ESTRO 2023 - Abstract Book

S764

Monday 15 May 2023

ESTRO 2023

geometrical overlap of the irradiated volumes?; Q2: Is there a concern for toxicity from the cumulative doses?; Q3: Are the target volumes of current and previous RT located in the same organ? The EORTC RP-2011 ReCare cohort will include patients with re-RT to a prescription dose or mean GTV dose of at least 50 Gy (EQD2). EBRT (photons, electrons, particles) and brachytherapy are allowed. The first phase (target accrual n=500) will include thoracic, abdominal and pelvic re-RT. Quality of life and treatment decision agreement will be evaluated as patient reported outcomes. Conclusion We propose a universally applicable consensus definition of re-RT and standardised nomenclature for scenarios of repetitive RT that do not fulfil the criteria for re-RT. This will foster harmonised reporting in clinical trials, with first clinical implementation in the EORTC RP-2011 ReCare cohort. OC-0918 Re-irradiation in clinical practice: international patterns of care survey endorsed by ESTRO/EORTC J. Willmann 1 , A.L. Appelt 2 , P. Balermpas 3 , B.G. Baumert 4 , D. de Ruysscher 5 , M. Hoyer 6 , C. Hurkmans 7 , O. Kaidar-Person 8 , I. Meattini 9 , M. Niyazi 10 , P. Poortmans 11 , N. Reynaert 12 , Y. van der Linden 13 , C. Nieder 14 , N. Andratschke 3 1 Paul Scherrer Institute, Center for Proton Therapy, Villigen, Switzerland; 2 University of Leeds, Leeds Institute of Medical Research at St James’s, Leeds, United Kingdom; 3 University Hospital Zurich, Department of Radiation Oncology, Zurich, Switzerland; 4 Cantonal Hospital Graubünden, Institute of Radiation-Oncology, Chur, Switzerland; 5 Maastricht University Medical Center, Department of Radiation Oncology (Maastro Clinic), Maastricht, The Netherlands; 6 Aarhus University Hospital, Danish Centre for Particle Therapy, Aarhus, Denmark; 7 Catharina Hospital Eindhoven, Department of Radiation Oncology, Eindhoven, The Netherlands; 8 Sheba Medical Center, Breast Cancer Radiation Therapy Unit, Ramat Gan, Israel; 9 Azienda Ospedaliero Universitaria Careggi, Radiation Oncology Unit, Oncology Department, Florence, Italy; 10 University Hospital, LMU Munich, Department of Radiation Oncology, , Munich, Germany; 11 Iridium Netwerk, Department of Radiation Oncology, Wilrijk-Antwerp, Belgium; 12 Institut Jules Bordet, Department of Medical Physics, Brussels, Belgium; 13 Leiden University Medical Centre, Department of Radiotherapy, Leiden, The Netherlands; 14 Nordland Hospital Trust, Department of Oncology and Palliative Medicine, Bodø, Norway Purpose or Objective The use of re-irradiation is increasing, propelled by the introduction of new radiation therapy (RT) techniques. However, high-level evidence to guide clinical practice is scarce. Thus, we investigated international patterns of care of re-irradiation (reRT), presenting hereby the thoracic indications. Materials and Methods We conducted an online survey from March to September 2022. The survey was endorsed by the European Organisation for Radiotherapy and Oncology (ESTRO) and the European Organisation for Research and Treatment of Cancer (EORTC) and distributed to radiation/clinical oncologists, as well as on social media (e.g., Twitter). The survey was split into five sections according to anatomical regions. Participants answered the sections matching their clinical focus. Each section included 14 multiple-choice questions, covering distinct parts of the reRT workflow, including indications, planning & delivery techniques, and follow-up. Percentages in the following refer to the total number of participants answering each question. Results The survey was completed by 371 respondents from 55 countries on 6 continents (Figure 1). Most respondents were from Italy (n=37, 10%), Spain (n=27, 7%), Germany (n=24, 6%) and the Netherlands (n=23, 6%). The median years of experience in radiation oncology were 17 (range 2-46). Most respondents (n=224, 60%) were affiliated with University Hospitals. Brain (78%), pelvis (66%) and the head and neck region (64%) were the most commonly treated anatomical regions (Figure 2A). The vast majority of respondents did not have institutional guidelines for re-irradiation (range among anatomical regions: 16-18%) (Figure 2B). After re-irradiation, most have their patients primarily followed-up by a radiation oncologist, with standard follow-up per the respective disease (range among anatomical regions: 54-70%) (Figure 2C). Follow-up schedules specific for re-irradiation are uncommon (range among anatomical regions: 6-8%)

Conclusion Re-irradiation is applied in all anatomical regions - most frequently in the brain, pelvis and head and neck region. However, most departments do not have internal guidelines, likely reflecting the lack of standardization and high-quality evidence to inform clinical practice. While re-irradiation specific follow-up is uncommon, in most practices patients are followed-up primarily by a radiation oncologist, which may be beneficial to assess the response to and potential side effects of re irradiation.

OC-0919 Stereotactic reirradiation:toxicity profile results from a phase I dose escalation study (Destroy-1)