ESTRO 2023 - Abstract Book

S325

Sunday 14 May 2023

ESTRO 2023

improving patient tumour control and quality of life outcomes. Here we present the early experience of ICR submission, exploring number of cases submitted, ICR outcomes, and any patterns in causes of non-compliance. Materials and Methods Radiotherapy guidelines for each individual trial define the specific data upload requirements for an effective ICR. DICOM diagnostic and planning images, structure sets, plan, and dose files are uploaded to the QUARTET web-based platform where they are processed and sent for review. Expert clinicians and physicists perform a plan evaluation against protocol requirements. Possible evaluation outcomes are: Per Protocol, Acceptable Variation, Unacceptable Variation, or Justified Variation. All ICR submissions and outcomes are tracked for individual trials; submissions between 01/05/2016 and 09/10/2022 were collated and analysed for the purpose of this report. Results For six QUARTET-affiliated trials, a total of 255 cases from 15 countries have been submitted to the platform for ICR. ICRs have been completed prospectively for 125 patients. retrospectively for 119 patients, and 11 further reviews are underway. Figure 1 demonstrates the increasing number of submissions over time, with the rising number and proportion of prospective plan reviews. The total, initial plan rejection rate is 97/243 cases (39.9%), however, it should be noted that this varies significantly depending on the trial/tumour site complexity. Proportion of plan rejections are broadly similar between prospective and retrospective case reviews (39.2% v 40.7%) but again vary by trial. The main singular cause of plan rejection is target delineation (22%), however 80% of plan rejections have at least two protocol violations (also see Figure 2). Unacceptable dose variations are more often associated with retrospective reviews due to propagation of error from incorrect (target) delineation.

Conclusion There is clear indication of planning variations in paediatric radiation oncology. Despite comprehensive RTQA guidelines, a significant number of plan rejections occur. This preliminary report underlines the importance of prospective plan review. QUARTET will continue to provide RTQA for paediatric clinical trials in Europe and expand education and practice-sharing initiatives to better support institutions to produce high-quality treatment plans, benefitting those participating and outside of clinical trials. OC-0423 Critical role of QA in a national SBRT rollout program for pelvic & lower abdominal oligometastases P. Diez 1 , C. Brooks 1 , A. Tree 2,3 , M. Hatton 4 , A. Haridass 5 , N. van As 2,6 , E.M. Dunne 7 , J. Conibear 8 , K. Aitken 9,2 , R. Muirhead 10 , C. Peedell 11 , F. McDonald 12 1 National Radiotherapy Trials Quality Assurance Group, Mount Vernon Cancer Centre, Radiotherapy Physics, Northwood, United Kingdom; 2 Institute of Cancer Research, Division of Radiotherapy and Imaging, Sutton, United Kingdom; 3 The Royal