ESTRO 2025 - Abstract Book

S244

Brachytherapy - Gynaecology

ESTRO 2025

Purpose/Objective: A tri-objective optimization model in BRIGHT was introduced for cervical cancer BT planning, which results in multiple high-quality plans representing different trade-offs in optimizing target doses and sparing organs-at-risk (OAR). We conducted a retrospective validation study evaluating its usage and quality compared to current clinical practice. Material/Methods: The first two objectives concern target coverage and OAR sparing aims according to the EMBRACE-II protocol, whereas the third objective includes added aims which were tuned with local BT teams [1]. Further, a constraint was incorporated to ensure one contiguous 250%-isodose volume. BRIGHT was run for 3.7 minutes, optimizing 260,000 dose calculation points. Final results were evaluated on 500,000 points. BRIGHT does not rely on clinical plan information, making our results applicable and reliable in clinical real-world settings. The first fraction of ten patients, treated in 2023-2024 using four HDR BT fractions of 7Gy, were included. The clinically used plans were generated by manually modifying dwell weights of a default loading pattern using Oncentra Brachy (Elekta). For planning with BRIGHT, a multi-disciplinary BT team used a custom-developed graphical user interface (GUI) to navigate the set of BRIGHT plans and select one. If desired, the chosen plan could then be adjusted. The resulting BRIGHT plan was displayed alongside the clinically used plan using the GUI shown in Figure 1, in a blinded observer study involving three radiation oncologists. They were independently asked to choose their preferred plan, and indicate strong, weak, or no preference, regarding EMBRACE-II DVH planning aims, visual inspection of the dose distribution, and overall plan choice. Additionally, they assessed whether the differences between the plans were clinically relevant. Finally, they evaluated for each plan separately whether they would use it to treat the patient.