ESTRO 2020 Abstract book

S686 ESTRO 2020

observed in 4 irradiated lesions at first year. There was no grade 3 or more acute or late toxicity in the study cohort. Conclusion By providing excellent local control and low toxicity profile, SRT is an effective treatment in oligometastatic RCC patients. The clinical outcomes did not significantly differ for patients who were treated with SRT and received same systemic chemotherapeutic or immunotherapy agent. PO-1213 Pelvic radiotherapy in node positive bladder cancer – outcomes in a selected cohort M. Tjong 1 , I. Lunsky 1 , K. Ajib 2 , S.S. Sridhar 3 , N. Fleshner 2 , A. Zlotta 2 , A. Berlin 1 , G.S. Kulkarni 2 , P. Chung 1 1 Princess Margaret Cancer Centre, Radiation Oncology, Toronto, Canada ; 2 Mount Sinai Hospital, Surgical Oncology, Toronto, Canada ; 3 Princess Margaret Cancer Centre, Medical Oncology, Toronto, Canada Purpose or Objective The presence of clinical nodal metastases in bladder cancer is associated with poor prognosis such that many patients are managed with primary chemotherapy alone without local therapies. Radical cystectomy for local disease control has been reported to be associated with better than expected outcomes especially in those that demonstrate chemo-responsiveness. Radiotherapy (RT)- based treatment in node-negative bladder cancer is gaining wider acceptance for selected patients. However, few data exist using such an approach in patients with nodal metastases (cN+). We examined outcomes in clinically node-positive bladder cancer patients treated with radical radiotherapy. Material and Methods Characteristics, treatment details and outcomes of urothelial bladder patients with cT2-4, cN1-3, cM0 disease treated between January 2003 and April 2017 were retrospectively collected and analyzed. Patients treated with a pelvic dose of less than 50 Gy were excluded. Pelvic locoregional control was defined as absence of pelvic disease, excluding intravesical superficial recurrences. Results A total of 25 patients (6 females) with median age of 67 years (range 51-89) met inclusion criteria. Median ECOG performance status was 1 (range 0-2). Of these 17 were cT2 (9 cN1, 5 cN2, 3 cN3), 3 were cT3 (all cN1), and 5 cT4 (4 cN1, 1 cN2). All patients underwent maximally feasible transurethral resection of bladder tumor (TURBT). Post- TURBT, RT (including bladder boost) was delivered to a median dose of 64 Gy (50-66) in 32 (20-33) fractions. Five were medically unfit for any chemotherapy, 6 had concurrent chemoradiation only, 5 neoadjuvant or consolidation only, and 9 neoadjuvant plus concurrent chemotherapy. Median follow-up was 3.2 years (range 0.2- 9.7), 6 (24%) patients lost to follow-up before 1 year. At three years, overall survival (OS) was 91% (95% Confidence Interval (CI): 69-98%), distant metastasis-free survival (DMFS) was 72% (95% CI: 47-86%), and pelvic locoregional control (PLC) was 84% (95% CI: 57-95%). Of 6 with pelvic failures, 3 had bladder only, 2 had nodal only and one patient had both. Of these, one patient underwent salvage radical cystectomy (RC) post-RT for isolated bladder Overall outcomes were good for this selected cohort of cN+ bladder cancer patients with acceptable pelvic local control rates. With caveat of short follow-up (24% lost to follow-up before 1 year) this suggests that RT-based treatment, similar to surgery may be a reasonable approach for improving pelvic and overall disease control outcomes in selected patients. recurrence. Conclusion

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