ESTRO 2020 Abstract Book

S637 ESTRO 2020

weeks after the treatment. Local recurrence occurred in 6 patients, 5 of them were successfully treated with partial amputation. In one case, the local recurrence was combined with recurrence in inguinal node, the patient underwent partial penectomy, lymphadenectomy and radiotherapy, but shortly afterwards he died on duplicate lung cancer. One patient had a nodal recurrence successfully salvaged by lymphadenectomy. One patient developed a necrosis of the glans requiring partial amputation. Currently, there are 24 patients alive without signs of disease. One patient died of cardiac comorbidity, one died of duplicate lung cancer. Nineteen patients have a preserved penis (73%), 18 of them sexually active before treatment report satisfactory intercourse. Conclusion Hyperfractionated interstitial high-dose rate brachytherapy with 18 times 3Gy per fraction twice daily is promising method in selected patients with penile carcinoma and deserves further evaluation in larger prospective study. PO-1209 A novel liquid fiducial marker for image- guided adaptive radiotherapy in bladder cancer. M. De Ridder 1 , L.C. Gebrandy 2 , T.M. De Reijke 2 , K.A. Hinnen 3 , M.C.C.M. Hulshof 3 1 LUMC, Radiation Oncology, Leiden, The Netherlands ; 2 Amsterdam UMC, Urology, Amsterdam, The Netherlands ; 3 Amsterdam UMC, Radiation Oncology, Amsterdam, The Netherlands Purpose or Objective To optimize Image Guided Adaptive RadioTherapy (IGART) for bladder preservation in bladder cancer, fiducial markers at the margins of the bladder tumor are needed to improve the precision of planning and delivery. All currently available fiducial markers have disadvantages like migration (titanium and gold fiducials), fading during treatment (hydrogel) or blurring (lipiodol, see fig 1). So, there is a need for a safe, feasible, visible and positionally stable marker. BioXmark® is a novel liquid injectable and adherent fiducial marker. This study evaluated the clinical performance of BioXmark for IGRT of bladder cancer. Material and Methods Prospective, single center phase I-II trial, including 20 patients with muscle-invasive bladder cancer treated with chemo-radiotherapy (55 Gy/20 fractions). BioXmark® liquid markers were injected in an outpatient setting using a flexible cystoscope. Visibility and stability of BioXmark® liquid markers on CT and cone-beam CT (CBCT) were evaluated. Results In total 77 markers were implanted in 20 patients; 60 markers (78%) in 19 patients (95%) were visible on treatment planning CT-scan. Invisible markers at the CT scan were mainly encountered during the first 4 patients, suggesting a learning curve for the application of markers. All visible markers after CT-acquisition were still visible at the last CBCT at the same position, without any signs of migration or fading. In 15/20 (75%) of the patients, 3 or more markers were visible on CT and thereby applicable for an daily automatic matching procedure. No BioXmark® related adverse-events were reported.

BioXmark fiducials markers at the tumorborders on a CT scan showing at the borders of a bladder tumor.

two examples of blurring\diffuse spreading of lipiodol through the bladder wall, inaccurate for delineating purposes. Conclusion The novel BioXmark® liquid fiducial marker appears to be safe, easy injectable, stable over time and showed sustained visibility in the use for daily-online adaptive IGRT for bladder preserving chemoradiotherapy in muscle- invasive bladder cancer. PO-1210 Local treatment on the outcome of immune- checkpoint inhibitors in metastatic urothelial carcinoma J. Maldonado 1 , R. Morales Barrera 2 , N. Vidal 3 , N. Feltes 4 , M. Domenech 5 , J. Puente 3 , M. Figols 5 , M. González 2 , F. Lozano 6 , H. López 5 , E. Gallardo 7 , D. Moreno 1 , C. Suárez 2 , J. Morote 6 , J. Carles 2 , J. Giralt 1 1 Hospital Universitario Vall d'Hebron, Radiation Oncology, Barcelona, Spain ; 2 Hospital Universitario Vall d'Hebron, Medical Oncology, Barcelona, Spain ; 3 Hospital Universitario Puerta de Hierro, Medical Oncology, Madrid, Spain ; 4 Hospital de Terrassa, Radiation Oncology, Terrassa, Spain ; 5 Althaia_ Hospital Sant Joan de Deu, Medical Oncology, Manresa, Spain ; 6 Hospital Universitario Vall d'Hebron, Urology, Barcelona, Spain ; 7 Hospital Universitari Parc Taulí, Medical Oncology, Sabadell, Spain Purpose or Objective Immune checkpoint inhibitors(ICIs) bring patients (pts) with metastatic urothelial carcinoma (mUC) to new scenarios. Moreover recent retrospective studies have reported the potential benefit of radical local (RLT) treatment to primary bladder cancer in pts with metastatic disease. We evaluate if a previous RLT in pts with mUC treated with ICIs impacts in the outcome Material and Methods Data from a multi-institutional database of pts with mUC treated with ICIs was evaluated from May 2013 to May 2019. Stratification was made according previous RLT with ICIs versus no RLT with ICIs. RLT was defined as radical surgery or external beam radiotherapy (>50 Gy) delivered to the bladder. A descriptive analysis was performed to assess oncologic outcomes. The X 2 test was used to determine differences in rates. Overall survival (OS) in previously RLT pts plus ICIs (group A) versus no RLT pts plus ICIs (group B) was generated using Kaplan-Meier method and results were compared with a log-rank test. OS was calculated from the date of initiation of ICI to the date of death. Analyses were performed using SPSS v21