ESTRO 2020 Abstract book

S433 ESTRO 2020

The patterns of practice for adaptive and real-time radiation therapy (POP-ART RT) study aims to determine to which extent and how these methods are used in clinical practice and to understand the barriers to implementation. Here we report on part I: real-time respiratory motion management (RRMM). Material and Methods An institution-specific questionnaire developed during the 2 nd ESTRO physics workshop was distributed worldwide. The focus was both on current practice and wishes for implementation. Therefore, centres not (yet) doing RRMM were encouraged to participate. RRMM was defined as the use of gating in free-breathing (FB) or breath-hold (BH), or tracking if the beam is continuously realigned with the target in real-time (via robotic or gimbal guidance, MLC or couch tracking). Respondents were asked if they used RRMM for selected tumor sites, the percentage of patients treated with RRMM, eligibility criteria and the monitoring signal used to guide gating or tracking. Respondents were also asked if they wished 1) to change or expand their use of RRMM for a tumor site already treated with RRMM and 2) to implement RRMM for a new tumor site and to rank the barriers to implementation in order of importance. Results The questionnaire was filled out by 200 centres from 41 countries. 68% of respondents used RRMM in at least one tumor site (“users”). Inspiration BH was the dominant technique for breast and lymphoma, whereas the spread in technique was greater for other sites (Table 1). Within any given tumor site, users only applied RRMM in a subset of patients. The most frequently selected percentage range of patients treated using RRMM was <25% for lung, pancreas and lymphoma, 25-50% for breast and >75% for liver. However, for liver and pancreas, >50% of users applied RRMM in >50% of patients. The main selection criteria was “left breast” (76%) for breast and SBRT (~50%) for lung, liver and pancreas. Across all tumor sites, external marker was the main RRMM signal used by >60% of respondents. For breast and lymphoma this was followed by surface imaging and breathing volume. KV/MV imaging was frequently used for liver and pancreas (with markers) and for lung (with or without markers) (Fig 1a). Tracking was mainly done on robotic linacs with hybrid monitoring. For breast and lung, 36% and 49% of the centres respectively wish to expand or implement RRMM (Fig 1b). In contrast, for liver and pancreas >55% of centres do not use RRMM and do not wish to implement it. Overall 71% of centres wish to implement RRMM for any new treatment site (Fig 1c) but human/financial resources and capacity on machine were the main barriers (Fig 1d-e).

Conclusion For the first time, a correlation of patient outcome in respect to plan robustness has been performed for skull base tumors. Our results show that, for this cohort of patients, LF does not correlate with lack of plan robustness, indicating that our planning approach is robust. On the other hand, the analysis of dosimetric parameters seems to indicate that local failures are associated with a reduction of target coverage in the nominal plan, indicating that the dosimetric quality of the nominal plan is of most importance for obtaining tumor control. (1) Albertini et al, PMB, 2011 (2) Lowe et al, PMB, 2016 OC-0703 Patterns of practice for adaptive and real- time radiation therapy: part I intra-fraction motion G. Distefano 1 , J. Bertholet 2 , P. Poulsen 3 , T. Roggen 4 , C. Garibaldi 5 , N. Tilly 6 , J. Booth 7 , U. Oelfke 8 , B. Heijmen 9 , M. Aznar 10 1 St. Luke's Cancer Centre Royal Surrey County Hospital, Radiotherapy Physics, Guildford, United Kingdom ; 2 The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, Joint Department of Physics-, London, United Kingdom ; 3 Aarhus University Hospital, Department of Oncology and Danish Center for Particle Therapy, Aarhus, Denmark ; 4 Varian Medical Systems Imaging Laboratory GmbH, Applied Research, Dättwil AG, Switzerland ; 5 European Institute of Oncology IRCCS, IEO- Unit of Radiation Research, Milan, Italy ; 6 Elekta Instruments AB and Uppsala University, Medical Radiation Physics- Department of Immunology- Genetics and Pathology, Uppsala, Sweden ; 7 Royal North Shore Hospital and University of Sydney, Northern Sydney Cancer Centre and Institute of Medical Physics, St.Leonards and Camperdown, Australia ; 8 The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, Joint Department of Physics, London, United Kingdom ; 9 Erasmus MC Cancer Institute, Department of Radiation Oncology, Rotterdam, Netherlands Antilles ; 10 School of Medical Sciences- Faculty of Biology- Medicine and Health The University of Manchester, Division of Cancer Sciences, Manchester, United Kingdom Proffered Papers: Proffered papers 37: 4D and Adaptive RT

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