ESTRO 2025 - Abstract Book

S1842

Clinical – Upper GI

ESTRO 2025

3718

Digital Poster Findings of the PROTIEUS trial pre-accrual quality assurance contouring assessment – the importance of the benchmark case Fiona Williams 1 , Sarah Gwynne 1,2 , Jonathan Helbrow 1,2 , Geraint Lewis 3 , Owen Nicholas 1 , Ganesh Radhakrishna 4 , Claire Harrison 5 , Betsan Thomas 6 , Temi Adedoyin 7 , Natasha Hava 7 , Memuna Rashid 7 , Alan Sahin 7 , Maria Hawkins 8 1 Clinical Oncology, South West Wales Cancer Centre, Swansea, United Kingdom. 2 National RTTQA Group, Mount Vernon Cancer Centre, Northwood, United Kingdom. 3 Medical Physics, Velindre University NHS Trust, Cardiff, United Kingdom. 4 Clinical Oncology, Christie NHS Foundation Trust, Manchester, United Kingdom. 5 Clinical Oncology, Northern Ireland Cancer Centre, Belfast, Ireland. 6 Clinical Oncology, Velindre University NHS Trust, Cardiff, United Kingdom. 7 Cancer Research UK, UCL Cancer Trials centre, London, United Kingdom. 8 Department of Medical Physics & Biomedical Engineering, University College London Hospital, London, United Kingdom Purpose/Objective: PROTIEUS is a UK phase 2 RCT comparing proton and photon pre-operative chemoradiotherapy in oesophageal cancer. The pre-accrual stage of trial QA ensures quality of RT across centres, prior to the start of the trial. Here we present the findings of the PROTIEUS benchmark case contouring QA, highlighting areas of variation to inform future learning. Material/Methods: Clinicians who expressed interest in recruiting to PROTIEUS were asked to undertake the benchmark case, unless pre-approved for 4DCT in PROTIEUS, from prior approval from SCOPE 2. Those not pre-approved were asked to delineate CTVB, ITV and PTV (described in table 1), for a T4a (right pleura) N1M0 gastro-oesophageal junction case, using the RT planning guidance document (RPGD). GTV and CTVA were pre-delineated. Each domain (CTVB length, CTVB editing for normal structures, CTVB ELNI (elective lymph node irradiation), ITV and PTV) compared against a reference volume and classified as per the Global Harmonisation Group criteria: acceptable per-protocol (APP), acceptable variation (AV) and unacceptable variation (UV), using pre-defined, trial specific criteria (1). If submission considered overall unacceptable, a satisfactory resubmission was required for approval to recruit. 4 members of the TMG were responsible for the reviews.