ESTRO 2020 Abstract book

S689 ESTRO 2020

(less than 5) in mRCC patients after local surgery or during systemic therapy; (2) surgery or other local therapies not feasible; and (3) any contraindication to receive systemic therapy (such as comorbidities); (4) all the histologies were included; (5) available signed informed consent form for treatment. Tumor response and toxicity were evaluated using the Response Evaluation Criteria in Solid Tumors and the Common Terminology Criteria for Adverse Events version 4.03, respectively. Progression free-survival in field and out field (PFS-in field and out-field) and overall survival (OS) were calculated via the Kaplan-Meier method. The drug treatment free interval was calculated from the start of SBRT to the beginning of any systemic therapy. Results From January 2012 to December 2018, 61 patients with extracranial and cranial metastatic RCC underwent SBRT on 83 lesions. 73,8% of patients were treated for one metastatic lesion. Lympho-nodes, bone and brain metastases were included in the analysis. Median follow- up (range): 2.3 years (0-7.15). One- year PFS-in field was 70% (Figure 1), at 2-years 55%. One year PFS out field was 40%. One-year OS was 78%. Median RT dose was 25 Gy (range 10-52) in 5-10 fractions. Concomitant systemic therapy was used for only 11 patients, for the others 50 the drug treatment free rate was of 70% and 50% at one year and two years respectively (Figure 2). No acute and late toxicities were reported. Conclusion The pattern of failure was pre-dominantly out of field, even if the population was negatively selected and the used RT dose could be considered palliative. So SBRT seems to be a feasible and safe approach in oligometastatic RCC patients with an excellent PFS-in field and well tolerated. SBRT might play a role in the management of selected RCC patients allowing for a delay in the start of a systemic therapy. PO-1219 Primary Bladder Sarcoma: a multi- institutional experience from the Rare Cancer Network. P. BettolI 1 , Z. Liu 1 , N. Jara 2 , C.H. Fong 1 , W. Wong 3 , M. Terlizzi 4 , P. Sargos 4 , T. Zillie 5 , J. Thariat 6 , G. Ploussard 7 , S. Goyal 8 , P. Chung 1 , A. Berlin 1 , C. Sole 2 1 Princess Margaret Hospital, Radiation Oncology, toronto, Canada ; 2 IRAM, Radiation Oncology, Santiago, Chile ; 3 Mayo Clinic, Radiation Oncology, Rochester, USA ; 4 Institute Bergonie, radiation Oncology, Bordeaux, France ; 5 Hospitaux Universiaires de Geneve, Radiation Oncology, Geneve, Switzerland ; 6 Centre Francoise Baclese, Radiation Oncology, Caen, France ; 7 La Croix du Sud Hospital, Radiation Oncology, Toulouse, France ; 8 George Washington University Hospital, Radiation Oncology, Washington DC, USA Purpose or Objective Primary sarcoma of the urinary bladder (SUB) is a rare but aggressive form of bladder cancer (BCa), comprising less than 1% of all BCa. Available evidence on SUB is limited to case reports and small series. Therefore, management of SUB is usually extrapolated from approaches for urothelial carcinoma (UC). The aim of the present multi-institutional study is to assess clinical features, treatments, and outcomes of patients with SUB. Material and Methods Using a standardized database, 7 institutions retrospectively collected demographics, risk factors, clinical presentation, treatment modalities and follow-up data on patient with SUB between January 1994 and September 2019. Main inclusion criteria included BCa with soft tissue tumour histologies and sarcomatoid differentiations. Results Fifty-three patients (38 men and 15 women) were identified. Median follow up was 18 months (range 1-263).

Conclusion Concurrent NIVO plus SBRT appears to be well tolerated, without increased rates of severe toxicity. Definitive data of efficacy and toxicities of immunotherapy in combination with radiotherapy are not yet mature, but will be hopefully provided soon. PO-1218 Oligo Metastatic renal cell carcinoma: SBRT, if, when and how? G. Marvaso 1 , G. Corrao 1 , O. Oneta 1 , S.G. Gugliandolo 1 , M. Pepa 1 , A. Cecconi 1 , S. Gandini 2 , G. Piperno 1 , M. Cossu Rocca 3 , E. Verri 3 , G. Aurilio 3 , F. Corso 2 , D. Cullurà 3 , E. Rondi 4 , S. Vigorito 4 , F. Nolè 3 , R. Orecchia 5 , B.A. Jereczek- Fossa 1 1 IEO- European Institute of Oncology IRCCS, Division of Radiotherapy, Milan, Italy ; 2 IEO- European Institute of Oncology IRCCS, Department of Experimental Oncology, Milan, Italy ; 3 IEO- European Institute of Oncology IRCCS, Division of Medical Oncology, Milan, Italy ; 4 IEO- European Institute of Oncology IRCCS, Unit of Medical Physics, Milan, Italy ; 5 IEO- European Institute of Oncology IRCCS, Scientific Direction, Milan, Italy Purpose or Objective Renal cell carcinoma (RCC) have traditionally been considered radioresistant with a limited role for conventional fractionation as a local approach but since the appearance of stereotactic body radiation therapy (SBRT), radiotherapy (RT) has been increasingly employed in the management of metastatic RCC (mRCC). The aim of this study was to evaluate the role of SBRT for synchronous and metachronous oligo-metastatic RCC patients in terms of local control, delay of systemic treatment, overall

survival and toxicity. Material and Methods

Monocentric retrospective data collection from a single institution was performed. The inclusion criteria were as follows: (1) oligo-recurrent or oligo-progressive disease