ESTRO 2022 - Abstract Book

S534

Abstract book

ESTRO 2022

1 EORTC, RTQA, Brussels, Belgium; 2 Institut Bergonie, Department of Radiotherapy, Bordeaux, France; 3 Institut Gustave Roussy, University of Paris Saclay, Department of Radiation Oncology, Villejuif, France; 4 Institut de Cancérologie de l'Ouest - site René Gauducheau, Department of Radiation Oncology, Nantes, France; 5 Centre Azuréen de Cancérologie, Department of Radiation Oncology, Mougins, France; 6 Centre Léon Bérard, Department of Radiation Oncology, Lyon, France; 7 Croix rouge française, centre saint louis, Department of Radiation Oncology, Toulon, France; 8 Centre François Baclesse, Department of Radiation Oncology, Caen, France; 9 CHU Jean-Minjoz, Department of Radiation Oncology, Besançon, France; 10 CFRO-Clinique Pasteur, Department of Radiation Oncology, Brest , France; 11 Institut Claudius Regaud/ Institut Universitaire du Cancer de Toulouse - Oncopole, Department of Radiation Oncology, Toulouse, France; 12 Centre Eugène Marquis, Department of Radiation Oncology, Rennes , France; 13 Ipswich Hospital, Department of Oncology, Ipswich, Suffolk, United Kingdom; 14 Hospital Clinic de Barcelona, Radiation Oncology Department, Barcelona, Spain; 15 Institut Claudius Regaud-Institut Universitaire du Cancer de Toulouse, , Department of Medical Physics, Toulouse, France; 16 Universitair Ziekenhuis Leuven, Department of Radiation Oncology, Leuven, Belgium; 17 Geneva University Hospital, Department of Radiation Oncology, Geneva, Swaziland ; 18 UNICANCER, UNICANCER, Caen, France; 19 Institut Gustave Roussy, Department of Radiation Oncology, Villejuif, France; 20 Institut Gustave Roussy, University of Paris Saclay, Department of Cancer Medicine, Villejuif, France; 21 University Hospital Zurich, University of Zurich, Department of Radiation Oncology, Zurich, Switzerland Purpose or Objective The PEACE-1 trial, sponsored by Unicancer, is a prospective randomized phase 3 study on androgen deprivation therapy (+/- docetaxel) with/without local radiotherapy and with/without abiraterone acetate and prednisone in men with metastatic hormone-naïve prostate cancer (n=1173). Retrospective individual case review (ICR) is an integral part of the radiotherapy quality assurance (RTQA) process in the trial and was provided by RTQA group at the EORTC. This study describes the interim results of ICR for patients accrued in the two radiotherapy arms and assesses the compliance level to the study protocol. Materials and Methods A total of 59 out of 81 participating institutions have sent their cases anonymized for the extensive central review, 11% of which had their radiotherapy delivered using 3DCRT. Each uploaded DICOM RT plan were reviewed by a radiation oncologist and a medical physicist for protocol compliance of target volume and organs at risks (OARs) delineation, as well as dose specifications. The outcome of the case reviews were classified as acceptable ”A”, acceptable variation “AV”, or unacceptable variation “UV”. Results The trial closed for accrual in December 2018. A total of 584 patients were recruited in the radiotherapy arms and 533 complete RT plans were uploaded to the EORTC. To date, 485 (91%) have been reviewed and analyzed. For the delineation review, 64 (13%) cases were unacceptable; specifically, 43 instances of erroneous CTV delineation, 21 instances of erroneous PTV delineation, and 19 instances of missing or improperly delineated OARs were observed. After excluding the unacceptable delineated cases, 421 cases were reviewed for dose and plan: 401 (95%) of them were either A or AV. Only 19 cases were assigned UV, mainly for insufficient PTV coverage. In 6 cases, dose constraints to OARs were reasons for unacceptable review. Table-1: Dosimetric results of the interim ICR for OARs OARs Protocol dose constraints Mean observed values (range, SD) Rectum V60 ≤ 50% 16.7% (0 – 50%, 8%) V70 ≤ 25% 7.8% (0 – 27.6%, 5%) V74 ≤ 5% 0.8% (0 – 10.7%, 1%) Bladder V60 ≤ 50% 14% (0 – 96%, 11%) V70 ≤ 25% 0.8% (0 – 85%, 8%) Femoral heads V50 ≤ 10% 1% (0 - 65%, 5%)

Conclusion RTQA is a critical component in radiotherapy trials. It is reassuring that 82% of the overall review was considered acceptable in PEACE-1. Of the limited number of unacceptable cases, most were due to CTV delineation or PTV coverage issues, while OARs were significantly less affected.

OC-0610 Characteristics of modern EBRT and its association with second primary cancer incidence

M. Jahreiß 1 , K. Aben 2 , M. Hoogeman 1 , M. Dirkx 1 , F. Pos 3 , T. Janssen 4 , A. Dekker 5 , B. Vanneste 5 , A. Minken 6 , C. Hoekstra 6 , R.J. Smeenk 7 , L. Incrocci 1 , W. Heemsbergen 1 1 Erasmus MC Cancer Institute, Radiotherapy, Rotterdam, The Netherlands; 2 Netherlands Comprehensive Cancer Institue, Research, Utrecht, The Netherlands; 3 The Netherlands Cancer Institute , Radiation Oncology, Amsterdam, The Netherlands; 4 The Netherlands Cancer Institute, Radiation Oncology, Amsterdam, The Netherlands; 5 GROW Institute for Oncology and Developmental Biology, Radiation Oncology (Maastro), Maastricht, The Netherlands; 6 Radiotherapiegroep , Radiation Oncology, Deventer, The Netherlands; 7 Radboud University Medical Center, Radiation Oncology, Nijmegen, The Netherlands