ESTRO 2021 Abstract Book

S1438

ESTRO 2021

Fig. 2. BIP in MRI scanner with CoBra robot

Results Tests of the BIP and robotic needle insertion in RT-MRI, showed that the BIP features could be extracted with good fidelity and the needle tip identified under T1w, T2w and DYN-B FEE sequences. sCT datasets showed a mean MAE of 59.8 HU and 65.8 HU for first and second test sites, taking on average 8.5 s to generate a complete sCT (90 slices) on our GPU (Nvidia Quadro P6000). Conclusion This report demonstrates some of the latest progress achieved from the CoBra project, as it reaches the phantom testing stage. PO-1712 Oligorecurrent nodal prostate cancer: radiotherapy QA of the randomized PEACE V-STORM phase II trial V. Achard 1 , R. Heikkilä 2 , P. Dirix 3,4 , S. Siva 5 , N. Liefhooghe 6 , A. Conde-Moreno 7 , S. Meersschout 8 , P. Muto 9 , C. Eíto 10 , M. Barrado 11 , P.M. Putora 12 , D. Zwhalen 13 , M. Scorsetti 14,15 , A. Zapatero 16 , L. Van De Voorde 17 , F. López Campos 18 , F. Couñago 19,20 , F. Vanhoutte 21 , M. Jaccard 1 , G. Dipasquale 1 , P. Ost 21 , T. Zilli 1 1 Geneva University Hospitals, Radiation oncology, Geneva, Switzerland; 2 Oslo University Hospital, Oncology, Oslo, Norway; 3 Iridium Kankernetwerk, Radiation oncology, Antwerp, Belgium; 4 University of Antwerp, Faculty of Medicine and Health Sciences, Antwerp, Belgium; 5 Epworth Healthcare and Sir Peter MacCallum , Oncology, Melbourne, Australia; 6 AZ Groeninge, Radiation oncology, Kortrijk, Belgium; 7 Hospital Universitari i Politècnic la Fe, Radiation oncology, Valencia, Spain; 8 AZ-St Jan-Brugge, Radiation oncology, Brugge, Belgium; 9 Napoli Istituto Nazionale Tumori IRCCS Fondazione Pascale, Radiation oncology, Napoli, Italy; 10 Instituto Oncólogico Clinica Universitaria IMQ, Radiation oncology, Bilbao, Spain; 11 Complejo Hospitalario de Navarra, Radiation oncology, Navarra, Spain; 12 Kantonspital St. Gallen, Radiation oncology, St. Gallen, Switzerland; 13 Kantonspital Winterthur, Radiation oncology, Winterthur, Switzerland; 14 IRCCS Humanitas Research Hospital, Radiation oncology, Rozzano (Milan), Italy; 15 Humanitas University, Biomedical Sciences, Pieve Emanuele (Milan), Italy; 16 University Hospital La Princesa, Radiation oncology, Madrid, Spain; 17 AZ St- Lucas, Radiation oncology, Ghent, Belgium; 18 Hospital Universitario Ramón y Cajal, Radiation oncology, Madrid, Spain; 19 University Hospital Quironsalud, Radiation oncology, Madrid, Spain; 20 Universidad Europea de Madrid, Medicine, Madrid, Spain; 21 Ghent University Hospital, Radiation oncology and experimental cancer research, Ghent, Belgium Purpose or Objective Optimal local treatment for nodal oligorecurrent prostate cancer (PCa) is unknown. In this setting, the ongoing prospective multicentre randomized phase II PEACE V-STORM trial is evaluating the impact of the addition of whole pelvic radiotherapy (WPRT) to metastasis-directed therapies (MDT: salvage lymph-node dissection or stereotactic body radiotherapy, SBRT) and short-term androgen deprivation therapy (ADT) on metastasis-free survival. The aim of the present study is to report the interim results of the radiation therapy quality assurance (RTQA) program. Materials and Methods Patients diagnosed with PET-detected pelvic nodal oligorecurrence (≤5 nodes) following radical local treatment for PCa, are randomized in a 1:1 ratio between arm A: MDT and 6 months of ADT, or arm B: WPRT added to MDT and 6 months of ADT. A site-specific questionnaire and a dummy run (DR) consisting of a post- prostatectomy case with two ipsilateral iliac nodal recurrences were established for both SBRT (30 Gy/3 fx) and WPRT (45 Gy/25 fx with a nodal SIB to 65 Gy) treatments. Use of IMRT or VMAT techniques was mandatory. The uploaded plans were reviewed independently by two radiation oncologists for protocol compliance of delineation and treatment planning. Case reviews were categorized as: ‘Acceptable as per protocol’ (A), ‘Acceptable Variation’ (AV), or ‘Unacceptable Variations’ (UV). UV was assigned if there could be a material impact on clinical outcomes. Results DR of 18 centers among the 26 participating centers were analyzed in this interim analysis. The overall grading for delineation review of the 1 st submitted version of the DR was rated as ′UV′ or ′AV′ for 1 and 5 centers for arm A (33%) and 3 and 6 for arm B (50%), respectively. A lower upper limit of the WPRT CTV (n=2), an inappropriate (n=1) or missing delineation (n=1) of the prostate bed, and a missing nodal target volume (n=1 for arm A and B) constituted the observed ′UV′. With a 2 nd DR version, required for 8 centers, the overall delineation review showed 2 and 5 ′AV′ for arms A and B, respectively, with no ′UV′. For the dosimetric/plan quality review, arm B showed the largest protocol agreement, with only one AV consisting of a lower boost dose to a node. The largest variability in dosimetry was observed for SBRT plans, with PTV D 90% ranging from 22.9 Gy to 32.7 Gy for node 1 (close to a bowel loop) and from 26.8Gy to 34Gy for node 2 (close to sigmoid), respectively. Six SBRT plans were rated as ′A′, while 12 as ′AV′, mainly for exceeding the dose to the bowel-