ESTRO 2020 Abstract book

S414 ESTRO 2020

hypointense region that resembled a proton dose distribution. The beam ranges measured in the MR images agreed within 2 mm with the expected values as calculated from the beam energies. The beam effects were hardly detectable at 1 nA, but clearly visible at 3 nA and higher. The series of MR images acquired post-irradiation showed a decreasing signal intensity of the beam signature, which faded with a time constant in the order of tens of seconds. The beam signatures were not observed in the highly viscose and solid materials.

Proffered Papers: Proffered papers 33.1: Image guided radiotherapy

OC-0680 Risk factors for urinary incontinence in locally advanced cervix cancer: an EMBRACE analysis S. Spampinato 1 , L.U. Fokdal 1 , R. Pötter 2 , C. Haie-Meder 3 , J.C. Lindegaard 1 , M. Schmid 2 , A. Sturdza 2 , I. Jürgenliemk- Schulz 4 , U. Mahantshetty 5 , B. Segedin 6 , P. Hoskin 7 , K. Bruheim 8 , B. Rai 9 , F. Huang 10 , R. Cooper 11 , E. Van der Steen-Banasik 12 , E. Van Limbergen 13 , R. Nout 14 , C. Kirisits 2 , K. Kirchheiner 2 , K. Tanderup 1 1 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark ; 2 Medical University/General Hospital of Vienna, Department of Radiation Oncology- Comprehensive Cancer Center, Vienna, Austria ; 3 Gustave-Roussy, Department of Radiotherapy, Villejuif, France ; 4 University Medical Centre Utrecht, Department of Radiation Oncology, Utrecht, The Netherlands ; 5 Tata Memorial Hospital, Department of Radiation Oncology, Mumbai, India ; 6 Institute of Oncology Ljubljana, Department of Radiotherapy, Ljubljana, Slovenia ; 7 Mount Vernon Hospital, Mount Vernon Cancer Centre, Northwood, United Kingdom ; 8 The Radium Hospital- Oslo University Hospital, Department of Oncology, Oslo, Norway ; 9 Postgraduate Institute of Medical Education and Research, Department of Radiotherapy and Oncology, Chandigarh, India ; 10 Cross Cancer Institute and University of Alberta, Department of Oncology, Edmonton, Canada ; 11 St James's University Hospital, Leeds Cancer Centre, Leeds, United Kingdom ; 12 Radiotherapiegroep Arnhem, Department of Radiotherapy, Arnhem, The Netherlands ; 13 UZ Leuven, Department of Radiation Oncology, Leuven, Belgium ; 14 Leiden University Medical Center, Department of Radiation Oncology, Leiden, The Netherlands Purpose or Objective To identify risk factors for urinary incontinence in Locally Advanced Cervical Cancer (LACC) patients treated with radiochemotherapy and Image-Guided Adaptive Data from the prospective, multi-institutional, observational EMBRACE I study ( An international study on MRI-guided brachytherapy in LACC ), that enrolled 1416 patients treated from 2008 to 2015, were analysed. Physician assessed (CTCAE v.3) and patient reported (EORTC) urinary incontinence was evaluated. Patient, disease and treatment related parameters were tested as risk factors in patients without bladder involvement at diagnosis. Univariate (UVA) and multivariable (MVA) analyses (Cox proportional hazards) were applied to the incidence of severe (G≥3) and moderate grade (G≥2) CTC, as well as “Very much” and “Quite a bit”+“Very much” (≥Quite a bit) EORTC answers. Persisting symptoms, defined when at least half of the follow-ups (FUP) was scored G≥1 (CTC) or ≥Quite a bit (EORTC), were also analysed (binary logistic regression). As some covariates are not independent, cross-correlation was tested with Pearson coefficient (r). In case of r>0,250, the factor with highest clinical relevance was included in MVA. Results Of 1234 patients without bladder involvement at diagnosis, 1153 and 884 patients had morbidity assessed at baseline and at least one FUP using CTC and EORTC, respectively. Median FUP was 48 (range:1-124) months, median age was 49 (21-91) years, and 31% were smokers. Mean (±SD) Brachytherapy (IGABT). Material and Methods

Conclusion This feasibility study demonstrates for the first time that the proton beam range can be accurately verified with on- line MRI in fluid-filled phantoms. Further research is mandatory to understand the mechanisms explaining the observed effects, and to assess the potential of utilizing this principle for quantitative on-line MRI-based in vivo dose verification.