ESTRO 2023 - Abstract Book

S335

Sunday 14 May 2023

ESTRO 2023

1 Nantes Université, Radiation Oncology, NANTES, France; 2 Institut de Cancérologie de l'Ouest, Radiation Oncology, NANTES, France; 3 Centre Oscar Lambret, Radiation Oncology, Lille, France; 4 Hôpital privé du confluent, Radiation Oncology, Nantes, France; 5 CHU St Etienne, Radiation Oncology, St Etienne, France; 6 Institut de Cancérologie de Lorraine, Radiation Oncology, Nancy, France; 7 Institut Bergonié, Radiation Oncology, Bordeaux, France; 8 Centre GF Leclerc, Radiation Oncology, Dijon, France; 9 Centre Léon Bérard, Radiation Oncology, Lyon, France; 10 Centre Jean Perrin, Radiation Oncology, Clermont-Ferrand, France; 11 Clinique Pasteur, Radiation Oncology, Brest, France; 12 Clinique Pasteur, Radiation Oncology, Toulouse, France; 13 Centre François Baclesse, Radiation Oncology, Caen, France; 14 Centre Jean Bernard, Radiation Oncology, Le Mans, France; 15 CHU Créteil, Radiation Oncology, Créteil, France; 16 Institut de Cancérologie de l'Ouest, Nuclear oncology, Nantes, France; 17 Institut de Cancérologie de l'Ouest, Biostatistics, NANTES, France; 18 Institut de cancérologie de l'Ouest, Biostatistics, Nantes, France; 19 Institut de Cancérologie de l'Ouest, Biostatistics, Nantes, France Purpose or Objective The regional salvage treatments of oligorecurrent pelvic nodal relapses in prostatic cancer are debated. Androgen depriving therapy (ADT) is a mainstay in metastatic prostate cancer, and salvage SBRT may offer prolonged complete remission for patients harboring regional nodal relapses. Our objective was to assess the efficacy of the combination of ADT and salvage radiotherapy in men with oligorecurrent pelvic node relapses of prostate cancer. Materials and Methods We conducted an open-label, phase II trial of combined high-dose intensity-modulated radiotherapy (54 Gy in 30 f to the pelvic lymphnodes 66 Gy 30 f to the oligorecurrent pelvic lymphnodes +/- prostate bed irradiation 66 Gy 33f) and ADT (6 months) in oligorecurrent (<6) pelvic node relapses in prostate cancer, detected by fluorocholine PET-CT imaging (OLIGOPELVIS GETUG P07, NCT 02274779). The primary endpoint was 2-yr progression-free survival defined as two consecutive prostate-specific antigen levels above the level at inclusion and/or clinical evidence of progression as per RECIST 1.1 and/or death from any cause. Early toxicity and 2-yr efficacy results were previously reported. Herein we present long-term (5-yr) results. Results We analyzed 67 patients (median age 67.7; 54% had received prior prostatic irradiation). Grade 2 + 5-year genito-urinary and gastrointestinal toxicities were 12% and 3%, respectively. Toxicity was comparable between patients with or without a prior history of prostatic irradiation. Five-year progression-free survival, biochemical relapse–free survival, ADT-free survival and overall survival rates were 38.2%, 30.7%, 58.0% and 90.9%, respectively. In multivariate analysis, prior prostatic irradiation was a strong predictor of relapse (HR=0.38, p<0.01). The site of relapses were local (10.5%), N1 (28.5%), M1a (45%), M1b (18%) and M1c (6%). Conclusion Combined high-dose salvage elective pelvic radiotherapy and 6-month ADT appeared to prolong tumor control in oligorecurrent pelvic node relapses in prostate cancer with limited toxicity. The site of most relapses following salvage pelvic irradiation is paraortic lymphnodes. After 5 years, 31% of patients were still in complete remission. A randomized trial comparing ADT alone vs ADT + RT is ongoing to confirm these results (Oligopelvis 2 GETUG P12 NCT03630666). OC-0435 Multi-institutional nomogram for PSMA-PET based salvage radiotherapy in recurrent prostate cancer C. Zamboglou 1 , K. Ferentinos 2 , A. Arnoux 3 , A. Janbain 3 , I. Strouthose 2 , A. Farolfi 4 , S. A. Koerber 5 , J. C. Peeken 6 , M. Vogel 6 , A. Vrachimis 7 , S. K. B. Spohn 8 , M. Shelan 9 , A. Grosu 10 , S. Kroeze 11 , M. Guckenberger 12 , S.F. Fanti 4 , C. Belka 13 , G. Hruby 14 , S. Scharl 15 , T. Wiegel 15 , C. Henkenberens 16 , L. Emmett 17 , N.S. Schmidt-Hegemann 13 1 University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, Department of Radiation Oncology, Medical Center, Freiburg, Germany; 2 University Hospital of the European University, Limassol, Cyprus, Department of Radiation Oncology, German Oncology Center, Limassol, Cyprus; 3 European Hospital Georges-Pompidou, AP-HP Centre – Paris Cite University, Clinical research unit, Paris , France; 4 IRCCS Azienda Ospedaliero-Universitaria di Bologna, Division of Nuclear Medicine, Bologna, Italy; 5 Heidelberg University Hospital, Department of Radiation Oncology, Heidelberg, Germany; 6 Klinikum rechts der Isar, Technical University of Munich (TUM), Germany, Department of Radiation Oncology, Munich , Germany; 7 University Hospital of the European University, Department of Nuclear Medicine, German Oncology Center, Limassol, Cyprus; 8 University of Freiburg, Faculty of Medicine, Department of Radiation Oncology, Medical Center, Freiburg, Germany; 9 Inselspital Bern, University of Bern, Department of Radiation Oncology, Bern, Switzerland; 10 University of Freiburg, Faculty of Medicine, University of Freiburg, Department of Radiation Oncology, Medical Center, Freiburg, Germany; 11 University of Sydney, Department of Radiation Oncology, Royal North Shore Hospital , Sydney, Australia; 12 University of Sydney, Department of Radiation Oncology, Royal North Shore Hospital, Sydney, Australia; 13 University Hospital, LMU Munich, Department of Radiation Oncology, Munich, Germany; 14 Royal North Shore Hospital – University of Sydney, Australia, Department of Radiation Oncology, Sydney, Australia; 15 University of Ulm, Ulm, Germany, Department of Radiation Oncology, Ulm, Germany; 16 Medical School Hannover, Department of Radiotherapy and Special Oncology, Hannover, Germany; 17 St Vincent’s Hospital Sydney Australia, Department of Theranostics and Nuclear medicine, Sydney , Australia Purpose or Objective We aimed to develop and to validate a multi-institutional nomogram of outcomes for PSMA-PET based salvage radiotherapy (sRT) following radical prostatectomy (RP) for patients with recurrent or persistent prostate cancer (PCa). Materials and Methods Data from patients with a detectable post-RP prostate-specific antigen (PSA) treated with sRT with or without concurrent androgen-deprivation therapy (ADT) were obtained from 11 academic institutions from 5 countries. All patients had a PSMA- PET scan prior sRT and patients with distant metastases on PET were excluded from this analysis. The freedom from biochemical failure (FFBF) rate was estimated, and a predictive nomogram was generated and internally as well as externally validated. For external validation the center with the less homogeneity with the other centers was chosen. Biochemical relapse (BR) was defined as PSA nadir +0.2 ng/ml after sRT.

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