ESTRO 36 Abstract Book

S668 ESTRO 36 2017 _______________________________________________________________________________________________

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 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. EP-1254 DVH analysis of radiotherapy of upper gastrointestinal tumours: a model to predict toxicity. G.C. Mattiucci 1 , L. De Filippo 1 , N. Dinapoli 1 , L. Boldrini 1 , S. Chiesa 1 , M. Bianchi 1 , R. Canna 1 , F. Cellini 1 , G. Chiloiro 1 , F. Deodato 2 , G. Macchia 2 , C. Indellicati 1 , D. Pasini 1 , A.G. Morganti 3 , V. Valentini 1 1 Università Cattolica del Sacro Cuore -Policlinico A. Gemelli, Radiotherapy, Rome, Italy 2 Fondazione di Ricerca e Cura “Giovanni Paolo II”- Università Cattolica del Sacro Cuore, Radiotherapy Unit, Campobasso, Italy 3 Department of Experimental- Diagnostic and Specialty Medicine – DIMES- Università di Bologna- Ospedale S. Orsola-Malpighi, Radiation Oncology Center, Bologna, Italy Purpose or Objective Tolerance of small bowel is the dose limiting factor in radiation therapy for abdominal neoplasms. Bowel constraints for treatment planning in abdominal radiotherapy derive from scientific publications of pelvic tumors. This study has the aim to evaluate dose tolerance of small bowel and to provide a model detecting acute toxicities in patients with upper gastrointestinal (GI) cancer treated with radiotherapy. Material and Methods Patients with upper GI cancer treated between 2009 and 2016 with 3D-conformal or intensity modulated radiotherapy (IMRT) with or without concomitant chemotherapy were enrolled in this study. Nausea, vomit and loss of weight, as acute upper gastrointestinal (GI) toxicities, were scheduled using CTCAE v4.03 scale. In all patients small bowel loops, bowel bag, liver and stomach, if present, were contoured by a radiation oncologist on simulation computed axial tomography according to QUANTEC guidelines. Liver, PTVs, Small Bowel, Bowel Bag and Stomach were selected on Dose Volume Histogram (DVH) and their data were extrapolated. DVHs were analyzed for this structures using R statistical software (http://www.R-project.org). Results Data of 143 patients with a median age of 66 years (range 35-84), 79 (55,2%) resected and 64 (44,8%) unresected, were analyzed. All patients selected had primary tumour location cancer in upper GI tract such as pancreas (53%), biliary ducts (15%), stomach (26%), gallbladder (3%), gastroesophageal junction (3%). Prescribed dose ranged between 3000 cGy and 5580 cGy with fractionaction ranging between 180 cGy and 300 cGy. Most of patients were treated with 3D conformal radiotherapy (92%) and only 8% received IMRT. Fiftytwo (36,4%) patients reported no upper GI toxicity; on 27 (18,9%), 36 (25,2%) and 28 (19,5%) patients were observed respectively grade 1, 2 and 3 toxicity. No grade 4 toxicity was recorded. Fiftyone patients discontinued radiotherapy and 9 did not complete it, none of them because of GI toxicities. Analizing VDose for upper GI toxicity grade ≥ 2 on DVHs, small bowel loops V31.7, bowel bag V32.7, liver V35.6 Gy and stomach V31.5 Gy resulted as the parameter which most influenced upper GI toxicity (p<0.05). Univariate analysis for ≥G3 grade upper GI toxicity for all structures was not statistically significant (p>0.05). Univariate analysis showed no impact of surgery on upper GI toxicity while female sex and concomitant chemotherapy were associated with likely upper GI toxicity. Multivariate logistic model showed liver V35.6 as best and unique predictor of GI toxicity grade ≥ 2 (p<0.01). Relation between dose and toxicity is summarized in figure 1 as empirical cumulative density function plot. Conclusion