ESTRO 2020 Abstract book

S254 ESTRO 2020

significantly correlated with dyspnea. Dose volume metrics in the range of 5-20 Gy were significantly correlated with dyspnea. At the MV, a three variable model including COPD, heart volume and the relative lungs volume receiving more than 10 Gy (V 10Gy ) was selected. The model displays a good performance given by ROC-AUC= 0.74 [95%CI 0.64-0.88] and Rs= 0.376. Conclusion In the analyzed cohort of NSCLC patients treated with SBRT, 24% of patients developed dyspnea of grade ≥2 within 6 months after RT. Patients comorbidity (COPD) and individual patient characteristic (heart volume) along with V 10Gy resulted to be independent prognostic factors for dyspnea of any grade after lung SBRT. Further modelling efforts are needed for RILD prediction in hypofractionated treatments in order to identify patients at high risk for developing lung toxicity more accurately. [1] G. Defraene et al. Radiother and Oncol, 2019 [2] G. Nalbantov et al. Radiother and Oncol, 2013 PD-0431 Multicentre clinical radiotherapy audit in rectal cancer: results of the IROCA project M. Fundowicz 1 , A. Aguiar 2 , C. Lopes de Castro 2 , M.G. Torras 3 , L. Deantonio 4 , E. Konstanty 5 , M. Kruszyna Mochalska 5 , M. Macia 6 , E. Canals 7 , M. Caro 8 , C. Pisani 4 , D. Zwierzchowska 9 , J. Molero 8 , A. Eraso 6 , J. Lencart 10 , C. Muñoz-Montplet 11 , L. Carvalho 2 , M. Krengli 4 , J. Malicki 12 , F. Guedea 6 1 Greater Poland Cancer Centre, Department of Radiation Oncology, Poznan, Poland ; 2 Instituto Portugues de Oncologia, Radiotherapy Department, Porto, Portugal ; 3 Institut Català d’Oncologia- L'Hospitalet, Clinical management, Barcelona, Spain ; 4 Università degli Studi del Piemonte Orientale UNIUPO, Radiotherapy Department, Novara, Italy ; 5 Greater Poland Cancer Centre, Physics Department, Poznan, Poland ; 6 Institut d’Oncologia- L'Hospitalet, Radiotherapy Department, Girona, Spain ; 8 Institut Català d’Oncologia- L'Hospitalet, Radiotherapy Department, Badalona, Spain ; 9 Greater Poland Cancer Centre, Department of Trainings and Scientific Cooperation, Poznan, Poland ; 10 Instituto Portugues de Oncologia, Physics Department, Porto, Portugal ; 11 Institut Català d’Oncologia- L'Hospitalet, Physics Department, Barcelona, Spain ; 12 Dept of Electroradiology- University of Medical Sciences, Department of Radiation Oncology, Poznan, Poland Purpose or Objective Despite the widely- recognized value of clinical audits, relatively few have been performed in the field of radiation oncology. The IROCA project—Improving Quality in Radiation Oncology through Clinical Audits—is a multicentre collaboration among six European comprehensive cancer centres to conduct clinical audits to assess adherence to radiotherapy protocols for the Multi-institutional retrospective cohort study of 221 randomly-selected patients who underwent radiotherapy for rectal cancer in 2015. Participants were randomly selected from institutional databases. Numerous clinical indicators were assessed, including: 1) distance from the treatment of cancer. Material and Methods Poster discussion: PH: Implementation of new techniques 1 Català d’Oncologia- L'Hospitalet, Radiotherapy Department, Barcelona, Spain ; 7 Institut Català

tumour to the mesorectal fascia; 2) presentation of cases to a multidisciplinary tumour board (MTB) or departmental clinical session (DCS); 3) suitability and adherence to the prescribed treatment (dose, fractionation, and duration); 4) number of imaging verifications performed; 5) postoperative circumferential resection margin; 6) appropriateness of clinical follow-up; and 7) registration of adverse effects. Results The audits were conducted in 2017. Pretreatment MRI was performed in 87.3% of patients (range, 61.5%-100%) and thoracoabdominal computed tomography (CT) in 81.9% of cases (range, 15.0%-100%). Overall, 63.8% (range, 0%- 100%) and 75.6% (50%-95.0%) were presented to the DCS and MTB, respectively. The mean interval between biopsy and first visit to the radiotherapy department was 37.6 days (range, 21.6 - 58.6), with a mean of 22 days (15.1 - 38.8) between the first visit and initiation of radiotherapy. Treatment interruptions ≥ one day were observed in 43.9% (2.5%-90%) of cases. Radiotherapy treatment was completed within the prescribed time in 55.7% of cases. Conclusion This multi-institutional clinical audit shows considerable variability in clinical practice among the participating centres. Although the clinical indicators showed good adherence to good clinical practice overall, the audit revealed several areas that could be targeted for improvement. This study demonstrates the benefits of conducting clinical audits in radiotherapy, suggesting a need to promote the wider use of routine clinical audits in radiation oncology. PD-0432 Implantable Sensors for Quantifying Tumor Oxygenation G. Ekchian 1 , J. Tokuda 2 , J. Freedman 1 , H. Harens 1 , R. Cormack 3 , L. Lee 3 , M. Cima 4 1 Massachusetts Institute of Technology, Koch Institute for Integrative Cancer Research, Cambridge, USA ; 2 Brigham and Women's Hospital, Radiology, Boston, USA ; 3 Brigham and Women's Hospital, Radiation Oncology, Boston, USA ; 4 Massachusetts Institute of Technology, Materials Science and Engineering, Cambridge, USA Purpose or Objective The need for clinical oxygen sensing is widespread and is particularly acute in oncology where clinical data has shown that patients with hypoxic tumors fare worse, including higher relapse rates and lower overall survival. Past and current methods of oxygen sensing have generally required an invasive step for each measurement or are qualitative and indirect. This has prevented hypoxia- targeting therapies, like radiation dose escalation, from being implemented clinically. Silicones, which have been shown to be safe in vivo for other applications, have quantitative MR properties that correlate to oxygen levels in pre-clinical animal models. 1,2 The suitability of silicones for in vivo oxygen sensing applications is strongly dependent on formulation and materials design. We report on the translation of this material family to a clinical (e.g. clinical MRI scanner) setting and present options for implementation of this sensor. Our work has also led to a pilot human trial evaluating this material in cervical cancer. Material and Methods Oxygen sensitive silicones are produced by mixing pre- cured elastomer and silicone oil. Homogeneous mixtures were heat cured to allow for crosslinking of the elastomer. Silicone oil/elastomer combinations, elastomer, and neat silicone oils were measured using an inversion recovery This abstract will be released at a later date