ESTRO 2023 - Abstract Book

S1246

Digital Posters

ESTRO 2023

H. Abdel-Aty 1 , L. O'Shea 2 , C. Amos 2 , L.C. Brown 2 , E. Grist 2 , G. Attard 2 , N. Clarke 3 , W. Cross 4 , N. vas As 1 , N. James 1

1 Institute of Cancer Research. The Royal Marsden NHS Foundation Trust, Radiotherapy and Imaging, London, United Kingdom; 2 Institute of Clinical Trials & Methodology, MRC Clinical Trials Unit at UCL , London, United Kingdom; 3 The Christie and Salford Royal NHS Foundation Trusts, Department of Urology, Manchester, United Kingdom; 4 St James University Hospital, Leeds, Department of Urology , Leeds, United Kingdom Purpose or Objective The STAMPEDE trial is a multi-arm multi-stage trial platform testing treatments in hormone-sensitive prostate cancer (HSPC). STAMPEDE2 trial has new comparisons investigating stereotactic ablative body radiotherapy (SABR), 177Lutetium PSMA-617, and Abiraterone + Niraparib. We aim to determine current practice in relation to imaging and treatment, and explore the interest of STAMPEDE investigators to participate in STAMPEDE2. Materials and Methods The survey was developed and circulated to 120 UK STAMPEDE sites in May 2022. Questions on access to SABR, 177Lutetium PSMA-617, choice of systemic therapies and use of novel imaging (PET/CT and Whole-body MRI) were included. Sites were given 3 weeks to complete the survey. Results A total of 64 respondents from 58/120 (48%) sites completed the survey. 55/64 (86%) respondents were interested to participate in the SABR comparison, 44/64 (69%) in the 177Lutetium-PSMA-617 comparison, and 56/64 (87.5%) in the Abiraterone + Niraparib comparison. Access to treatment and novel imaging is summarised in table 1. Treatment n/N % [95% CI] SABR (bone, spine, and nodes) 45/64 70 [58-81] 177Lutetium-PSMA-617 7/64 11 [5-21] Novel imaging PET/CT 62/64 97 [89-99] 18F-PSMA PET/CT 36/62 58 [45-70] 18F-Choline PET/CT 25/62 40 [28-54] 68Ga-PSMA PET/CT 23/62 37 [25-50] Whole-body MRI 24/64 38 [26-50] Table 1. Access to treatment and novel imaging. 45/64 (70%) respondents requested PET/CT for disease uncertainty on conventional imaging, and 39/64 (61%) at disease relapse. 13/64 (20%) respondents requested Whole-body MRI in highly selected patients, and 7/64 (11%) for disease uncertainty on conventional imaging. 38/64 (59%) respondents requested scans at baseline and disease relapse in ‘low volume’ metastatic disease, and 29/64 (45%) requested scans at baseline, best response (corresponding to PSA nadir), and at disease relapse in ‘high volume’ metastatic disease. 54/64 (84%) respondents requested a CT and bone scan for best response assessment. 60/64 (94%) respondents used androgen receptor signalling inhibitors (ARSI), and 46/64 (72%) respondents used docetaxel in addition to androgen deprivation therapy (ADT). 29/64 (45%) respondents would consider docetaxel in addition to ADT and ARSI as part of ‘triple therapy’, if available. 46/64 (72%) respondents commenced ARSI with ADT. Conclusion The STAMPEDE2 trial will open with three investigative treatment arms in the HSPC setting. Currently, there is significant variation in practice across study sites in access and application of novel imaging, and therapeutic combinations at treatment initiation. Despite this, the majority of existing trial centres have expressed an interest to participate in STAMPEDE2.

PO-1535 Hypofractionated post-operative prostate bed radiotherapy: ten-years outcomes

A. Castelluccia 1 , F. Tramacere 1 , T. Proto 1 , A. Sallustio 1 , M. Portaluri 1

1 “A. Perrino" Hospital, Department of Radiotherapy, Brindisi, Italy

Purpose or Objective Hypofractionated postoperative prostate bed radiotherapy was non inferior to conventional fractionated postoperative RT in terms of patient-reported genitourinary (GU) or gastrointestinal (GI) toxicity in recent studies. However, long-term results are poor. The aim of this study is to assess efficacy and safety of hypofractionated RT to prostatic bed during 10 years follow-up, in terms of biochemical control and treatment-related late toxicity. Materials and Methods In this retrospective monocentric study, patients (pts) affected by prostate cancer undergoing radical prostatectomy received postoperative hypofractionated RT to prostatic bed. The prescribed dose was of 65 Gy in 2.5 Gy fractions (25 fractions). Prostate bed irradiation was performed using 3D conformal radiotherapy. Treatment efficacy was assessed using