ESTRO 2021 Abstract Book

S1117

ESTRO 2021

11 ng/ml and with a PCa, Gleason score 7 (4 + 3), cT2bN0M0.

Results In total, 242 respondents (62% residents or with ≤ 10 years as attending RO) completed the survey exploring their experiences in 56 countries (the most represented: USA: 22%; Spain: 14.5%; and India: 8.7%). Most don't recommend WPRT in this patient ( n = 168; 69.4%) because there is no evidence supporting its benefit (55.4%), it is not a high-risk PCa (34.5%), or it is not N1 (10.1%). The reasons for WPRT ( n = 74; 30.6%) are: the risk of lymph node metastasis is ≥ 15% (68.9%), it is an unfavorable intermediate-risk PCa (25.6%), or other (5.5%). The most used regimens to irradiate the prostate gland are: 3 Gy x 20 fractions (fr) (30.2%), 1.8 - 2 Gy x 37 - 45 fr (28,1%), or 2.5 Gy x 28 fr (26%). Most responders ( n = 156; 64.5%) irradiate the seminal vesicles (SV) with the same dose fractionation than that to prostate gland. Other dose/fr to irradiate the SV are: > 2 - 2.2 Gy/fr (36%), > 2.3 - 2.5 Gy/fr (20.9%), or 2.75 Gy/fr (12.8%). Those who irradiate pelvic lymph node areas use the following fractionation: 1.8 - 2 Gy/fr (45.6%) or 2.2 Gy/fr (10.7%). Conclusion Practice differs greatly between RT Departments, even within the same country. Most RO do not perform WPRT on intermediate-risk PCa. Clinical trials are needed to identify which subgroup of intermediate-risk PCa most likely to benefit from WPRT, and compare results from different dose fractionation. PO-1362 The prognostic value of PI-RADS score in ultra-hypofractionated radiotherapy for prostate cancer. M. Miszczyk 1 , Ł. Magrowski 1 , J. Rembak-Szynkiewicz 2 , P. Rajwa 3 , A. Namysł-Kaletka 4 , A. Paradysz 3 , A. Napieralska 4 , G. Woźniak 4 , G. Głowacki 4 , M. Stąpór-Fudzińska 5 , L. Miszczyk 4 1 Maria Sklodowska-Curie National Research Institute of Oncology, Third Radiotherapy and Chemotherapy Department, Gliwice, Poland; 2 Maria Sklodowska-Curie National Research Institute of Oncology, Radiology Department, Gliwice, Poland; 3 Medical University of Silesia, Urology Department, Zabrze, Poland; 4 Maria Sklodowska-Curie National Research Institute of Oncology, Radiotherapy Department, Gliwice, Poland; 5 Maria Sklodowska-Curie National Research Institute of Oncology, Radiotherapy Planning Department, Gliwice, Poland Purpose or Objective The Prostate Imaging Reporting and Data System (PI-RADS) v2.1, the standardized method of prostate MRI assessment, serves as a robust diagnostic tool for significant prostate cancer (PCa). Nevertheless, less is known about its prognostic role in radiotherapy for PCa. We aimed to investigate an association between PI- RADS score disease-free survival (DFS) and metastasis-free survival (MFS) in low- (LR) and intermediate-risk (IR) PCa patients treated with ultra-hypofractionated CyberKnife radiotherapy. Materials and Methods We retrospectively analysed 109 PCa patients (IR 49.5%; LR 50.5%), treated at a single institution with primary ultra-hypofractionated CyberKnife radiotherapy up to 36.25 Gy in 5 fx, to the prostate with a 5-mm margin. PI-RADS was assessed retrospectively by an experienced radiologist, who was blinded to oncologic outcomes. The association was analysed using the Kaplan-Meier estimates with log-rank testing, and Cox regression model for DFS and MFS. Results During a median follow-up of 54.4 (IQR 32.4-69.5) months, biochemical or clinical recurrence was observed in 9 patients (8.3%), and metastasis in 3 patients (2.8%). There were no significant differences in clinicopathologic factors between PI-RADS categories The PI-RADS was not significantly associated with the