ESTRO 38 Abstract book

S421 ESTRO 38

Conclusion Tumor persistence and distant recurrence were the main patterns of lack of disease control. Persistence after (chemo)radiotherapy negatively impacted survival. Out- of-field was the least frequent recurrence pattern. It is acceptable to maintain IFI technique. PO-0809 Gross Tumor Volume delineation in pancreatic cancer using MRI: final results of a multicenter study. L. Caravatta 1 , F. Cellini 2 , N. Simoni 3 , C. Rosa 1 , R.M. Niespolo 4 , M. Lupattelli 5 , V. Picardi 6 , G. Macchia 6 , A. Sainato 7 , G. Mantello 8 , F. Dionisi 9 , M.E. Rosetto 10 , V. Fusco 11 , F. Navarria 12 , A. De Paoli 12 , A. Guido 13 , C. Vecchi 14 , R. Basilico 15 , R. Cianci 16 , A. Delli Pizzi 17 , M. Di Nicola 18 , G.C. Mattiucci 2 , V. Valentini 2 , A.G. Morganti 13 , D. Genovesi 1 1 “SS Annunziata” Hospital- “G. D’Annunzio” University, Radiation Oncology Unit, Chieti, Italy ; 2 Gemelli Advanced Radiation Therapy Center- Fondazione Policlinico Universitario "A. Gemelli"- Catholic University of Sacred Heart, Radiotherapy Unit, Rome, Italy ; 3 Azienda Ospedaliera Universitaria, Radiotherapy Unit, Verona, Italy ; 4 Azienda Ospedaliera S. Gerardo, Department of Radiation Oncology, Monza, Italy ; 5 University of Perugia and Perugia General Hospital, Radiation Oncology Section, Perugia, Italy ; 6 "Giovanni Paolo II" Foundation- Catholic University of Sacred Heart, Radiotherapy Unit- Department of Oncology, Campobasso, Italy ; 7 Azienda Ospedaliera Universitaria Pisana, Radiotherapy Unit, Pisa, Italy ; 8 State Hospital, Department of Radiotherapy, Ancona, Italy ; 9 Azienda Provinciale per i Servizi Sanitari- APSS-, Proton Therapy Unit- Department of Oncology, Trento, Italy ; 10 Ospedale Belcolle, Department of Radiation Oncology, Viterbo, Italy ; 11 Centro di Riferimento Oncologico Regionale, Department of Radiation Oncology, Rionero in Vulture- Potenza, Italy ; 12 Centro di Riferimento Oncologico- National Cancer Institute, Department of Radiation Oncology, Aviano, Italy ; 13 University of Bologna- S. Orsola-Malpighi Hospital, Radiation Oncology Center- Department of Experimental- Diagnostic and Specialty Medicine - DIMES, Bologna, Italy ; 14 Tecnologie Avanzate, Srl, Torino, Italy ; 15 "SS Annunziata” Hospital- “G. D’Annunzio” University, Department of Radiology, Chieti, Italy ; 16 “SS Annunziata” Hospital- “G. D’Annunzio” University, Department of Radiology-, Chieti, Italy ; 17 “SS Annunziata” Hospital- “G. D’Annunzio” University, Department of Radiology, Chieti, Italy ; 18 “G. D’Annunzio” University, Laboratory of Biostatistics- Department of Medical- Oral and Biotechnological Sciences, Chieti, Italy Purpose or Objective Variations in volumes delineation in pancreatic cancer have been reported in previous studies. Thanks to the high soft tissue resolution, Magnetic Resonance Imaging (MRI) could improve the accuracy of tumor delineation in pancreatic cancer compared to Computed Tomography (CT). Since recommendations for pancreatic cancer contouring using MRI have been recently provided, a multi- institutional contouring dummy-run study was proposed to evaluate the impact of MRI on inter-observer agreement in Gross Tumor Volume (GTV) . Material and Methods The study group for gastrointestinal cancers of the Italian Association of Radiation Oncologists (AIRO) proposed a multicenter contouring study to the centers interested in pancreatic cancer treatment. Two clinical cases of borderline resectable (Case 1) and locally advanced unresectable (Case 2) pancreatic cancer were selected by two radiologists and two radiation oncologists expert in pancreatic cancer. In two sequential steps, diagnostic contrast-enhanced CT scan and 1.5T MRI sequences were