ESTRO 2023 - Abstract Book

S769

Monday 15 May 2023

ESTRO 2023

Figure 1 CTCAE v4.0 and v5.0 (A) genitourinary (GU) and (B) gastrointestinal (GI) toxicity by timepoint for the once weekly (QW) and the semi-weekly (BIW) schedule. Grade ≥ 2 = grade 2 or worse adverse event. Conclusion The OTT of focal boosted prostate SBRT may safely be reduced from 29 days to 15 days in patients with intermediate- and high-risk PCa, given no grade ≥ 3 GU or GI toxicity was reported in both treatment groups. Based on the comparison between the QW and BIW schedule, patients should be counselled regarding the short-term advantages of a more protracted schedule. OC-0923 Every-other-day vs once-a-week urethra-sparing prostate SBRT: 5-year results of a randomized trial T. Zilli 1,2 , S. Jorcano 3 , S. Bral 4 , Z. Symon 5 , C. Rubio 6 , A. Bruynzeel 7 , R. Ibrahimov 8 , H. Minn 9 , A. Oliveira 10 , A. Bertaut 11 , G. Constantin 11 , R. Miralbell 12 1 IOSI, EOC, Radiation Oncology, Bellinzona, Switzerland; 2 University of Geneva, Faculty of Medicine, Geneva, Switzerland; 3 Teknon Oncologic Institute, Radiation Oncology, Barcelona, Spain; 4 Onze-Lieve-Vrouwziekenhuis, Radiation Oncology, Aalst, Belgium; 5 Sheba Medical Center, Radiation Oncology, Ramat Gan, Israel; 6 Hospital Universitario Sanchinarro, Radiation Oncology, Madrid, Spain; 7 VU University Medical Center, Radiation Oncology, Amsterdam, The Netherlands; 8 Neolife Medical Center, Radiation Oncology, Istanbul, Turkey; 9 University Hospital Turku, Radiation Oncology, Turku, Finland; 10 Portuguese Institut of Oncology, Radiation Oncology, Porto, Portugal; 11 Centre Georges François Leclerc, Statistics, Dijon, France; 12 Teknon Oncologic Institute, Radiation Oncology, Barcellona, Spain Purpose or Objective To present the 5-year results from a prospective multicenter phase II randomized trial of every-other-day (EOD) vs. once a-week (QW) urethra-sparing stereotactic body radiotherapy (SBRT) for localized prostate cancer (PCa). Materials and Methods Between 2012 and 2015, 170 patients from nine European institutions with cT1c-3aN0M0 PCa were randomized to 36.25 Gy in 5 fractions (7.25 Gy/fraction to the CTV; 6.5 Gy/fraction to the urethra) delivered either EOD (arm A, n=84), or QW (arm B, n=85). 82 patients from arm A and 83 from arm B were retained for the analysis (5 out of 170 randomized patients were never treated). The median follow-up time for the 170 randomized patients was 78 months (range, 3-110) and 77 months (range, 0-110 months) for arms A and B, respectively.