ESTRO 37 Abstract book

S872

ESTRO 37

Purpose or Objective For renal cell carcinoma (RCC), surgery is standard of care. However, there is a need for non-invasive treatment alternatives like stereotactic body radiotherapy (SBRT). Nowadays, SBRT for RCC is mainly CT based with tumor delineation using CT and Cone-Beam CT (CBCT) guided dose delivery. SBRT for RCC could be optimized with the introduction of MR guided radiotherapy systems, like the MRI-Linac (MRL), in which real time MR imaging during dose delivery is possible. As a consequence of the introduction of MRI in the radiotherapy treatment of RCC, there is a need for guidelines on the delineation of RCC on MRI. In this study an RCC delineation guideline using MRI was developed and evaluated. Material and Methods Consecutive RCC patients underwent a contrast enhanced MRI scan. Five physicians received a MRI dataset (T2, pre- and post-contrast T1, DWI, and ADC), on which they contoured the tumor. On four datasets the tumor was delineated without instructions (development phase). With help of an expert radiologist new delineation guidelines were made based on these initial delineations. Next, another 10 new cases were delineated following these guidelines and subsequently evaluated (evaluation phase). The volumes, conformity index (CI) and distance between centers of the mass (dCOM) were calculated. Results Four RCC cases were delineated in the development phase and 10 RCC cases in the evaluation phase by 5 observers. The agreement between observers in the evaluation phase resulted in a mean CI of 0.77, ranging from 0.59-0.88. The mean dCOM was 0.55 mm. Conclusion A delineation guideline for RCC on MRI has been created, based on T2 weighted MR imaging with help of contrast enhanced T1 weighted imaging and DWI. Inter-observer delineation variations were limited. The recommenda- tions for contouring and sequences used can be helpful in the introduction of MRI guided radiotherapy in the clinic. EP-1618 Monoubiquitinylated histone H2B as a potential target in treatment resistant germ cell tumors C. Oing 1 , S. Dyshlovoy 1 , F. Honecker 2 , L. Nordquist 3 , K. Rothkamm 3 , C. Bokemeyer 1 , C. Petersen 4 , W.Y. Mansour 3 1 Universitaetsklinikum Hamburg-Eppendorf, Oncology- Hematology and Bone Marrow Transplantation with 3 Universitaetsklinikum Hamburg-Eppendorf, Laboratory of Radiobiology and Radiation Oncology, Hamburg, Germany 4 Universitaetsklinikum Hamburg-Eppendorf, Radiotherapy and Radiation Oncology, Hamburg, Germany Purpose or Objective To investigate the role of histone H2B monoubiquitination (H2Bub1) in treatment resistance and as a therapeutic target in treatment resistant germ cell tumors (GCTs). Up to 30% of patients with advanced GCT disease suffer from treatment-resistant disease and have a dismal prognosis. Treatment resistance is of multifactorial origin, where tissue differentiation and DNA repair alterations play critical roles. A better understanding of resistance mechanisms and identification of new therapeutic targets are urgently needed to improve outcomes. H2Bub1 is section of Pneumology, Hamburg, Germany 2 ZeTuP, Breast and Tumor Center, St. Gallen, Switzerland

EP-1616 Outcomes Following Primary Radiochemotherapy in Patients with Localy Advanced Bladder Cancer I. Albitskiy 1 , T. Aro 2 , T. Charas 1 , G. Amiel 2 , R. Ben Yosef 1 1 rambam medical center, radiation oncology, Haifa, Israel 2 rambam medical center, urology, Haifa, Israel Purpose or Objective Radical cystectomy is the treatment of choice for locally advanced invasive bladder cancer. External beam irradiation in combination with chemotherapy following endoscopic resection of the tumor is considered an alternative treatment for selected patients with small tumor burden or with contraindication for surgery because of performance status and co-morbidities. The aim of this study is to report on the outcome of patients treated with primary radiochemotherapy in our medical center. Material and Methods Retrospective analysis of bladder cancer patients receiving radiation therapy in our hospital between the years 2005-2015 Data collection included demographic information, tumor grade and stage at diagnosis, radiation therapy protocol, chemotherapy and survival. Results 155 patients with a diagnosis of bladder cancer were treated in our radiation therapy institute during the years 2005-2015. 94 patients completed a definitive radiation therapy (≥55Gy) for invasive bladder cancer. 43 patients received either cisplatin (20) or carboplatin (23) during the radiation period. Median age of the patients was 74.9 years (range 40.4 – 91.7 years), 83 males and 11 females. Mean follow up was 39.4 months. Overall survival for the entire cohort of patients was 39% in 5 years (median – 31.8 months). For those who were younger than 70y (no -28) the median overall survival was 63.6 months (52% the rate of 5-year survival, p=0.019). The median OS in the group of patients (no – 43) that received concomitant chemoradiation was 50.8 months vs 22.7 months in the group of radiotherapy (p=0.034).We studied influence of radiotherapy treatment parameters such as day dose (2Gy vs 1.8Gy)/total dose (60 Gy vs more than 60 Gy)/boost dose (≥ 16 Gy or less) on OS, but did not find statistical significance. Conclusion Radiation therapy for locally advanced bladder cancer in our series is effective as is in larger series reported in the literature although our patients were older and partially treated with concurrent chemotherapy. Radiochemotherapy should be indicated for those patients who cannot undergo radical cystectomy and might be offered as an alternative approach to surgery for appropriate patients. EP-1617 Development and evaluation of a MRI based delineation guideline for renal cell carcinoma F.M. Prins 1 , L.G.W. Kerkmeijer 1 , J.R.N. Voort van Zyp 1 , W.S.C. Eppinga 1 , H.D. Heerkens 1 , J.J.W. Lagendijk 1 , R.H.N. Tijssen 1 , E.P.A. Vonken 2 , A.N.T.J. Kotte 1 , M.M. Barendrecht 3 , W. Chu 4 , M.P.W. Intven 1 1 UMC Utrecht, Radiation Oncology, Utrecht, The Netherlands 2 UMC Utrecht, Radiology, Utrecht, The Netherlands 3 TerGooi Hospital, Urology, Hilversum, The Netherlands 4 Odette Cancer Centre- Sunnybrook Health Sciences Centre- University of Toronto- ON, Radiation Oncology, Toronto, Canada