ESTRO 2020 Abstract Book

S217 ESTRO 2020

Results Mean follow up was 70 months (4 - 256). The 120, 180 and 240 months LC rates were 79%, 77% and 77% and DFS rates were 58%, 56%, 56% respectively. We achieved a clinical and radiological complete response in 177 patients (95.5%). In 32 patients (18%) a second recurrence was identified and a third recurrence occurred in 12 patients (6.7%). 16 second relapses were retreated with further VBT and 6 achieved a new CR. Metastases rate was 29%. Treatment was well tolerated. Acute GU G1-G3 toxicity 21 cases (12.1%) and acute GI G1-G3 toxicity 21 cases (12.1%). The major pattern of late toxicity was G1-G3 vaginal stenosis (63 patients, 35.2%). Three developed necrosis of the mucosa (G4) of the inferior third of the vagina, resolved after medical therapy.

Poster Highlights: Poster highlights 14 PH: MRI only planning

PH-0406 An IPEM international survey of MRI use for external beam RT treatment planning R. Speight 1 , M. Tyyger 1 , M.A. Schmidt 2 , G.P. Liney 3 , R.I. Johnstone 4 , C.L. Eccles 5 , M. Dubec 6 , B. George 7 , A. Henry 1 , T. Nyholm 8 , F. Mahmood 9 , J. Korhonen 10 , R. Sims 11 , R.H.N. Tijssen 12 , F. Vanhoutte 13 , S. Busoni 14 , T. Lacornerie 15 , H. McCallum 16 1 Leeds Cancer Centre, Leeds Teaching Hospitals NHS Trust, Leeds, United Kingdom ; 2 Royal Marsden NHS Foundation Trust and Institute of Cancer Research, Cancer Research UK Cancer Imaging Centre, London, United Kingdom ; 3 Ingham Institute for Applied Medical Research, Liverpool Cancer Therapy Centre, Sydney, Australia ; 4 Guy’s and St. Thomas’ NHS Foundation Trust and University College London, Dept. of Computer Science, London, United Kingdom ; 5 The Christie NHS Foundation Trust and the University of Manchester, Radiotherapy, Manchester, United Kingdom ; 6 The Christie NHS Foundation Trust and the University of Manchester, Medical Physics and Engineering, Manchester, United Kingdom ; 7 University of Oxford, Department of Oncology, Oxford, United Kingdom ; 8 Umeå University, Department of radiation sciences, Umeå, Sweden ; 9 Odense University Hospital and University of Southern Denmark, Laboratory of Radiation Physics, Odense, Denmark ; 10 Kymenlaakso Central Hospital, Department of Medical Imaging and Radiation Therapy, Kotka, Finland ; 11 Auckland Radiation Oncology, Epsom, Auckland, New Zealand ; 12 University Medical Center Utrecht, Department of Radiotherapy, Utrecht, The Netherlands ; 13 Ghent University Hospital, Department of Radiation Oncology, Ghent, Belgium ; 14 AOU Careggi Firenze University Hospital, Department of Health Physics, Firenze, Italy ; 15 Centre Oscar Lambret, Department of Medical Physics, Lille, France ; 16 Northern Centre for Cancer Care, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom Purpose or Objective Despite growing interest in MRI, integration in external beam radiotherapy (EBRT) treatment planning uptake varies globally. In order to understand the current international landscape of MRI in EBRT a survey has been performed in 10 countries. This work reports on differences and common themes identified. Material and Methods A survey was developed covering eight topics: MRI access; MRI use; MRI to CT registration; commissioning/Quality Assurance (QA); safety; workflow/staffing; education; and future applications. The survey was distributed within 10 countries by a ‘local champion’ ensuring it reached all radiotherapy centres. Results The survey had a median response rate of 77% per country (184/442 in total). Response rates in individual countries varied between those with high response rates (≥66% in the UK/Denmark (DK)/Finland (FN)/Sweden (SE)/Netherlands (NL)/Belgium (BE)/New Zealand (NZ)) and those with response rates low enough that results cannot be considered representative of the country (≤35% in Italy (IT)/France (FR)/Australia (AU)). MRI access was varied between countries, with FR and the UK reporting the lowest rates (43% and 69% respectively). In DK/SE >80% of centres reported having dedicated MRI

Conclusion Salvage EBRT and/or HDR-VBT is effective and safe in the treatment of vaginal and pelvic relapses of endometrial cancer. It shows excellent LC, good DFS. OS appears to be related to age and distant metastasis. Second relapses are rare and can be re-treated with further VBT. Grade 4 toxicities are rare even in pre-irradiated patients. Identifying patients at higher risk for a second recurrence or distant metastases is required in order to tailor their treatment.