ESTRO 2022 - Abstract Book

S329

Abstract book

ESTRO 2022

Conclusion We have shown that muscle characteristics, collected from routine imaging, are a potential tool for predicting 90-day mortality for patients with lung cancer treated with radiotherapy. Model performance showed good accuracy with muscle area or density, with males showing greater impact of poor muscle condition on 90-day mortality. Muscle characteristics showed superior predictive performance over performance status. Further internal and external validation will be performed.

MO-0392 Inter-observer variation in a national lung SABR rollout program: Lessons learnt & future directions

P. Diez 1 , F. McDonald 2 , C. Brooks 1 , A. Haridass 3 , M. Hatton 4 , C. Peedell 5 , Y.M. Tsang 6 , J. Conibear 7

1 National Radiotherapy Trials Quality Assurance Group, Mount Vernon Cancer Centre, Radiotherapy Physics, Northwood, United Kingdom; 2 The Royal Marsden NHS Foundation Trust, Lung Unit, London, United Kingdom; 3 Clatterbridge Cancer Centre, Department of Clinical Oncology, Liverpool, United Kingdom; 4 Weston Park Hospital, Department of Clinical Oncology, Sheffield, United Kingdom; 5 South Tees NHS Foundation Trust, Department of Clinical Oncology, Middlesbrough, United Kingdom; 6 National Radiotherapy Trials Quality Assurance Group, Mount Vernon Cancer Centre, Radiotherapy Department, Northwood, United Kingdom; 7 Barts Cancer Centre, Radiotherapy Department, London, United Kingdom Purpose or Objective A radiotherapy quality assurance (QA) program was developed as part of a national plan for the expansion of lung stereotactic ablative body radiotherapy (SABR) services. The aim was to ensure consistent, high-quality SABR was implemented across all centres introducing this technique. As part of the QA program, radiation oncologists’ ability to delineate target volumes and associated organs at risk (OARs), according to UK SABR Consortium Guidelines and Global Harmonization Group Consensus Guidelines (Mir et al, 2020), was assessed. Materials and Methods A contouring benchmark case was circulated amongst 24 centres starting their lung SABR program. The 4DCT dataset sent contained 12 individual phases. A diagnostic PET-CT was also provided. Two clinicians from each hospital were invited to contour the ITV, PTV and 10 OARs following supplied guidance. All submissions were reviewed by a team of SABR experts comprising 5 radiation oncologists, a medical physicist and a clinical research fellow. Detailed feedback was provided through standardised written and pictorial reports and any unacceptable contours were asked to be resubmitted after further guidance from experienced mentors assigned through the implementation program. Consensus volumes were agreed by all reviewers. Acceptability criteria were defined for each structure based on cranio- caudal borders, axial under or over-contouring and inclusion/exclusion of anatomical features as detailed in the instructions. Results 44 radiation oncologists completed the benchmark case, only one was approved on the first attempt. Failed submissions had a median of 6 unacceptable structures (range 2-9). 52.3% of ITVs were found to be unacceptable, mostly due to under- contouring, however most PTVs (95.5%) had been grown correctly. 6/10 OARs had failure rates ≥ 50%, the brachial plexus