ESTRO 2020 Abstract Book

S284 ESTRO 2020

potentially protect the kidneys. To provide pre-clinical data to justify a clinical trial the objectives of my project are to study: (1) the chemo-radiosensitising ability of Rucaparib TM and (2) the ameliorating effect of Rucaparib TM on cisplatin-induced kidney toxicity. If successful, this study will contribute new chemo-radiotherapeutic strategies to reduce cisplatin and (or) radiation doses in advanced stages of cervical cancer. SP-0518 Development and validation of a delta- radiomics response model for neoadjuvant radiotherapy of soft tissue sarcomas J. Peeken 1,2,3,4 , E. Chen 5 , D.S. Hippe 2 , K. Specht 6 , E. Kim 2 , N.A. Mayr 2 , M.J. Nyflot 2 , S.E. Combs 1,3,4 1 klinikum Rechts Der Isar- Technical University Of Munich, Department Of Radiation Oncology, Munich, Germany ; 2 university Of Washington, Department Of Radiation Oncology, Seattle, Usa ; 3 german Cancer Research Consortium Dktk, Partner Side Munich, Munich, Germany ; 4 helmholtz Zentrum Muenchen, Institute Off Radiation Medicine, Munich, Germany ; 5 university Of Washington, Department Of Pathology, Seattle, Usa ; 6 klinikum Rechts Der Isar- Technical University Of Munich, Department Of Pathology, Munich, Germany Abstract text Introduction: In soft tissue sarcoma (STS) patients that receive neoadjuvant radiotherapy (RT) pathological measures from the resected tumor such as the percentage of viable cells (%VC) do not have a comparable predictive power as observed in other malignant entities (Schaefer et al. IJROBP 2017). Regarding the unfavorable prognosis of high-grade STS, the selection of non-responding patients for additional therapy may help to personalize therapy regiments. The aim of this project is the development of a delta radiomics prediction model as a potential novel radiation response parameter. Material&Methods: In the course of a previous radiomics project, databases with clinical information and pre- therapeutic MRI scans were generated at the home institution at the Department of Radiation Oncology at the Technical University of Munich and at the host institution at the Department of Radiation Oncology in Seattle, USA. The scope of this work was to analyze the availability of MRI scans conducted after RT but before surgery and to prepare them for radiomic analysis. Results: Several exclusion criteria were defined including certain sarcoma histologies, treatment regiments, imaging artifacts and availability of MRI sequences. A large patient cohort with pre- and post-therapeutic imaging studies could be curated. Most patients had both MRI sequences available. Manual segmentation was successfully performed for all patients on both extracted MRI sequences. In contrast to the home institution, almost 60% of all patients received chemotherapy (CT) sequentially in addition to RT. We were able to analyze the post-CT imaging studies, too. The %VC could be determined for the majority of patients. For the remaining patients, the parameter is currently analyzed retrospectively by pathologists at both institutions. First radiomic analyses have been undertaken for quality assurance purposes. Radiomics feature analyses and model building will be performed in the upcoming months. Special emphasis will be laid on the differential influence of CT and RT. Discussion: The upcoming results will show if radiomic features can be used as a basis for response prediction in STS patients. However, the prospective models will need to compete with the pathological measure “%VC which is

currently used as an endpoint in multiple prospective trials.

SP-0519 Evaluation of Motion Mitigation for Abdominal Radiotherapy M. Daly 1 1 University College London Hospitals NHS Trust, Radiotherapy, London, United Kingdom Abstract text Background: Abdominal organ motion must be taking into consideration for delivery of accurate radiotherapy to organs such as the pancreas and biliary tract. There are ways to reduce this, such as the use of an abdominal compression belt or arch to limit respiratory motion, as well as respiratory-correlated 4D scans to quantify motion. Our department does not currently offer abdominal compression, or abdominal SBRT. Methods & materials: A one-week radiation therapy observership was completed at Princess Margaret Hospital in Toronto, Canada during September 2019. The expected areas to be studied included observation of: SBRT treatment delivery for abdominal cancers, SBRT planning methods for abdominal tumours, and respiratory- correlated (4D) CT acquisition. Abdominal compression and other motion mitigation strategies (such as breath hold with Elekta ABC) were also to be observed. The feasibility of implementing similar practices in our home department was to be assessed. Results: Aspects of various parts of the patient pathway were observed. Scanning and planning techniques were observed. The use of both abdominal compression and ABC were observed on the treatment units. At least three patients were observed on treatment for SBRT to the liver. Discussions with specialist radiation therapists (research and education) occurred regarding the host institution's approach to research and staff education. Motion mitigation strategies were selected on a patient-by- patient basis, based on the reduction of motion in that particular case. Conclusion: Implementation of abdominal compression and SBRT is feasible within our home department based on what was learned on this observership. Effective staff education is vital when implementing complex abdominal motion mitigation techniques, regular staff update sessions are a useful way of keeping skills current. Patient education regarding motion management techniques, as well as selecting strategies on a case-by-case basis improve patient compliance. SP-0520 Prevetion of the radio-induced pulmonary fibrosis by Muse cells H. Dushime 1 , B. Petit 2 , J. Ollivier 2 , N. Gault 1 , M. Vozenin 2 , P. Romeo 1 1 cea, Drf/Jacob/Ircm/Lrts, Fontenay-Aux-Roses Cedex, France ; 2 chuv, Oncologie, Lausanne, Switzerland Abstract text Despite improved radiotherapy delivery conditions, radiation induced pulmonary fibrosis (RIPF) is a common complication in patients with lung or breast cancer after receiving thoracic radiotherapy. Radiation-induced injury in healthy tissues remain the limiting factor for dose escalation and tumor control. The average incidence of RIPF is 16-28% after radiotherapy(Cella et al. 2014). RIPF is characterized by progressive destruction of lung tissue and gas exchange disruption. To date no medical therapy has been approved for clinical use. Muse cells ("Multilineage differentiating stress enduring"