ESTRO 2025 - Abstract Book

S348

Brachytherapy - Physics

ESTRO 2025

Results:

The dose difference between summations using brachytherapy PD and BED was most pronounced in HR-PTV (median D95 16.4 Gy; range 1.3-23.3 Gy) compared to LR-PTV (median D95 6.4 Gy; range 0-14.9 Gy). HR-PTV BED median D95 was 55.1 Gy (54.2-61.4) whereas HR-PTV PD median D95 was 71.5 Gy (62.8-79.5). LR-PTV BED median D95 was 45.8 Gy (43.9-48.1) and LR-PTV PD median D95 was 52.4 Gy (45.4-58.9). Conclusion: In this retrospective analysis of GBM patients receiving EBRT after GammaTile® brachytherapy, brachytherapy BED and PD combined with external radiation doses showed greater difference within HR-PTV, the junction zone of dose overlap, than in LR-PTV, where tissue receives lower dose from GammaTile brachytherapy. Without BED correction, using PD for planning could potentially underdose areas at high risk of recurrence.

Keywords: Gamma Tile, Glioblastoma, EBRT boost

3357

Digital Poster Commissioning a treatment planning system for a novel treatment, diffusing alpha-emitters radiation therapy Zach Hollis, Magdalena Klodowska, Li Tee Tan, Diane Whitney Medical Physics, Cambridge University Hospitals, Cambridge, United Kingdom Purpose/Objective: Diffusing alpha-emitters radiation therapy (DaRT) is an emerging treatment which combines the destructive power of alpha particles with the physical advantages of interstitial brachytherapy. The Alpha DaRT device, manufactured by Alpha Tau Medical Ltd., comprises radioactive sources (hollow tubes coated with a layer of Ra-224) which are inserted into tumours using dedicated applicators. The decay of Ra-224 within tumour tissue releases short-lived alpha-emitting atoms which disperse by diffusion, resulting in a diffusion zone around each source of ~5mm in diameter. In normal tissue, the different vasculature characteristics limits the diffusion zone around implanted sources to <2mm resulting in a complete absence of ≥G3 acute or late toxicities in patients treated so far [1].