ESTRO 2021 Abstract Book

S1081

ESTRO 2021

28 months, p= 0.04 and 46 vs 19 months, p=0.02 ), while worse MFS was significantly related to concomitant ADT (not reached vs 32 months, p=0,002). Both Gleason score > 8 and ongoing ADT showed to be independent predictors of BRFS (HR 2.42, 95%CI 1.09-5.41, p=0.02 and HR 2.83, 95%CI 1.17-6.8, p=0.02, respectively). Only ongoing ADT was confirmed as an independent predictor of MFS (HR 4.75, 95%CI 1.52-14.8, p=0.007). Regarding toxicity, late grade 1 and 2 rectal and bladder toxicity occurred in three (6%) and 13 (26%) patients, respectively. One patient experienced both grade 3 acute and chronic bladder toxicity. Conclusion Re-SBRT was confirmed to be safe and effective. Accurate selection criteria are needed to maximize therapeutic ratio of this treatment approach. PO-1317 Prostate Cancer Patient Reported Outcome After Cyberknife Robotic Radiosurgery S. Exner 1 , F. Fehlauer 1 1 Strahlenzentrum Hamburg, Cyberknife Unit, Hamburg, Germany Purpose or Objective The optimal management of localized Prostate Cancer (PC) should take account consideration of patient and clinical risk factors, as well as patient preferences. The objectives of this cohort study of men with newly diagnosed localized PC were to document side effects with the International Prostate Symptom Score (IPSS), International Consultation on Incontinence Questionnaire Short Form (ICIQ-SF), International Index of Erectile Function Questionnaire (IIEF-5) and as well Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events Questionnaire (PRO-CTCAE) following radiosurgery with the Cyberknife. Materials and Methods In this cohort analysis, 30 patients with localized prostate cancer were analyzed who received Cyberknife radiosurgery (5 x 7 Gy) and completed the IPSS (1-23), ICIQ-SF (0-17), IIEF-5 (6-24) and the German validated PRO-CTCAE questionnaires. Results Mean IPSS score was 6.9 (mild symptomatic), mean ICIQ-SF score was 3.3 (mild impairment of incontinence), mean IIEF-5 score was 17.0 (mild erectile dysfunction). The highest score at PRO-CTCAE was for urinate frequently (one patient, 5%), achieve and maintain erection (one patient, 3,3%), ejaculation problems (two patients, 6,7%) and decreased libido (one patient, 3,3%). There was no significant difference at follow-up period or treated prostate volume (F/U: > 1 vs. < 1 year; Volume ml: >64 vs. < 64). Local control and overall survival were 100%. No patient developed metastasis after radiosurgery. None of our patients died until now. Conclusion Robotic Cyberknife radiosurgery for localized prostate cancer shows good local control and overall survival with a very mild side effect profile reported by patients. PO-1318 salvage treatment outcomes in lymph node-positive prostate cancer patients after surgery D. Kim 1 , J. Kim 2 , S.K. Hong 3 , S. Byun 3 , S.E. Lee 3 1 Seoul National University Bundang Hospital, Radiation Oncology , Seongnam , Korea Republic of; 2 Seoul National University Bundang Hospital, Radiation Oncology, Seongnam, Korea Republic of; 3 Seoul National University Bundang Hospital, Urology, Seongnam, Korea Republic of Purpose or Objective The presence of lymph node invasion after surgery in prostate cancer is known as a poor prognostic sign. However, salvage treatment strategies for lymph node-positive (LNP) prostate cancer patients with persistence or recurrence of prostate-specific antigen (PSA) has not yet been clearly defined. In this study, we tried to evaluate salvage treatment options and outcomes in LNP prostate cancer. Materials and Methods We retrospectively reviewed 138 prostate cancer patients with LNP who underwent surgery between 2004 and 2018 at our institution. Ninety-four patients who received salvage treatment were included in the final analysis. Salvage treatment was based on the clinical judgment of the physician as follows: 37 (39.4%) patients were treated with androgen deprivation therapy (ADT) alone, and 57 patients (60.6%) were treated with a combination of ADT with radiotherapy (RT). In our study, we analyzed clinicopathological and treatment factors for biochemical failure (BCF)-free survival, clinical progression (CP)-free survival, and overall survival (OS). Results The median duration of follow-up was 55 months (range, 14–191). In terms of salvage treatment failure, ADT alone group showed higher incidence than ADT with RT group during the follow-up period (89.2% and 45.6%, respectively). The combination of ADT with RT was associated with better BCF-free survival than ADT alone (hazard ratio [HR]: 0.56, 95% confidence interval [CI]: 0.34–0.95, p = 0.031). In addition, pathological tumor stage ≥ T3b (HR, 2.12; 95% CI, 1.11–4.02; p = 0.022) and post-salvage PSA nadir ≥ 0.05 ng/ml (HR, 2.54; 95% CI, 1.32–4.90; p = 0.005) were significantly related to salvage treatment failure. Particularly, post-salvage PSA nadir ≥ 0.05 ng/ml was the only predictor of CP (HR, 2.74; 95% CI, 1.23–6.12; p = 0.014). However, there was no significant difference between the groups and none of the factors had a significant effect on OS. Conclusion In the patient with LNP prostate cancer, salvage ADT with RT improved BCR-free survival but did not impact on CP-free survival and OS. PO-1319 Early Health Economic Analysis of 1.5T MRI-guided Radiotherapy for Localized Prostate Cancer C. Hehakaya 1 , J.R. van der Voort van Zyp 1 , B.G. Vanneste 2 , J.P. Grutters 3 , D.E. Grobbee 4 , H.M. Verkooijen 1 , G.W. Frederix 5 1 University Medical Center Utrecht, Imaging & Oncology, Utrecht, The Netherlands; 2 MAASTRO Clinic, Radiation Oncology, Maastricht, The Netherlands; 3 Radboud Institute for Health Sciences, Radboudumc,