ESTRO 37 Abstract book

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ESTRO 37

Purpose or Objective Intrafraction motion is of special interest in modern radiotherapy. Patients receiving radiotherapy for head and neck cancer (HNC) or central nervous system (CNS) tumours are typically immobilized with closed thermoplastic masks which cover the face to avoid any unwanted movements. In this prospective study we evaluated the intrafraction motion in patients with simple thermoplastic masks. We applied continuous surface imaging using visible light which offers the possibility to monitor patients’ movements in 3D-space without any additional radiation exposure. Material and Methods We observed twenty-three patients during 399 fractions that underwent radiotherapy or radiochemotherapy for HNC (adjuvant/definitive) or CNS – tumours (primary or secondary, excluding stereotactic indications). During each treatment session the motion of the patient was continuously measured using the Catalyst TM optical surface scanner (C-RAD AB, Sweden) and compared to a reference scan taken at the beginning of each session. The Catalyst TM system works through an optical surface scanning with LED light (blue: λ = 450 nm) and reprojection captured by a CCD camera (green: λ = 528 nm; red: λ = 624 nm), which provide target position control during treatment delivery. For 3D surface reconstruction, the system uses a non-rigid body algorithm to calculate the distance between the surface and the isocenter and using the principle of optical triangulation. Three-dimensional deviations and relative position differences during the whole treatment fraction were calculated by the system and analyzed statistically. Results Overall, the maximum magnitude of the deviation vector showed a mean for all patients of 1.03 mm ± 0.61 mm (standard deviation) (95%-CI: [0.34 – 2.54] mm) and a median of 0.85 mm during dose application (beam-on time only). Along the longitudinal and vertical axis changes were quite similar (-0.14 mm ± 0.8 mm vs. -0.19 mm ± 0.67 mm), on the lateral axis the mean change was 0.41 mm ± 0.73 mm. 99% of the whole beam-on time the magnitude of the deviation vector was under 1.68 mm. The mean net beam-on time of radiation therapy was 219 ± 77 seconds. According to Friedman’s test, differences in the distributions between the three possible directions (lateral, longitudinal and vertical) were significant (p<0.01). In Post-Hoc-analysis a dissimilarity between the lateral and longitudinal axis, as well as the lateral and vertical direction could be verified (p<0.01); whereas there was no dissimilarity between the longitudinal and vertical axis (p=1.0). A weak correlation between the fraction time and the magnitude of deviation could be verified (Kendall Tau=0.24; p<0.01). Conclusion Real-time intrafraction motion in 399 CNS and head and neck cancer radiotherapy fractions was less than three millimeters in all directions. Based on these results any movements stay within clinically used PTV - setup margins in a non-stereotactic environment. EP-1223 Validating RTOG RPA Classes of brain metastases in patients treated with whole brain radiation N. Vijayaraghavan 1 , T. Elumalai 1 , S. Soman 1 , S.H. Kombathula 1 , P. Vedasoundaram 1 , J. Pandjatcharam 1 1 JIPMER, Radiation Oncology, Puducherry, India Purpose or Objective The objective of the study is to validate the prognostic tool, RTOG Recursive Partitioning Analysis (RPA) classes in our patients with brain metastases treated with whole brain radiation Material and Methods

are very promising, with a local control of 100% and non patient with facial nerve compromise. EP-1221 Hypoxia imaging with 18F-FAZA PET/CT in Radiotherapy Planning for High Grade Gliomas F. Zerbetto 1 , V. Bettinardi 2 , A. Deli 1 , A. Fodor 1 , P. Mapelli 2 , E. Incerti 2 , F. Fallanca 2 , C. Deantoni 1 , M. Pasetti 1 , I. Dell'Oca 1 , A. Chiara 1 , N. Slim 1 , G. Rossi 1 , C. Gumina 1 , M. Picchio 2 , A. Bolognesi 1 , L. Gianolli 2 , N. Di Muzio 1 1 San Raffaele Scientific Institute, Department of Radiation Oncology, Milan, Italy 2 San Raffaele Scientific Institute, Nuclear Medicine Department, Milan, Italy Purpose or Objective Hypoxia plays a central role in high grade Gliomas development, angiogenesis, growth and resistance to radio and chemotherapy. In hypoxic conditions the expression of transcriptional factors, such as the hypoxia- inducible factor (HIF), is involved in tumor malignant progression, decreasing patient survival.In this study we evaluated how the information about tumor oxygenation status, obtained from18F-FAZA PET/TC, could modify our treatment planning. Material and Methods From April 2016 to May 2017, 12 patients with diagnosis of high grade glioma, underwent a baseline 18F-FAZA- PET/TC in order to define maximum standardized uptake value (SUVmax) and to generate 7 different biological Volumes of Interest (VOIs). The first VOI was manually drawn by an experienced Nuclear Medicine Physician who included the whole uptake area (BTV-1). Starting from BTV-1 three other volumes have been automatically generated as 40%, 50% and 60% of the SUVmax (BTV-40, BTV-50 and BTV60). Further, 3 BTVs have been generated as representative of the Hypoxia regions based on the tissue-to-muscle ratio, respectively with thresholds of 1.2, 1.3 and 1.4. Target delineation was performed using contrast enhanced T1 + T2/FLAIR Magnetic Resonance (MR) sequences, with Dynamic Susceptibility Contrast and Dynamic Contrast Enhanced perfusion, fused with the planning CT. Gross Tumor Volume (GTV) included tumor postcontrast T1 weighted images, without peritumoral edema, according to the European Organization for Research and Treatment of Cancer (EORTC), plus regions of abnormal T2/FLAIR MR in case of low grade glioma concomitant areas. Clinical Target Volume (CTV) was generated adding 20 mm to GTV, and Planning Target Volume (PTV) was obtained adding an isotropic margin of 5 mm to CTV. After the contouring, planning MR was matched with FAZA PET/TC imaging. Results In every patients, the T1 MR enhanced volume, corresponding to GTV high grade component, included the 7 FAZA-VOIs, validating the hypothesis that hypoxia is strictly correlated with the tumor aggressiveness. Conclusion In our experience the biological information from 18F- FAZA PET/CT doesn’t modify the target delineation but it could be used for dose painting with dose escalation on the hypoxic areas. EP-1222 Intrafraction motion in CNS and HNC radiotherapy: 399 fractions using an optical surface scanner D. Reitz 1 , G. Carl 1 , S. Schönecker 1 , P. Freislederer 1 , M. Pazos 1 , M. Reiner 1 , M. Niyazi 1 , U. Ganswindt 1 , C. Belka 1 , S. Corradini 1 1 Department of Radiation Oncology- University Hospital- LMU Munich, Radiation Oncology, Munich, Germany