ESTRO 2023 - Abstract Book

S500

Sunday 14 May 2023

ESTRO 2023

Conclusion A trained dose engine was implemented, delivering fair accuracy at strongly reduced computation times. Further developments will aim to reach stricter tolerances. This will support the development of real-time online correction strategies. OC-0615 Variations in cumulative dose assessment in re-irradiation scenarios: a multi-centre evaluation N. Hardcastle 1 , E. Vasquez Osorio 2 , C. Mayo 3 , A. Jackson 4 , F. Belosi 5 , M. Chamberlain 5 , C. Thompson 6 , C. Palmer 7 , N. Solomou 7 , L. Hoffmann 8 , P. Dupuis 9 , M. Ayadi 9 , S. Muscat 10 , J. Handley 11 , A. Selby 12 , H.S. Rønde 13 , N. West 14 , A. Aarberg 15 , T. Skopidou 16 , J. Stroom 17 , J. Perez-Alija 18 , M. Popovic 19 , C. Kelly 20 , C. Michailidou 21 , A. Appelt 22 1 Peter MacCallum Cancer Centre, Physical Sciences, Melbourne, Australia; 2 University of Manchester, Division of Cancer Sciences, Manchester, United Kingdom; 3 University of Michigan, Department of Radiation Oncology, Ann Arbor, USA; 4 Memorial Sloan Kettering Cancer Centre, Department of Medical Physics, New York, USA; 5 University Hospital, Zurich, Department of Radio-Oncology, Zurich, Switzerland; 6 Leeds University Teaching Hospital, Medical Physics, Leeds, United Kingdom; 7 Norfolk and Norwich University Hospital, Medical Physics, Norwich, United Kingdom; 8 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; 9 Centre Léon Bérard, Medical Physics, Lyon, France; 10 Queen Alexandra Hospital, Medical Physics, Portsmouth, United Kingdom; 11 The Christie Hospital, Medical Physics, Manchester, United Kingdom; 12 South West Wales Cancer Centre, Medical Physics, Swansea, United Kingdom; 13 Aarhus University Hospital, Danish Centre for Particle Therapy, Aarhus, Denmark; 14 Northern Centre for Cancer Care, Medical Physics, Newcastle, United Kingdom; 15 Haukeland University Hospital, Medical Physics, Bergen, Norway; 16 Guy's and St Thomas' NHS Foundation Trust, Medical Physics, London, United Kingdom; 17 Champalimaud Foundation, Department of Radiation Oncology, Lisboa, Portugal; 18 Hospital de la Santa Creu i Sant Pau, Medical Physics, Barcelona, Spain; 19 McGill University Hospital, Medical Physics Unit, Montréal, Canada; 20 St Luke's Radiation Oncology Network, Medical Physics, Dublin, Ireland; 21 Michailidou, Medical Physics, Agios Athanasios, Cyprus; 22 University of Leeds, Leeds Institute of Medical Research at St James's, Leeds, United Kingdom Purpose or Objective Assessment of cumulative doses to organs at risk (OARs) across multiple treatments is critical to safe re-irradiation, however there are multiple pathways to perform this assessment. We performed a multi-centre study to quantify the impact of clinical pathways on assessment of cumulative dose to OARs. Materials and Methods We provided DICOM planning CT, structures and dose for original and re-treatment courses for two patients with head & neck (HN) and lung cancer (Figure 1). Participants determined and reported cumulative physical and EQD2 doses (near- maximum, volumetric dose) to OARs using their clinical process and software. Standardised α / β values were provided for EQD2 calculation, and description of dose summation pathway was collected via a survey. Participants were asked to (optionally) submit physical dose distributions from the original course mapped onto the re-treatment course CT. A consistent workflow by one observer in a single software was used to sum the submitted registered dose distributions with dose from the second course dose, to assess isolated variation in image registration for dose mapping.