dose outside of tolerance by 1.8Gy on the robust summation.

Conclusion: