ESTRO 36 Abstract Book

S277 ESTRO 36 _______________________________________________________________________________________________

13 University Hospital Würzburg, Department of Radiation Oncology, Wuerzburg, Germany 14 University Hospital Halle, Department of Radiation Oncology, Halle, Germany 15 University Hospital Basel, Department of Radiation Oncology, Basel, Switzerland 16 University Medical Center Hamburg-Eppendorf, Department of Radiation Oncology, Hamburg, Germany 17 Strahlenzentrum Hamburg, Department of Radiation Oncology, Hamburg, Germany 18 University Hospital of Cologne, Department of Radiation Oncology, Cologne, Germany 19 Klinikum Passau, Department of Radiation Oncology, Passau, Germany Purpose or Objective Stereotactic body radiation therapy (SBRT) is applied in the oligometastatic setting to treat liver metastases. However, factors influencing tumor control probability (TCP) other than radiation dose have not been thoroughly investigated. Here we set out to investigate such factors with a focus on the influence of histology and chemotherapy prior to SBRT using a large multi-center database from the German Society of Radiation Oncology. Material and Methods From 17 german and swiss radiotherapy centers, data on all patients treated for liver metastases with SBRT since its introduction in 1997 has been collected and entered into a centralised database as an effort of the SBRT task group of the DEGRO. 452 SBRT treatments in 363 patients were analysed after retrieval of patient, tumor and treatment data from the aforementioned multi-center database. Histolgy was considered through random effects in semi- parametric and parametric frailty models. Dose prescriptions were parametrized by conversion to the biologically effective dose at the isocenter (BED max ) using the LQ formalism. Results After adjusting for histology, BED max was the strongest predictor of TCP. Larger PTV volumes, chemotherapy prior to SBRT and non-advanced motion management techniques predicted significantly lower TCP. For an average metastasis, the model predicted a BED of 208±76 Gy 10 necessary for 90% TCP at 2 years with no prior chemotherapy, but 292±109 Gy 10 when chemotherapy had been given. Breast cancer metastases were significantly more responsive to SBRT with 90% TCP at 2 years achieved with BED max of 178±65 Gy 10 or 94±55 Gy 10 with and without prior chemotherapy, respectively. There was a tendency that colorectal metastases had an inferior TCP. Conclusion Besides dose, histology and pretreatment chemotherapy were important factors influencing local TCP in this large cohort of liver metastases. After adjusting for prior chemotherapy, our data adds to the emerging evidence that breast cancer metastases do respond better to hypofractionated SBRT compared to other histologies. OC-0524 Phase II trial on SBRT for Liver Metastases: Long-term outcomes and prognostic factors of survival. T. Comito 1 , C. Franzese 1 , E. Clerici 1 , A. Tozzi 1 , C. Iftode 1 , P. Navarria 1 , G.R. D'Agostino 1 , D. Franceschini 1 , F. De Rose 1 , A. Ascolese 1 , L. Di Brina 1 , S. Tomatis 1 , M. Scorsetti 1 1 Istituto Clinico Humanitas, Radiotherapy and Radiosurgey, Rozzano Milan, Italy Purpose or Objective Liver is a common site of metastases for several cancers. In selected patients with oligometastatic disease confined to liver, surgical resection improves overall survival (OS). Approximately 70–90% of liver metastases, however, are unresectable and a safe and effective alternative therapeutic option is necessary for these patients. The aim of this study was to evaluate long-term

Purpose or Objective To determine the maximum tolerated dose (MTD) of fractionated extracranial stereotactic radiotherapy (ESRT) to lymph nodal recurrences in different clinical settings. Material and Methods Patients enrolled in a phase I clinical trial entered the analysis. Each enrolled subject was included in a different study arm, according to nodal site and previous treatment. Dose has been prescribed according to ICRU 62. A four no-coplanar beams class solution or a volumetric technique (VMAT) have been applied in all patients. The planning target volume (PTV) has been defined as gross tumour volume (GTV) plus 5-15 mm. According to different arms, patients received an ESRT dose ranging from 20 Gy up to the maximum planned dose of 50 Gy in 5 fractions. Dose-limiting toxicity (DLT) was any grade > 3 acute toxicity or any grade > 2 late toxicity. The MTD was exceeded if 2 of 6 or 4 of 12 patients in a cohort experienced DLT. Results 101 patients (M/F: 47/54; median age 67 years, range 43- 87years) with 128 nodal lesions were treated. were treated. Of these, 48 (37.5%) were nodal recurrences in neck or chest, 34 (26.5%) were in abdomen and 46 (35.9%) were in pelvis. The primary tumour was most frequently gynaecologic cancer (44%), followed by genito-urinary cancer (22%), gastro-intestinal (13%), lung (13%) and other (9%). The median ESRT delivered dose was 35 Gy (20-50) in five fractions. With a median follow up of 19 months (4- 104), the overall response rate was 88% (CI95: 80-93.6; Complete Response: 68%; Partial Response: 20%), with only 5% of patients developing disease progression. No DLT was recorded in this group of patients. Two- and 4-year local control were 81% and 70.2%, respectively. Two- and 4-year metastases free survival were 43.5% and 30.9%, respectively. Conclusion In quite varied setting of lymph nodal recurrences an ESRT treatment in five fractions up to a dose of 50 Gy is safe and well tolerated. OC-0523 SBRT for oligo-metastatic liver disease–effect of chemotherapy and histology on local tumor control R. Klement 1 , M. Guckenberger 2 , H. Alheid 3 , M. Allgaeuer 4 , G. Becker 5 , O. Blanck 6 , J. Boda-Hegemann 7 , T. Brunner 8 , M. Duma 9 , S. Gerum 10 , D. Habermehl 11 , G. Hildebrandt 12 , V. Lewitzki 13 , C. Ostheimer 14 , A. Papachristofilou 15 , C. Petersen 16 , T. Schneider 17 , R. Semrau 18 , S. Wachter 19 , N. Andratschke 2 1 Leopoldina Hospital Schweinfurt, Department of Radiation Oncology, Schweinfurt, Germany 2 University Hospital Zürich, Department of Radiation Oncology, Zurich, Switzerland 3 Strahlentherapie Bautzen, Department ofRadiation Oncology, Bautzen, Germany 4 Krankenhaus Barmherzige Brüder, Department of Radiation Oncology, Regensburg, Germany 5 RadioChirurgicum CyberKnife Südwest, Department of Radiation Oncology, Goeppingen, Germany 6 Universitätsklinikum Schleswig-Holstein, Department of Radiation Oncology, Kiel/Lübeck, Germany 7 University Hospital Mannheim /University of Heidelberg, Department of Radiation Oncology, Mannheim, Germany 8 University Hospital Freiburg, Department of Radiation Oncology, Freiburg, Germany 9 Klinikum rechts der Isar- Technische Universität München, Department of Radiation Oncology, Munich, Germany 10 University of Munich – LMU Munich, Department of Radiation Oncology, Munich, Germany 11 University Hospital Heidelberg, Department of Radiation Oncology, Heidelberg, Germany 12 University Hospital Rostock, Department of Radiation Oncology, Rostock, Germany