ESTRO 36 Abstract Book

S674 ESTRO 36 _______________________________________________________________________________________________

4 University Hospital Freiburg, Department of Nuclear Medicine, Freiburg, Germany 5 University Hospital Halle-Wittenberg, Department of Radiation Oncology, Halle-Wittenberg, Germany 6 University Hospital Dresden, Department of Radiation Oncology, Dresden, Germany 7 University Klinik Rechts der Isar- TU Munich, Department of Radiation Oncology, Munich, Germany 8 General Hospital Vienna- Medical University Vienna, Department of Radiation Oncology, Vienna, Austria 9 University Hospital of Cologne, Department of Radiation Oncology, Cologne, Germany 10 University Hospital Mainz, Department of Radiation Oncology, Mainz, Germany 11 University Hospital Frankfurt, Department of Radiation Oncology, Frankfurt, Germany 12 University Hospital Freiburg, Department of Radiology, Freiburg, Germany 13 University Hospital Heidelberg, Department of Radiation Oncology, Heidelberg, Germany 14 German Cancer Consortium DKTK, Partner Site Freiburg, Freiburg, Germany Purpose or Objective To evaluate the inter-observer variability in the gross tumor delineation of hepatocellular carcinoma (HCC) in a multicenter panel. Material and Methods The analysis was performed within the working group on Stereotactic Radiotherapy of the German Society for Radiation Oncology (DEGRO). A total of 9 German, Austrian and Swiss centers with experience in upper abdominal stereotactic body radiotherapy (SBRT) participated in the study. Sixteen physicians (12 radiation oncologists, 2 liver surgeons, 1 radiologist and 1 nuclear medicine physician) were invited to delineate the gross tumor volume (GTV) of three anonymized HCC cases. A multiphasic CT scan from each patient was distributed to the panel before the annual meeting. In the first case participants were asked to delineate a peripheral well defined HCC. The second case included a patient with a multifocal HCC (1 conglomerate and 1 peripheral tumor). This patient was previously treated with transarterial chemoembolization (TACE) and the peripheral lesion was adjacent to the previous TACE site (lipiodol uptake site). In the last case the participants were given a CT with an extensive HCC involvement with a portal vein thrombosis and inhomogeneous liver parenchyma due to extensive cirrhosis. The inter-observer agreement (IOA) was evaluated according to Landis and Koch. Results The IOA for the first case was excellent (kappa: 0.85) and for the second case moderate (kappa 0.48) for the peripheral tumor and substantial (kappa 0.73) for the conglomerate. In the case of the peripheral tumor the inconsistency is most likely explained due to the necrotic tumor cavity after TACE caudal to the viable tumor. In the last case the IOA was fair with a kappa of 0.34 with a significant heterogeneity concerning the borders of the tumor and the extent of the portal vein thrombosis (PVT). We did not find significant differences between the different subgroups of experts except for the last case were the physicians who were involved in the diagnosis (radiologists and nuclear medicine physician) showed a better IOA (kappa: 0.64) Conclusion The IOA was very good among the cases were the tumor was well defined. Yet, in complex cases were the tumor did not show the typical characteristics or in cases with lipiodol deposits inter-observer agreement was compromised.

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EP-1252 Update of Stereotactic body radiation therapy for pancreatic adenocarcinoma: efficacy and safety X. Chen 1 , E. Sanchez 1 , A. Montero 1 , O. Hernando 2 , M. Lopez 1 , J. Garcia 3 , J.M. Perez 4 , R. Ciervide 1 , J. Valero 1 , M. Garcia-Aranda 1 , R. Alonso 2 , D. Zucca 3 , M.A. De la Casa 3 , B. Alvarez 1 , J. Marti 3 , L. Alonso 4 , P. Fernandez- Leton 3 , C. Rubio 1 1 Hospital Universitario HM Sanchinarro, Radiation Oncology, Madrid, Spain 2 Hospital Universitario HM Puerta del Sur, Radiation Oncology, Madrid, Spain 3 Hospital Universitario HM Sanchinarro, Medical Physics, Madrid, Spain 4 Hospital Universitario HM Puerta del Sur, Medical Physics, Madrid, Spain Purpose or Objective To review feasibility and single center experience with stereotactic body radiation therapy (SBRT) in pancreatic adenocarcinoma. Material and Methods Since February 2014, 15 (p) patients with a median age of 69.8 years (range 53-86) with histologically proven adenocarcinoma of the pancreas were enrolled on this protocol. Six p (40%) were treated with a radical intent, 5 p (33%) as a part of a neoadjuvant treatment and 4 p (27%) under a palliative intention. Prior to radiation, at least 2 gold fiducials markers were located into the tumor guided by endoscopic ultrasound. All the SBRT treatments included CT or PET-CT for GTV delineation, treatment technique was intensity-modulated radiation therapy (IMRT) and daily image-guided radiation therapy (IGRT) with intrafraction control of tumor motion with a Novalis Exactrac Adaptive Gating System. Total dose: 50 Gy in 10 fractions were prescribed in 13 p (87%), 1 p was treated with 35 Gy in 5 fractions and 1 p was treated with 40Gy in 10 fractions. Results With a median follow-up of 8 months (range 3 - 24 months), 2 p (13%) are alive without tumor, 4 p (26%) are alive with tumor and 9 p (61%) have died; median overall survival (OS) was 13.4 months (range 8.6 – 30.4 months) and the actuarial 12 and 24 months OS was 79% and 22% respectively. Eleven p (73%) remain locally controlled and median time to local progression (PFS) was 11.4 (range 4.5 – 30.4 months). The actuarial PFS at 12 and 24 months were 85% and 56% respectively. Pancreatic SBRT was well tolerated in our cohort of patients. No grade 3 or higher toxicity was observed. Six p (40%) developed grade 2 epigastric pain and/or grade 2 nausea/vomiting. Conclusion In our experience, gating SBRT for pancreatic tumor is a feasible and well-tolerated treatment. Most patients are free from local progression, but overall survival remains poor. Prospective studies are needed to define the role of SBRT for pancreatic tumors. EP-1253 Interobserver variability in the target delineation of hepatocellular carcinoma. E. Gkika 1 , S. Tandini-Lang 2 , S. Kirste 1 , P. Holzner 3 , H.P. Neeff 3 , H.C. Rischke 4 , T. Reese 5 , F. Lohaus 6 , M.N. Duma 7 , K. Dieckmann 8 , R. Semrau 9 , M. Stockinger 10 , D. Imhoff 11 , N. Kremers 12 , M. Häfner 13 , N. Andratschke 2 , U. Nestle 1,14 , A.L. Grosu 1,14 , M. Guckenberger 2 , T. Brunner 1,14 1 University Hospital Freiburg, Radiation Oncology, Freiburg, Germany 2 University Hospital Zürich, Department of Radiation Oncology, Zurich, Switzerland 3 University Hospital Freiburg, Department of Visceral Surgery, Freiburg, Germany