ESTRO 2022 - Abstract Book

S528

Abstract book

ESTRO 2022

OC-0603 PEACE V – STORM randomized phase II trial for oligorecurrent nodal prostate cancer: acute toxicity

T. Zilli 1 , S. Siva 2 , R. Heikkilä 3 , P. Dirix 4 , N. Liefhooghe 5 , F. Otte 6 , A. Gomez-Iturriaga 7 , W. Everaerts 8 , M. Shelan 9 , A. Conde- Moreno 10 , F. López Campos 11 , A. Papachristofilou 12 , M. Guckenberger 13 , M. Scorsetti 14 , A. Zapatero 15 , A. Villafranca Iturre 16 , C. Eito 17 , F. Couñago 18 , P. Muto 19 , L. Van De Voorde 20 , V. Fonteyne 21 , D. Moon 22 , K. Thon 3 , C. Mercier 4 , V. Achard 1 , K. Stellamans 23 , E. Goetghebeur 24 , D. Reynders 24 , P. Ost 25 1 Geneva University Hospital, University of Geneva, Radiation Oncology, Geneva, Switzerland; 2 Epworth Healthcare and Sir Peter MacCallum, University of Melbourne, Department of Oncology, Melbourne, Australia; 3 Oslo University Hospital, Radiation Oncology, Oslo, Norway; 4 Iridium netwerk, GZA Ziekenhuizen, Radiation Oncology, Antwerp, Belgium; 5 AZ Groeninge, Kortrijk, Radiation Oncology, Kortrijk, Belgium; 6 Jules Bordet Institute, Radiation Oncology, Brussels, Belgium; 7 Hospital Universitario Cruces, Radiation oncology, Barakaldo, Spain; 8 University Hospitals Leuven, Urology, Leuven, Belgium; 9 Inselspital, Bern University Hospital, University of Bern, Radiation Oncology, Bern, Switzerland; 10 Hospital Universitari i Politècnic la Fe, Radiation Oncology, Valencia, Spain; 11 Hospital Universitario Ramón y Cajal, Radiation Oncology, Madrid, Spain; 12 University Hospital Basel, Radiation Oncology, Basel, Switzerland; 13 University Hospital Zurich, University of Zurich, Radiation Oncology, Zürich, Switzerland; 14 Humanitas University, Pieve Emanuele (Milan) -IRCCS Humanitas Research Hospital, Radiotherapy and Radiosurgery Department, Rozzano, Italy; 15 University Hospital La Princesa, Radiation Oncology, Madrid, Spain; 16 Complejo Hospitalario de Navarra, Radiation Oncology, Navarra, Spain; 17 Instituto Oncólogico Clinica Universitaria IMQ, Radiation Oncology, Bilbao, Spain; 18 University Hospital Quironsalud, Universidad Europea de Madrid, Radiation Oncology, Madrid, Spain; 19 Napoli Istituto Nazionale Tumori IRCCS Fondazione Pascale, Radiation Oncology, Napoli, Italy; 20 AZ St-Lucas Ghent, Radiation Oncology, Ghent, Belgium; 21 Department of Human Structure and Repair, Ghent University, Radiation Oncology, Ghent, Belgium; 22 University of Melbourne, (Royal Melbourne clinical school), Urology, Melbourne, Australia; 23 AZ Groeninge, Radiation Oncology, Kortrijk, Belgium; 24 Ghent University, Department of Applied Mathematics, Computer Science and Statistics, Ghent, Belgium; 25 Department of Human structure and repair, Ghent University, Radiation Oncology, Ghent, Belgium Purpose or Objective Pelvic nodal recurrences are being increasingly diagnosed in prostate cancer (PCa) patients with the introduction of new molecular imaging techniques, like choline and PSMA PET-CT. At this moment, there are no specific treatment recommendations for patients with limited nodal recurrences and different locoregional treatment approaches are currently being used. The aim of this prospective multicentre randomized controlled phase II trial is to compare metastasis directed therapy (MDT) with elective nodal pelvic radiotherapy (ENRT). Materials and Methods STORM is an international, phase II, open-label, randomised, superiority trial. Patients diagnosed with PET-detected pelvic nodal oligorecurrence ( ≤ 5 nodes) following radical local treatment for PCa, were randomized in a 1:1 ratio between arm A: MDT and 6 months of androgen deprivation therapy (ADT), or arm B: ENRT (25x1.8Gy) with MDT and 6 months of ADT. Patients were stratified by type of PET-tracer (choline or PSMA) and by type of MDT (surgery or radiotherapy). In case of radiotherapy, SBRT (3x10Gy) was used for arm A, with a simultaneous integrated boost (25x2.6Gy) in arm B. The primary endpoint is metastasis-free survival and here we report the secondary endpoint acute toxicity, defined as worst grade 2 or more CTCAEv4.0 gastrointestinal (GI) or genitourinary (GU) toxicity, exceeding baseline, up to 3 months after radiotherapy. The chi-square test was used to compare toxicity between treatment arms. This study is registered on ClinicalTrials.gov Identifier: NCT03569241 Results Between June, 2018 and April 2021, 196 patients were randomly assigned to MDT or ENRT. 96 of 98 allocated to MDT and 93 of 98 patients allocated to ENRT received at least one fraction of the allocated treatment. Initial treatment at diagnosis was radical prostatectomy in 166 patients (88%) with lymph node dissection in 96 patients (49%). At time of nodal recurrence, the median PSA was 0.97 ng/ml (interquartile range 0.45-2.3). The PET-tracer was choline in 32 (17%) patients and PSMA in 157 (83%) patients. Patients were diagnosed with a single node, 2 nodes or 3-5 nodes in 110 (58%), 49 (26%), 28 (15%) patients (missing information for 2 patients). Surgery was the MDT type of choice in only 11 patients (6%). GI and GU toxicity at baseline, month 1 and month 3 are displayed in figure 1. Worst acute GI toxicity proportions were as follows: grade 2 or higher events in 1 (1%) in the MDT group versus 3 (3%) in the ENRT group (p=0.13). Worst acute GU toxicity proportions were as follows: grade 2 or higher events in 8 (8%) in the MDT group versus 13 (13%) in the ENRT group (p=0.54). Two patients developed a grade 3 event (diarrhoea and urinary incontinence with pre-existing grade 2) in the ENRT arm. Conclusion Although ENRT treats a more extensive part of the pelvis as compared to MDT, ENRT does not seem to result in a clinically meaningful increase in acute GI or GU toxicity.