S1902
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
radiotherapy in localized prostate cancer. N Engl J Med. 2024 Oct 17;391(15):1413-1425. doi:10.1056/NEJMoa2403365.2. Le Guévelou J, et al. Urethra-sparing prostate cancer radiotherapy: Current practices and future insights from an international survey. Clin Transl Radiat Oncol. 2025;51:100907.3. Desai NB, et al. Prostate Oncologic Therapy While Ensuring Neurovascular Conservation (POTEN-C): A phase II randomized controlled trial of stereotactic ablative body radiotherapy (SAbR) with or without neurovascular sparing for erectile function preservation in localized prostate cancer. J Clin Oncol. 2020;38(6 Suppl):TPS381.
(Fig2a). Strategy 2 (Adapted Urethral Criteria): For cases where DIL PTV is overlapping with the urethra, and DIL V40Gy>95% cannot be achieved, a urethral dose-reduction technique will be used. The plan will be optimised to maintain DIL coverage of V40Gy>95%, while ensuring urethral D0.035cc < 40Gy. (Fig2b) New optimal dose guidance (V36Gy<0.1cc) is advised for the Bladder Trigone and NVB, as was achieved in 12/13 and 11/13 cases, respectively as shown in Fig1.
doi:10.1200/JCO.2020.38.6_suppl.TPS381 Keywords: SABR, Prostate, Urethral-sparing
Poster Discussion 2818 Real-time deep learning-based photon segment dose calculation Fan Xiao 1 , Niklas Wahl 2,3 , Claus Belka 1,4 , George Dedes 5,1 , Christopher Kurz 1 , Guillaume Landry 1,6 1 Department of Radiation Oncology, LMU University Hospital, Munich, Germany. 2 Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany. 3 National Center for Radiation Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany. 4 German Cancer Consortium (DKTK), a partnership between DKFZ and LMU University Hospital, Munich, Germany. 5 Department of Medical Physics, Ludwig-Maximilians-Universität München, Munich, Germany. 6 Bavarian Cancer Research Center (BZKF), Bavarian Cancer Research Center (BZKF), Munich, Germany Purpose/Objective: Fast and accurate dose calculation is essential for online re-optimization in adaptive radiotherapy and may foster real-time dose-guided radiotherapy [1]. Monte Carlo (MC) simulation remains the reference but is slow. Graphics Processing Unit (GPU) MC typically needs tens of seconds per plan to achieve high accuracy [2]. Deep learning (DL) methods can deliver sub-second level segment and seconds level plan dose calculation. Two coordinate paradigms exist: Beam’s Eye View (BEV) [3] and patient coordinates [4]. We present a comparative study of coordinate paradigms and representative models using the same dataset and pipeline, and introduce two lightweight models for fast photon dose calculation. Material/Methods: Planning CT and Volumetric Modulated Arc Therapy (VMAT) plans from 19 prostate cancer patients were collected. CT images were resampled to 3 × 3 × 3 mm3, and MC dose simulations were performed with a dose
Conclusion: A two-strategy approach for urethral-sparing in the INSPIRE trial maintains urethral dose ALARA without applying unachievable dose-limiting criteria and maintains priority to DIL coverage. Sexual potency preservation will be studied in the trial for eligible patients. References: 1. van As N, et al. Phase 3 trial of stereotactic body
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