S1511
Interdisciplinary - Quality assurance and risk management
ESTRO 2026
Digital Poster 2167 Pancreas Radiotherapy Quality Assurance: Benchmark vs Clinical Contouring Performance in SCALOP2 Nicholas A Gomez 1 , Sarah H Gwynne 1,2 , Maria Hawkins 3 , Jonathan Helbrow 4 , Somnath Mukherjee 5 , Philip Parsons 6 , Ganesh Radhakrishna 7 , Owen Nicholas 1,2 1 Department of Oncolgy, South West Wales Cancer Centre, Swansea, United Kingdom. 2 Faculty of Medicine, Health and Life Science, Swansea University, Swansea, United Kingdom. 3 Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom. 4 Department of Oncology, Gloucestershire Hospitals NHS Foundation Trust, Cheltenham, United Kingdom. 5 Department of Oncology, Oxford Cancer Centre, Oxford, United Kingdom. 6 Medical Physics Department, Velindre Cancer Centre, Cardiff, United Kingdom. 7 Department of Oncology, The Christie Hospital, Manchester, United Kingdom Purpose/Objective: SCALOP-2, a UK chemoradiotherapy (CRT) trial for locally advanced pancreatic cancer (LAPC), evaluated dose-escalated CRT and concurrent radiosensitisation with nelfinavir. Mandatory participation in the national radiotherapy trials quality assurance (RTTQA) programme ensured protocol compliance across centres. This analysis compares contouring protocol compliance at pre-accrual and on-trial individual case review (ICR), to assess RTQA impact. Material/Methods: During pre-accrual, principal investigators (PIs) completed a contouring benchmark exercise using anonymised CT datasets, clinical details, and a radiotherapy planning guidance document, detailing target volume and organ of interest contouring instructions. Contours were compared against predefined reference volumes, generated by 3 oncologists on the trial management group. For ICR, prospective reviews (PRs) were performed on all patients in stage 1. In stage 2, PRs were planned for first standard dose arm and high dose arm submissions. Timely retrospective reviews (TRRs) were intended on contours that didn’t undergo PR. Submitted contours were qualitatively assessed as acceptable, acceptable variation (AV) or unacceptable variation(UV). Identification of UVs necessitated resubmission. Radiologist involvement in contouring was recorded.Qualitative and quantitative differences in UV rates between pre-accrual and ICR were evaluated and statistical significance was assessed using a two-proportion z-test (p<0.05). Results: 26 pre-accrual contours from 23 centres were
Conclusion: The evidence base used for reRT dose constraints is limited. Although the characteristics of randomised controlled trials (RCTs) in the reRT setting has been explored [3], none of the RCTs included in the systematic review focussed on pelvic sites. The average evidence score across references was low (0.44), and most evidence categories, including those most relevant to reRT decision-making, scored < 0.40. The other references either concerned first course constraints or were review/consensus papers. These weak and inconsistent sources likely contribute to the significant inter-centre variation in practice. Improved prospective data collection, standardised reporting and education are needed to enable reproducibility, data pooling and the development of more reliable reRT dose constraints. References: [1] Stroom J, et al. Reirradiation dose constraints in clinical practice: Results of an international survey. Radiother Oncol. 2025 Sep;210:111030. doi: 10.1016/j.radonc.2025.111030. Epub 2025 Jul 14. PMID: 40669609.[2] Guyatt GH, et al. BMJ. 2008 Apr 26;336(7650):924-6. doi: 10.1136/bmj.39489.470347.AD. PMID: 18436948; PMCID: PMC2335261.[3] Beddok A, et al. Reirradiation: Standards, challenges, and patient-focused strategies across tumor types. CA Cancer J Clin. 2025 May 29. doi: 10.3322/caac.70016. Epub ahead of print. PMID: 40438993. Keywords: reirradiation, dose constraints, evidence quality
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