ESTRO 2025 - Abstract Book

S344

Brachytherapy - Physics

ESTRO 2025

Results: Figure 2 illustrates the sensitivity of treatment plans to simulated organ motion across different directions and magnitudes. A 10 mm deformation in P-A direction, resulted in a mean (SD) ΔD %/mm of 8.0 (4.0), 5.9 (2.3), and 4.4 (3.1) % for bladder, rectum, and bowel, respectively, consistent with previously reported data in the literature 1 . Assuming these values for all four HDR fractions, and 45 Gy EBRT for a plan reaching all EMBRACE-II dose objectives 2 , the total D 2cm3 dose in Gy EQD2 3 would increase by 5%, 3%, 2% per mm of organ movement in the case of unfavorable organ shifts for the bladder, rectum, and bowel, respectively. ΔD %/mm for other directions were between 1 and 4%.