ESTRO 2020 Abstract Book

S388 ESTRO 2020

Marsden Nhs Foundation Trust / The Institute Of Cancer Research, Radiotherapy, London, United Kingdom ; 10 gustave Roussy Institute, Department Of Radiation Oncology, Villejuif, France ; 11 royal Liverpool University Hospital, Urology, Liverpool, United Kingdom ; 12 hartmann Radiotherapy Center / Rafael Institute- Center For Predictive Medicine, Department Of Radiotherapy, Levallois-Perret, France ; 13 antoine Lacassagne Cancer Center / University Of Côte D'azur, Department Of Radiation Oncology, Nice, France ; 14 institut Oncològic Teknon- Quironsalud, Radiotherapy, Barcelona, Spain ; 15 genesis Health Care Partners- Inc, Department Of Radiation Oncology, San Diego- California, Usa ; 16 humanitas Clinical And Research Hospital / Humanitas University, Department Of Radiotherapy And Radiosurgery / Department Of Biomedical Sciences, Rozzano- Milan, Italy ; 17 s. Gerardo Hospital- University Of Milan Bicocca, Department Of Radiation Oncology, Milan, Italy ; 18 university Of Florence, Radiotherapy Department, Florence, Italy ; 19 henry-S.-Kaplan Cancer Center- Chru De Tours, Oncology-Radiotherapy Department, Tours, France ; 20 centre O. Lambret, Academic Department Of Radiation Oncology, Lille, France Purpose or Objective Up to 52% of patients treated with definitive radiotherapy (RT) for prostate cancer (PCa) are at risk of intraprostatic recurrence during their life [1]. Re-irradiation with stereotatic body RT (SBRT) is emerging as a feasible and safe therapeutic alternative in patients with local recurrence. So far, no consensus or guidelines exist on this topic. The purpose of this project, under the approval of the ESTRO ACROP Committee, is to investigate the expert opinion on salvage SBRT for intraprostatic relapse after RT. Material and Methods The structure of this study follows a previously Delphi consensus published by Kaljouw et al. on salvage PCa brachytherapy, conducted by the Uro-GEC working group of the Groupe Euopéen de Curiethérapie – European Society for Radiotherapy and Oncology (GEC-ESTRO). [2]. A reviewing committee, that is a panel of leading radiation oncologists plus an urologist, expert in PCa management, structured and approved a final version of a questionnaire on the topic. Three rounds of questionnaires have been sent to experts on PCa reirradiation, and after each round was completed, the responses and the relevant comments were sent back anonymously to the participants. A percentage of 80% agreement has been established as the threshold for reaching the consensus. Results Eighteen experts agreed to participate in the study. Up today, 2 out of 3 rounds have been completed by all participants. After the first round, consensus was reached on 7 out of the 40 questions (18% of the questions). Specifically, consensus was achieved in 21% (4/19), 28% (2/7) and 7% (1/14) questions of first, second and third section of the questionnaire, respectively. In the second round consensus increased and was reached on 4 additional questions, raising the consensus percentage to 28%. As far as the rectum is concerned, opinions were divided, with a slight prevalence (55.6%) of those who recommended a dose between 95 and 105 Gy. Analogously, agreement was not found for the bladder, with 44.4% of participant suggesting a dose between 85 and 95 Gy and the same proportion advising higher doses, between 95 and 105 Gy. Regarding biopsies, only 22.2% of participants agree that they are always needed for diagnosis of recurrence. Moreover, only 16.7% of participants advocated the use of

ultrasound (US) for guiding biopsies. 72.2% and 83.3% of participants shared the opinion that between 12 and 18 US-guided biopsies should be taken at time of recurrence for whole and partial gland treatment, respectively. The main areas where disagreement persists are patients’ selection, imaging necessary for diagnosis and dosimetric issues concerning both the CTV and the OARs. Conclusion After the third and final round is concluded, the results of the survey will be analyzed and the consensus derived from the panel of experts will be spread by dissemination activities. We expect to provide useful information to aid in decision-making for salvage SBRT and provide knowledge gaps for future research. OC-0695 MRI-guided robotic needle insertion for prostate brachytherapy: proof of principle study in patients OC-0696 Development of dose constraints to the brain areas implied in cognition: a prospective study J. Jacob 1 , M. Ribeiro 2 , M.A. Benadjaoud 3 , C. Jenny 4 , L. Feuvret 1 , J. Simon 1 , M. Bernier 5 , D. Antoni 6 , K. Hoang- Xuan 2 , D. Psimaras 2 , A. Carpentier 7 , D. Ricard 8 , P. Maingon 1 1 groupe Hospitalier Pitié-Salpêtrière-Charles Foix, Department Of Radiation Oncology, Paris, France ; 2 groupe Hospitalier Pitié-Salpêtrière-Charles Foix, Department Of Neurology 2, Paris, France ; 3 institut De Radioprotection Et De Sûreté Nucléaire, Radiobiology And Regenerative Medicine Research Service- Direction Of Human Health, Fontenay-Aux-Roses, France ; 4 groupe Hospitalier Pitié-Salpêtrière-Charles Foix, Department Of Medical Physics, Paris, France ; 5 institut De Radioprotection Et De Sûreté Nucléaire, Laboratory Of Epidemiology, Fontenay-Aux-Roses, France ; 6 centre Paul Strauss, Department Of Radiotherapy, Strasbourg, France ; 7 groupe Hospitalier Pitié-Salpêtrière-Charles Foix, Department Of Neurosurgery, Paris, France ; 8 hôpital D'instruction Des Armées Percy, Department Of Neurology, Clamart, France Purpose or Objective This prospective work aims at elaborating dose constraints to the brain areas implied in cognitive functions using the dosimetric data and results of the neuropsychological assessments performed in high-grade glioma (HGG) patients. A new concept of dose constraints would be introduced for intensity-modulated radiotherapy in brain tumours. Material and Methods A bicentric study has been recruiting 174 patients treated with concurrent chemoradiotherapy for supratentorial HGG since 2015 (ClinicalTrials.gov identifier: NCT02544178). Focal brain radiotherapy was performed following surgical biopsy or excision. Temozolomide was administered daily concurrently with radiotherapy. Delineation of the brain areas implied in cognitive functions, e.g. both hippocampi, subventricular zones, the corpus callosum, the frontal and temporal lobes, the normal brain, i.e. the brain minus the Planning Target Volume (PTV), was performed for each patient using computed tomography and magnetic resonance imaging. Dose prescription was 60 Gy in 30 daily fractions to the PTV. Neuropsychological assessments were performed at baseline, i.e. after surgery and before chemoradiotherapy, then annually by specialised teams. Logistic functional Abstract withdrawn