ESTRO 2020 Abstract Book

S642 ESTRO 2020

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). Median age at presentation was 69 years (range 16-89).

Twenty-six percent of patients had a prior history of pelvic RT, and 37% were previous smokers. Main presenting symptoms at diagnosis were hematuria (52%), pelvic pain (27%), and both (10%). AJCC 8 group stage II, III and IV at diagnosis were 21%, 63% and 16%, respectively. Treatment modalities included surgery alone (45%), surgery plus neo- or adjuvant-chemotherapy (17%), surgery neo- or adjuvant-RT (11%), RT with concurrent chemotherapy (4%), neoadjuvant chemotherapy plus surgery plus adjuvant RT (2%) and palliative treatment (21%). Rates of local and distant recurrences were 49% and 37%, respectively. Five-year OS and PFS were 66.5% and 37.6% respectively. Median PFS for T2-category was not reached and for T3-T4 was 8.4 months (p=0.059). No statistically significant differences in PFS between treatment modalities were observed. Conclusion Primary SUB is an heterogeneous disease group, commonly presenting at advanced stages and exhibiting aggressive disease trajectory. Contrasting with UC, the primary pattern of recurrence of SUB is local, suggesting the need for multimodal approaches. Continuous international collaborative efforts seem warranted to provide guidance on how to best tailor treatments based on SUB-specific indices. PO-1220 Organ-preserving treatment for muscle- invasive bladder cancer: outcomes and prognostic factors M. Franckena 1 , N. Verschoor 2 , J. Boormans 3 , W. Heemsbergen 4 1 Erasmus Medical Center Rotterdam Daniel den Hoed Cancer Center, Department of Radiation Oncology, Rotterdam, The Netherlands ; 2 Erasmus Medical Center Rotterdam, Radiation Oncology, Rotterdam, The Netherlands ; 3 Erasmus MC Medical Center, Urology, Rotterdam, The Netherlands ; 4 Erasmus MC Medical Center, Radiation Oncology, Rotterdam, The Netherlands Purpose or Objective Objective: Organ-preserving treatment strategies (OPTS) for localized muscle invasive bladder cancer has become an acceptable alternative in selected patients instead of the standard of radical cystectomy. Clinical experience from large patient series is currently limited. Here we report on the outcomes and prognostic factors of OPTS, which may further guide treatment decisions in the context of the aging bladder cancer population where careful weighing of costs and benefits of treatment options will have to be made by both patient and physician. Material and Methods We performed a single-center retrospective cohort study comprising 248 patients with bladder cancer (T1-4N0M0), receiving external beam radiotherapy, preferably with radio- sensitizing chemotherapy (5FU/MMC) between 01- 2010 and 12-2017 at Erasmus Medical Center Rotterdam. Patients received 66 Gy in 33 fractions but for less fit patients, 63 Gy in 28 fractions was offered. We evaluated local control, acute treatment-related gastro-intestinal and genito-urinary toxicity (CTCAE V4), and survival. Results Median follow-up was 19.7 months (range: 0-60). Ninety- five % of patients completed treatment. As expected, median age, WHO performance status (WHO-PS) and Charlson Comorbidity index increased going from most preferred to least OPTS. Major tumor-related prognostic factors (tumour stage, tumor grade and presence of hydronephrosis) were equally distributed over subgroups. Local control (LC) and overall survival (OS) for the 66 and 63 Gy groups (n = 97 and n = 67) was significantly worse compared to the CRT-group (n=84), also after adjustment for disease characteristics. LC rates at 2 years were 81 %, 58 %, and 46 % respectively. OS rates at 2 years were 70 %, 48 %, and 37% respectively. We identified WHO-PS, Age as significant prognostic factors for local control (table 1).