S52
Brachytherapy - Gynaecology
ESTRO 2026
Candidate IS catheters were interpolated from applicator slots in the clinical plan to the most distant target contours while maintaining safe OAR margins. Automated IS catheter selection aiming to maximise geometric target coverage was performed using integer linear programming [2]. Treatment plans were generated for these configurations in compliance with EMBRACE II guidelines using BiCycle autoplanning, assuming three equal BT fractions and 25 × 1.8 Gy EBRT [3]. Plans for four catheter configurations with identical IC components and catheter numbers were compared: (i) manually selected, i.e., clinically used, applicator-guided parallel and oblique catheters (TPClin); and (ii-iv) automatically selected applicator- guided parallel (TPP), parallel and oblique (TPP&O), and applicator- plus template-guided catheters (TPP&O+T). For five patients with larger CTVHR, configurations with varying catheter numbers were compared on target coverage and OAR sparing indices (normalised; ≥ 1 means soft planning aims met). Results: Median (interquartile range) CTVHR volume was 37 (28-46) cm3 for the20 patients, and 46 (45-49) cm3 for the subset of 5 patients. Automated preprocessing and catheter generation/selection took under 1 minute, with BiCycle planning less than 10 minutes. Summed over 20 patients, 87/7/0, 90/0/0, 79/15/0, and 54/4/36 P/O/T catheters were selected for the Clin, P, P&O, and P&O+T configurations, respectively. Treatment plans of automatically generated configurations were non-inferior to those clinically used, with P&O or P&O+T configurations resulting in reduced bladder D2cm3, and P&O or P configurations showing improved CTVIRD98 (Figure 1). For the 5 highest CTVHR volume cases, plans based on automatically generated P&O and P&O+T configurations maintained target coverage and OAR sparing across the range of catheter numbers (Figure 2).
Conclusion: The total lead time to first irradiation was on average 313 minutes, with patient recovery, segmentation, and treatment planning being the most time-consuming tasks. Differences in patient recovery, MRI access, fractionation schedule, and overnight hospital stay were associated with variation in total lead time across centers. Keywords: cervical cancer, brachytherapy workflow, timing Digital Poster 1228 Fast automated catheter configuration planning in intracavitary/interstitial cervical cancer brachytherapy Robin Straathof 1 , Sharline M. van Vliet-Pérez 1 , Jenny Dankelman 2 , Ben J.M. Heijmen 1 , Henrike Westerveld 1 , Remi A. Nout 1 , András Zolnay 1 , Linda Rossi 1 , Inger- Karine K. Kolkman-Deurloo 1 , Nick J. van de Berg 1 1 Radiotherapy, Erasmus MC Cancer Institute, University Medical Centre Rotterdam, Rotterdam, Netherlands. 2 BioMechanical Engineering, Delft University of Technology, Delft, Netherlands Purpose/Objective: Determining an optimal intracavitary/interstitial (IC/IS) brachytherapy (BT) implant configuration for locally advanced cervical cancer patients can be a complex and labour-intensive task, motivating the development of automated strategies [1]. In this work, we propose a fast, decoupled approach to support clinicians in pre- planning IC/IS implants of varying complexity, including parallel, oblique and template-guided catheters. Material/Methods: Our approach separates geometry-based configuration selection from dose optimisation. First fraction plans from 20 patients treated with the Venezia IC/IS applicator (Elekta AB) were obtained.
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