ESTRO 38 Abstract book

S454 ESTRO 38

According to the pretreatment PSMA-PET/CT 92 patients (30.2%) had a recurrence in the prostate bed only, 134 (43.9%) had recurrence in the lymphatics with or without prostate bed recurrence and 79 patients (25.9%) had distant metastasis. RT was directed to the PET/CT- positive lesions only, without elective RT in 85 patients (27.9%). The prostate bed was irradiated in 234 patients (76.7%) either electively (103 patients) or because of a PSMA-PET/CT detected recurrence (131 patients). 71 patients (23.3%) received treatment to other lesions without irradiation of the prostate bed. If the prostate bed was electively irradiated the median dose was 66.6 Gy (range, 48 – 70 Gy) in single doses of 1.8 – 2 Gy. If pelvic lymphatics were electively irradiated median dose was 47.5 Gy (range, 42–56 Gy) in single doses of 1.8 Gy (1.5 – 2 Gy). Most patients were treated with conventional RT 155 (50,8%) or conventional RT with a simultaneous integrated boost (SIB) technique 122 (40%). SBRT was used in 18 (5,9%) and combined SBRT and conventional RT in 10 (3,3%) patients. Patients who did not receive elective RT of the prostate bed had a 3- year biochemical free survival of 38% compared to 57% of patients who received RT of the prostate bed. Median biochemical free survival was 24 vs. 32 months (p=0.03). Dose to the prostate bed or lymph nodes had no influence on PFS. Elective RT to the pelvic or paraaortic lymph nodes did not result in a statistically significant difference in PFS (25 vs. 30 months). In multivariate analysis location of recurrence and type of radiotherapy (conventional RT vs. SBRT and combined conventional/SBRT) were significantly associated with PFS. Conclusion Treatment regimens for PSMA-positive oligorecurrent prostate cancer in 6 academic institutions vary substantially in terms of treatment fields and technique. Patients who did not receive elective irradiation of the prostate bed had a significantly worse PFS than patients who received elective irradiation of the prostate bed. PO-0862 P2 RCT of Home-based physical activity in pts treated by ADT and EBRT for localised prostate carcinoma C.P. Doyle 1 , P. Thirion 2 , B. O'Neill 2 , M. Dunne 2 , V. Curtis 3 1 Trinity Biomedical Science Institute, Medicine, Dublin, Ireland ; 2 St Lukes Radiation Oncology Network, Radiation Oncology, Dublin, Ireland ; 3 The London School of Hygiene and Tropical Medicine, Disease Control, London, United Kingdom Purpose or Objective To assess the feasibility and efficacy of a home-based moderate-to-vigorous physical activity walking exercise intervention (MVPA-WEI) in patients (pts) with localised prostate cancer treated by protracted (6-8 weeks) fractionated External Beam Radiotherapy (EBRT) and short-term (< 1 year) Androgen Deprivation (ADT). Material and Methods A Phase 2 randomised trial compared standard of care versus home-based MVPA-WEI, consisting of a prescription of 3000 steps in 30 minutes on 5 days each week, i.e. a cadence of 100 steps/minute (in addition to patient pre- determined habitual step/day) for the duration of radiotherapy (7-8 weeks). Patients treated radically for localised prostate carcinoma by a combination of AD and EBRT, having completed a minimum of 3 month of induction and requiring concomitant AD during EBRT, in addition to having a sedentary life style were eligible for recruitment. Intervention feasibility was evaluated through quantitative and qualitative methods. The efficacy end- points were: Adherence to exercise prescription (pedometer and logbook [walking frequency, intensity and time]), Fatigue (Brief Fatigue Inventory [0-90]), Health Related Quality of Life (FACT-P [0-156]), Anthropometric measures (Weight [kg], % Body fat, % Muscle mass, Waist

volume was 5.91 cc (95% CI 5.49 – 6.34) compared to the reference contour volume of 6.46 cc. The mean DICE similarity coefficient (ideal value 1) for method A was 0.67 (95% CI 0.63 – 0.71), and was significantly higher for method B at 0.81 (95% CI 0.78 – 0.84, p= <0.0001), demonstrating greater concordance with the reference contour. The mean DI (ideal value 0) was 0.35 (95% CI 0.28 – 0.43) for method A, and was significantly lower for method B at 0.15 (95% CI 0.11 – 0.18, p=<0.0001) indicating a lower possibility of excessive contouring with this method, in comparison to the reference contour. The was not a significant difference in mean GMI (ideal value 0), at 0.24 (95% CI 0.16 – 0.32) for method A, and 0.23 for method B (95% CI 0.18 – 0.27, p= 0.7). Conclusion Consistency of pSV delineation is improved by the use of a circumferential prostate margin to define the extent of the seminal vesicles to be included in the target volume. This method is recommended for use in future prostate radiotherapy trials, and will be adapted for the PACE C trial which will compare SBRT with conventional radiotherapy in higher risk patients, including 2cm pSV within the CTV. PO-0861 Analysis of nodal and prostatic bed RT in oligorecurrent PC patients treated with PSMA-PET- guided RT S. Kirste 1 , S. Kroeze 2 , C. Henkenberens 3 , N. Schmidt- Hegemann 4 , M. Vogel 5 , J. Becker 6 , H. Christiansen 7 , S. Combs 8 , A. Müller 9 , C. Belka 10 , M. Guckenberger 2 , A. Grosu 11 1 University Hospital Freiburg, Radiooncology, Freiburg, Germany ; 2 University Hospital Zürich, Department of Radiation Oncology, Zürich, Switzerland ; 3 Medical School Hannover, Department of Radiooncology and Special Oncology, Hannover, Germany ; 4 University Hospital LMU Munich, Department of Radiation Oncology, Munich, Germany ; 5 Technical University Munich, Department of Radiation Oncology, Munich, Germany ; 6 University Hospital Tübingen, Department of Radiooncology, Tübingen, Germany ; 7 Medical School Hannover, Department of Radiotherapy and Special Oncology, Hannover, Germany ; 8 Technical University Munich, Department of Radiooncology, Munich, Germany ; 9 University Hospital Tübingen, Department of Radiation Oncology, Tübingen, Germany ; 10 University Hospital LMU Munich, Department of Radiooncology, Munich, Germany ; 11 University of Freiburg, Department of Radiooncology, Freiburg, Germany Purpose or Objective Patients with prostate cancer and PSMA-PET/CT detected oligo-recurrent disease are a very heterogeneously treated group of patients. Various treatment regimens are currently practiced in different institutions in an individual approach to this patient group; in particular, there are no clear recommendations concerning doses, treatment fields and radiation techniques (conventional versus hypofractionated versus stereotactic body radiotherapy). This study´s aim is to investigate treatment patterns at different institutions and to analyze the influence of target volume concepts on progression-free- survival (PFS). Material and Methods Data of 305 patients from 6 different academic centers that were treated with definite radiotherapy (RT) because of oligorecurrent 68Ga-PSMA -positive prostate cancer between 04/2013 and 01/2018 were evaluated. To describe treatment regimen at different institutions descriptive statistics was used. PFS was analyzed using Kaplan-Meier survival curves and log rank testing. Uni-, and multivariate analyses were performed to determine influence of treatment parameters on PFS. Results