S2775
RTT - RTT contouring, target definition, and treatment planning
ESTRO 2026
5 Department of Radiation Oncology, Princess Alexandra Hospital, Brisbane, Australia. 6 Medical School, University of Queensland, Brisbane, Australia. 7 Department of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, Australia. 8 Sir Peter MacCallum Department of Oncology, The Unviersity of Melbourne, Melbourne, Australia. 9 Department of Radiation Oncology, Wellington Blood and Cancer Centre, Wellington, New Zealand. 10 Adem Crosby Cancer Centre, Sunshine Coast University Hospital, Birtinya, Australia. 11 School of Medicine & Dentistry, Griffith University, Brisbane, Australia. 12 Department of Radiation Oncology, Calvary Mater Hospital, Newcastle, Australia. 13 School of Medicine, University of Sydney, Sydney, Australia. 14 Canterbury Regional Cancer and Haematology Service, Christchurch Hospital, Christchurch, New Zealand. 15 Department of Medicine, University of Otago, Christchurch, New Zealand. 16 Department of Radiation Oncology, Chris O’Brien Lifehouse, Camperdown, Australia. 17 Regional Cancer and Blood Service, Auckland City Hospital, Auckland, New Zealand. 18 Crown Princess Mary Cancer Centre, Westmead Hospital, Westmead, Australia. 19 Department of Radiation Oncology, Shoalhaven Cancer Care Centre, Nowra, Australia. 20 Northern Sydney Cancer Centre, Royal North Shore Hospital, St. Leonards, Australia. 21 Radiation Therapy Quality Assurance, Trans-Tasman Radiation Oncology Group, Waratah, Australia. 22 NHMRC Clinical Trials Centre, University of Sydney, Sydney, Australia. 23 Cancer Care Centre, St George Hospital, Kogarah, Australia. 24 Department of Medical Oncology, Nelune Cancer Centre, Prince of Wales Hospital, Randwick, Australia. 25 School of Clinical Medicine, University of NSW, Sydney, Australia. 26 Department of Radiation Oncology, Royal North Shore Hospital, St Leonards, Australia. 27 Faculty of Medicine and Health, University of Sydney, Sydney, Australia Purpose/Objective: MASTERPLAN (MFOLFIRINOX And Stereotactic Radiotherapy (SBRT) for Pancreatic Cancer With High Risk and Locally Advanced Disease; ACTRN12619000409178) is a randomised phase II trial evaluating whether adding SBRT to modern chemotherapy improves locoregional control in high- risk, borderline resectable and locally advanced pancreatic cancer (1). Due to the complexity of pancreatic SBRT, a comprehensive real-time radiation therapy quality assurance (RTQA) program was implemented for participants randomised to the SBRT arm. This analysis describes the RTQA methodology and outcomes. Material/Methods: Sites underwent mandatory pre-trial credentialing, including completing a SBRT facility questionnaire,
SBRT phantom dosimetry audit and a standardised benchmarking case. Sites followed published contouring (2), planning and delivery guidelines. On- trial RTQA included real-time review (RTR) of all SBRT plans assessing target delineation and dose distribution. Volumes and dosimetric targets for coverage and Organs at Risk (OARs) were categorised as Acceptable, Minor variation or Major variations. Feedback was provided via case reports including variation criteria, reviewer comments, screen captures, and DICOM structure sets. Results: 18 centres completed pre-trial credentialing; 13 recruited participants. 11(61.1%) sites passed benchmarking on the first attempt, and 7(38.9%) on the second. 5 cases required resubmission for target delineation, 2 for dosimetry. 50 participants were randomised to SBRT. 40(80%) initiated planning and underwent RTR. Of these, 28(70%) passed RT QA successfully on first attempt, and 12(30%) cases were required to be resubmitted with 9/12(75%) cases having major variations. 21/28(75%) plans passing on first submission had minor variations; 2(7.1%) cases had major protocol variations but were deemed clinically acceptable.11/12(91.7%) resubmissions were for contouring, 2(16.7%) were for dosimetry and 2(16.7%) for inadequate imaging, noting that some cases had more than one reason for resubmission. Upon final review, 9/12(75%) had minor protocol variations and the number of major variations reduced to zero. 10/12(83.3%) required one resubmission and 2(16.7%) required a second resubmission. 4(10%) cases requested an initial contour-only review, prior to planning. All required resubmission, with 2 requiring a second resubmission. A full list of protocol variations are outlined in Table 1. The most common OAR variation was duodenum (8 cases; 20%); for target volume, it was tumour vessel interface (TVI) (16 cases; 40%). Conclusion: Real-time RTQA was essential for ensuring high- quality, protocol-compliant pancreatic SBRT, with emphasis on target volume contouring.
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