ESTRO 2020 Abstract Book

S638 ESTRO 2020

Results A total of 115 pts with mUC, 96 men (83,5%), median age 68 years old, 95 pts (82.6%) with ECOG 0-1, bladder primary in 101 (87.8%), transitional histology in 103 pts (89.6%), were treated with ICIs because of metastaic progression. Nodal progressive disease was present in 88 pts (76.5%), lung metastases (met) in 45 (39.1%), liver met in 23 (20%) and bone met in 27 (23.5%). RLT previously performed to ICIs was a radical cystectomy in 62 (53.9%) and radical radiotherapy in 7(6.1%). In 46 pts (40%) no RLT was done. ICIs prescribed were atezolizumab (55.7%), pembrolizumab (16.5%), durvalumab (11.3%), durvalumab/tremelimumab (7.8%), nivolumab (5.2%) and avelumab (3.5%). Median OS was 11.23 mo (95% IC; 6.02-16.44) and 7.95 mo (95%IC; 5.15-10.75) for group A and group B, respectively (P=0.481). Progression Free Survival (PFS) was 5.29 mo (95%IC; 2.01-8.56) for the RLT group vs 2.62 mo (95% IC; 1.20-4.04) for the non local treatment pts (P=0.306). The disease control rate (CR [6.9%] +PR [9.6%] +SD [14.1%]) was higher for pts with previous RLT compared to those pts who did not receive RLT (CR [3.2%] + PR [5.8%] + SD [6.4%], this difference was no statically significant (P=0.325). Conclusion Despite the results did not meet statistical significance, these are hypothesis generating and might suggest that RLT could play a role in the outcome of pts with mUC treated with ICIs. The true value of this approach remains to be demonstrated in prospective studies PO-1211 Stereotactic radiotherapy combined with immune- or targeted therapy for renal cell cancer patients. S. Kroeze 1 , C. Fritz 1 , S. Siva 2 , K.H. Kahl 3 , N. Sundahl 4 , O. Blanck 5 , D. Kaul 6 , A.L. Grosu 7 , J.J.C. Verhoeff 8 , G. Skazikis 9 , F. Roeder 10 , M. Geier 11 , F. Eckert 12 , M. Guckenberger 1 1 University Hospital Zürich, Radiation Oncology, Zurich, Switzerland ; 2 Peter MacCallum Cancer Centre, Radiation Oncology, Melbourne, Australia ; 3 University Hospital Augsburg, Radiation Oncology, Augsburg, Germany ; 4 University Hospital Ghent, Radiation Oncology, Ghent, Belgium ; 5 University Medical Center Schleswig-Holstein, Radiation Oncology, Kiel, Germany ; 6 Charité-University Hospital Berlin, Radiation Oncology, Berlin, Germany ; 7 University Medical Center Freiburg, Radiation Oncology, Freiburg, Germany ; 8 University Medical Center Utrecht, Radiation Oncology, Utrecht, The Netherlands ; 9 Schwarzwald-Baar Klinikum, Radiation Oncology, Villingen-Schwenningen, Germany ; 10 University Hospital Munich, Radiation Oncology, Munich, Germany ; 11 Ordensklinikum Linz, Radiation Oncology, Linz, Austria ; 12 University Hospital Tübingen, Radiation Oncology, Tübingen, Germany Purpose or Objective Approximately 2/3 of renal cell carcinoma (RCC) patients will present with, or develop metastatic disease. Treatment with tyrosine kinase inhibitors (TKI) or immune checkpoint inhibitors (ICI) has improved their prognosis significantly. However, when progression under these therapies occurs, second-line options usually show low response rates. Therefore, a multidisciplinary approach with a localized treatment is increasingly performed. Stereotactic radiotherapy (SRT) results in high local response rates and has now been included in the NCCN guidelines for mRCC patients. The aim of this study was to analyze the effectivity and safety of stereotactic radiotherapy (SRT) in mRCC patients receiving targeted- or immunotherapy. Material and Methods Data on mRCC patients was extracted from the retrospective international multicenter register study (TOaSTT) investigating SRT concurrent (≤30d) to TKI/ICI.

Overall survival (OS), progression free survival (PFS), local control (LC) and time to switch of systemic therapy after SRT were analyzed using Kaplan-Meier curves and log rank testing. Independent clinical factors influencing OS and PFS were analyzed using multivariate cox regression. Acute and late SRT-induced toxicity was defined by the CTCAE v4.03 criteria. Results Data of 128 SRTs in 53 mRCC patients was included, median follow-up was 12mo. Median age was 61 (range 38- 84)y, 49% had initially synchronous- and 51% metachronous metastatic disease. Multiorgan metastatic disease was present in 65%, and 52% had brain metastases at time of SRT. 89% had an ECOG-PS ≤1. 77.4% of patients were under first line systemic therapy; 32% received ICI, 68% TKI. The time from start of TKI/ICI to SRT was median 4mo (range 5d-49mo). 37% paused the TKI for median of 14 (range 2- 21) days, ICI was not paused. A median of 1 (range 1-11) metastases were treated per patients, with a median BED 10 of 65Gy (range 40-129.4). OS, LC and PFS after 1y were 71%, 75% and 25%, respectively. The cause of death was tumor-related in 94% and never therapy-related. Having ≤5 lesions was an independent factor for OS (p=0.004, 95% CI 0.035-0.553) and PFS (p=0.004, 95% CI 0.165-0.717) in multivariate analysis. ECOG-PS was the only other independent factor for OS (p=0.001, 95% CI 0.001-0.351). Receiving TKI vs. ICI did not influence OS or PFS (p=0.329). Recurrences were treated with a new course of radiotherapy in 46% of patients. After 1y, 45% received the same systemic therapy as at the time of SRT. Acute grade 3 toxicity was observed in 4 patients, late grade 3 toxicity in 1 patient. No grade 4 or 5 toxicity were observed. Conclusion In this cohort, mRCC patients with a limited number of metastatic lesions and a good ECOG perfomance status showed a promising OS and PFS when SRT was given concurrently with TKI/ICI. These patients potentially benefit the most from SRT. SRT achieved a good local control and was characterized by a favorable safety profile when combined with TKI/ICI. PO-1212 SBRT in patients with oligometastatic renal cell carcinoma in the era of immunotherapy O.C. Güler 1 , P. Hurmuz 2 , B. Tilki 2 , G. Ozyigit 2 , B.A. Yildirim 3 , F. Akyol 2 , C. Onal 3 1 Baskent Universitesi Tip Fakultesi- Adana Hastanes, Radiation Oncology, Adana, Turkey ; 2 Hacettepe University, Radiation Oncology, Ankara, Turkey ; 3 Baskent University, Radiation Oncology, Adana, Turkey Purpose or Objective To investigate the effects of stereotactic radiotherapy (SRT) on local control or survival in oligometastatic renal cell cancer (RCC) patients in the era of immunotherapy. Material and Methods A total of 27 patients and 46 lesions treated between February 2008 and January 2019. 10 patients (37%) with de novo oligometastasis and 17 oligo-progressed patients (63%) during treatment or follow-up were candidates for analysis. Only patients with bone metastasis included this study with the aim of homogenous group. The diagnosis of metastasis was based on imaging studies. Histopathological verification was not mandatory. Kaplan- Meier analysis used for survival. Results Median follow up was 13 months. 15 patients (56%) were alive at last visit. Estimated median overall survival (OS) and progression-free survival (PFS) were 26.1 months and 15.4 months, respectively. When we stratified patients by changing or keeping same systemic treatment there was no significant difference between two groups for OS (median 20.9 months vs. 27.5 months, p=0.566) or PFS (median 15.4 months vs. 11.8 months, p= 0.816). 1-year OS, PFS and local control (LC) rates were 73%, 56% and 86%, respectively. Clinical or radiological progression was