ESTRO 2022 - Abstract Book

S568

Abstract book

ESTRO 2022

Results In the phantom study, the lateral beam penumbra was reduced by 2.6mm (from 10.3mm to 7.7mm). Furthermore, relevant reduction of dose to simulated OARs was observed. Reduction in mean dose to OARs was around 7% of the prescribed dose. Reduction in D1% ranged from 0% to 16% and was larger for the OARs at larger CTV-OAR distance. For all 3 clinical cases, CTV coverage remained comparable to the standard AA plan. The modified AA plans resulted in reduction of dose to all OARs (Fig 2) with the exception of small increase of D0.03cc to brainstem and skin. However, this increase was below 1.5Gy and remained within the OAR tolerance. For every patient, at least one OAR had dose reduction >2Gy. Volume of isodose 80% (normalized to CTV volume) decreased by 16%, 12% and 44% for patients 1, 2 and 3, respectively.

Conclusion This study presented a proof of concept describing the optimization of AA. The lateral dose fall-off was improved and led to clinically relevant reduction in OAR doses with preserved CTV coverage.