S728
Clinical – Lower GI
ESTRO 2026
MRI-only or CT-MRI) and cause of MRI-only pathway non-compliance data were recorded. Results: A significant mean reduction in PTV volume of 11% was found between CT-only (88.7cc) to MRI-only (78.8cc) pathways. MRI-only planning resulted in small, clinically insignificant differences in dose parameters for target volumes and OARs.Since 1st April 2025,149 patients were treated with hypo-fractionated prostate radiotherapy. 89.3% were treated MRI-only, 6.0% were treated CT-MRI and 4.7% were treated CT-only. CT-only treatments were all due to MRI contra-indications, CT- MRI treatments were due to MRCAT failure in 2/9 cases and MRCAT ineligibility in 7/9 cases (x3 artificial hip, x3 body size, x1 metalwork). Conclusion: MRI-only planning for hypo-fractionated prostate treatments can successfully be delivered in ~90% of all cases, enabling significant equipment efficiency savings. MRI-only planning resulted in mean target volume reductions of ~10%, which may have a clinically significant impact on patient toxicity, and can be considered clinically equivalent to CT-only planning in terms of planned doses to the target volumes and OARs. Keywords: MRI-only, impact, efficiency First implementation of an All-in-One solution with full automatic workflow for rectal cancer based on an integrated CT-linac Luqi Wang 1 , Xuemin Li 1 , Mengying Yang 2 , Yuxi Pan 1 , Mingqing Wang 1 , Wei Zhang 2 , Lecheng Jia 2 , Hao Wang 1 1 Radiation Oncology, Peking University Third Hospital, Beijing, China. 2 RT BU, Shanghai United Imaging Healthcare Co., Ltd., Shanghai, China Purpose/Objective: To prospectively evaluate the feasibility, clinical workflow efficiency, and dosimetric performance of an integrated All-in-One (AIO) radiotherapy solution for rectal cancer, combining CT simulation, automatic segmentation, planning, and treatment on a single CT- linac platform. Material/Methods: Digital Poster 3816 A total of 20 patients with rectal cancer underwent AIO radiotherapy using an integrated CT-linac system. The workflow included CT simulation, AI-based auto- segmentation, plan generation, online verification, and beam delivery—all executed sequentially without patient repositioning. Dosimetric parameters for targets and organs-at-risk (OARs), as well as gamma analysis results, were collected. Auto-segmentation accuracy was evaluated using Dice similarity coefficient (DSC) and average surface distance (ASD).
79.2% (19/24) and 59.3% (16/27) in SCRT and LCRT arms, respectively. Organ preservation rates were 66.7% (16/24) and 51.9% (14/27). Grade 3–4 adverse events occurred in 8.3% (2/24) of patients in SCRT arm and 14.8% (4/27) in LCRT arm, all due to thrombocytopenia. Conclusion: We present the first study comparing two neoadjuvant strategies (± PD-1 inhibition) for intentional OP in early low rectal cancer. Both demonstrated favorable efficacy, with final comparative outcomes pending trial enrollment and further follow-up. Keywords: Radiotherapy, Immunotherapy, early rectal cancer Digital Poster 3751 The clinical impact of MRI-only planning on a hypo- fractionated prostate treatment pathway Danielle Eden 1 , Chloe Pratt 1 , Anna K Clark 1 , Christopher O'Hara 1 , Sarah Wright 1 , Ann Henry 2 , Bashar Al-Qaisieh 1 , Richard Speight 1 , David Bird 1,2 1 Department of Medical Physics, Leeds Cancer Centre, Leeds, United Kingdom. 2 Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom Purpose/Objective: Magnetic Resonance Imaging (MRI)-only radiotherapy planning is becoming more common for prostate treatments due to improved prostate visualisation and workflow efficiency benefits compared to CT-MR fusion pathways. This study aimed to establish the clinical impact of MRI-only planning for hypo- fractionated prostate treatments through 1) comparing target volume and dose parameters between CT-only and MRI-only treatments and 2) determining workflow efficiency savings by assessing the MRI-only pathway success rate. Material/Methods: Planning data for consecutively treated CT-only and MRI-only patient cohorts of hypo-fractionated (36.25 Gray in 5 fractions) prostate only treatments were retrospectively collected from a single centre. The CT- only cohort (230 patients – randomly selected) treated between 2020 and 2025 and MRI-only cohort (78 patients – all treated patients) treated between April and August 2025 followed the same outlining and planning protocol with respect to target volume delineation and plan optimisation. The MRI-only pathway used the Philips MRCAT Pelvis synthetic-CT model for dose planning and a registered T2w MRI for target delineation. Plan target volumes (PTVs) and target/OAR dose parameters were compared between cohorts using paired t-tests.All patients undergoing hypo-fractionated prostate radiotherapy since 1st April 2025 were reviewed. Pathway outcome (CT-only,
Made with FlippingBook - Share PDF online