ESTRO 2020 Abstract book

S687 ESTRO 2020

Historically, the entire empty bladder is included in a single clinical target volume (CTV). An empty bladder aims to reduce dose to organs at risk and improve reproducibility. Advances in imaging and radiotherapy techniques allow visualisation of the bladder wall and delivery of higher radiation dose to the tumour bed. Such techniques require bladder-filling to separate bladder walls for tumour bed boost. We evaluate the impact of bladder size in radiotherapy planning (RTP) scans on outcomes. Material and Methods This retrospective study included all patients treated with radical chemoradiotherapy for urothelial carcinoma of the bladder in a tertiary cancer centre from 2010 to 2014. An empty bladder imaging and treatment protocol was used. The whole bladder and extravesicle extension of tumour was treated to a uniform dose of 52.5Gy in 20 fractions with weekly chemotherapy. Bladder volume was measured on RTP scan. Overall survival (OS) was defined as time from start of treatment to death and patients still alive were censored at time last known alive. Progression free survival (PFS) was defined as time to local or metastatic recurrence. Cox proportional hazard ratio was used to investigate the association of bladder volume with outcomes. Results 132 patients were included in this study. One patient had high grade T1 disease and all others had muscle-invasive cancers. None had distant metastases. 5 patients did not complete radiotherapy but all had at least 16 of planned 20 fractions. 79 patients had neoadjuvant chemotherapy. With a median follow up of 74.1 months, the median OS of patients was 73.2 months (58.7-108.4). Median PFS was 64.3 months (35.5-108.4). Mean bladder volume was 109.50cm 3 (39.2- 433.3). Due to the large range of bladder volumes, a log scale was used. Larger log(bladder volume) on RTP scan was associated with poorer OS (HR 1.78 p=0.03) and PFS (HR 1.71 p=0.03). This is not clinically significant after multivariate analysis. (Table 1).

PO-1214 Stereotactic Body Radiation Therapy in the management of oligometastases from urothelial cancer. C. Franzese 1,2 , G. Francolini 3 , L. Nicosia 4 , F. Alongi 4,5 , L. Livi 3,6 , M. Scorsetti 1,2 1 Humanitas Research Hospital, Radiotherapy and Radiosurgery, Rozzano Milan, Italy ; 2 Humanitas University, Department of Biomedical Sciences, Milan, Italy ; 3 Azienda Ospedaliero-Universitaria Careggi, Radiation Oncology Unit, Firenze, Italy ; 4 IRCCS Sacro Cuore Don Calabria Hospital, Advanced Radiation Oncology Department, Negrar, Italy ; 5 University of Brescia, Radiotherapy unit, Brescia, Italy ; 6 University of Florence, Departments of Biomedical- Experimental- and Clinical Sciences- Radiation Oncology Unit., Firenze, Italy Purpose or Objective Bladder cancer represents the most common type of urothelial carcinoma with poor prognosis in case of metastatic disease. Chemotherapy represent the standard of care for metastatic setting, with a median overall survival (OS) of 12.5 - 15 months. In the present study we aimed to evaluate the role of stereotactic body radiation therapy (SBRT) in the management oligometastatic urothelial cancer. Material and Methods Data were collected from three Institutions to include patients with diagnosis of bladder or other urothelial cancer that developed maximum 5 synchronous or metachronous metastases. Concomitant systemic therapy was allowed. Patients were treated both with Linac or robotic-arm based SBRT. Tumour response was classified according to EORTC-RECIST criteria version 1.16. End points of the present study were the outcome in terms of Local control of treated metastases (LC), out-field progression free survival (dPFS), overall progression free survival (PFS) and OS. Results A total of 82 lesions in 61 patients were treated. Primary tumour was located in bladder in 50 (82%) patients, followed by kidney pelvis (7; 11.5%) and ureter (3; 4.9%). Most common sites of metastatic disease were lung (40.2%) and lymph nodes (35.4%). Twenty-nine patients (47.5%) received 1 to 3 lines of systemic therapy before RT and fourteen (23%) patients had systemic therapy during SBRT. Median BED 10 value was 78.7 Gy (range 37.5 – 151.2). Median follow-up was 17.2 months. Rates of LC at 1 and 2 year were 92% and 88.9%, respectively. Systemic therapy previous to SBRT was predictive of LC (HR 2.62, p = 0.034). Rates of PFS at 1 and 2 year were 47.9% and 38.1%. High number of metastases was negative predictive factor of PFS (HR 2.65, p=0.008). Median OS was 25.6 months. Rates of OS at 1 and 2 year were 78.9% and 50.7%. Total delivered dose (HR 0.93, p= 0.003) and BED 10 (HR 0.97, p=0.006) were correlated with OS. No > grade 2 adverse events were reported in this cohort. Conclusion SBRT represents an effective and safe treatment in the oligometastatic setting from urothelial carcinoma. This local approach is potentially able to delay the onset of new systemic therapies with minimal alteration of patient’s quality of life. PO-1215 Impact of bladder size at radiotherapy planning scan on survival Y.P. Song 1 , A. Choudhury 2 , A. McPartlin 1 , P. Hoskin 2 , A. McWilliam 2 1 The Christie NHS Foundation Trust, Clinical Oncology, Manchester, United Kingdom ; 2 The University of Manchester, Radiotherapy Related Research, Manchester, United Kingdom Purpose or Objective Radiotherapy is the mainstay of curative treatment for bladder cancer patients opting for organ preservation.

Conclusion Advances in radiotherapy technique allow more precise treatment plans. As clinical trials adopt bladder-filling protocols, it is vital that the impact of bladder volume on clinical outcomes is considered. Our relatively small study shows that bladder volume is not related to survival in a multivariate analysis. Factors like hydronephrosis and CIS impact survival, and should be considered in formulation of management plans. Bladder volume in this study reflects poor bladder emptying which may differ from planned bladder filling. Further evaluation in a prospective patient cohort with planned bladder filling will improve our understanding of the impact of bladder size on outcomes in the modern era.