ESTRO 2020 Abstract book

S425 ESTRO 2020

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 M. Moerland 1 , A.L.H.M.W. Van Lier 1 , L.J. Van Schelven 2 , M.J. Van Son 1 , M. Peters 1 , E. Boskovic 2 , R. Schokker 1 , K.M. Van Vliet-Van Den Ende 1 , S. Van Der Vegt 1 , J. Verkerk 1 , E. Beld 1 , W.S.C. Eppinga 1 , J.J.W. Lagendijk 1 , J.R.N. Van Der Voort Van Zyp 1 1 umc Utrecht, Department Of Radiation Oncology, Utrecht, The Netherlands ; 2 umc Utrecht, DEPARTMENT Of Medical Technology & Clinical Physics, Utrecht, The Netherlands Purpose or Objective A robotic needle implant device for MR guided high dose rate (HDR) prostate brachytherapy is under development at the University Medical Center Utrecht. The purpose of this patient study is to test the feasibility and accuracy of inserting a brachytherapy needle into the prostate to a defined target point using the robotic device. Material and Methods The robot fits in a 1.5 T MR scanner and is placed between the patient’s legs. While scanning, the needle is stepwise inserted using a pneumatic tapping device to reduce prostate deformation. The needle can be shifted and angulated to have access to the prostate while avoiding the pubic bone. So far, two patients were included in this study in November and December 2019. GTV and CTV were delineated based on diagnostic MRI and PET, and a preplan was made to assess needle configuration. Before the implant, an MR scan was made in treatment position and fused with the diagnostic MR images. One of the preplanned needle positions was selected for robot insertion. The needle target point was determined on the MR image. The robot coordinates and angles were set for the target point, and the needle was tapped in while monitored with dynamic MRI. At final depth, an MR scan was made to verify the needle position and adapt the treatment plan, after which the dose was delivered. The other needles needed to complete the treatment were inserted manually using our regular clinical procedure. Accuracy of robotic needle insertion was analyzed by comparing the planned needle tip position with the realized position in MR coordinates (x=LR, y=AP, z=CC). For analysis of prostate movement due to needle insertion the translations (x, y, z direction) and rotations (around x, y, z-axis) between the MR scans before (prescan) and after needle insertion (postscan) were determined using the fusion module of the treatment planning system. Duration of the robotic procedure was recorded. Results This abstract has been withdr wn

Cancer Centre / Faculty Of Biology Medicine And Health- University Of Manchester, Division Of Cancer Sciences, Northwood / Manchester, United Kingdom ; 9 the Royal 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.