ESTRO 2023

Session Item

Sunday

May 14

10:30 - 11:30

Plenary Hall

Genito-urinary

Chair: Daniel Matthias Aebersold, Switzerland;

Co-Chair: Johannes Knoth, Austria

Session Type: Proffered Papers

Track: Clinical

Journey:

11:10 - 11:20

Multi-institutional nomogram for PSMA-PET based salvage radiotherapy in recurrent prostate cancer

Constantinos Zamboglou, Cyprus

Presentation Number: OC-0435

Abstract

Abstract Title:

Multi-institutional nomogram for PSMA-PET based salvage radiotherapy in recurrent prostate cancer

Authors:

Constantinos Zamboglou¹, Konstantinos Ferentinos², Armelle Arnoux³, Ali Janbain³, Iosif Strouthose², Andrea Farolfi⁴, Stefan A. Koerber⁵, Jan C. Peeken⁶, Marco Vogel⁶, Alexis Vrachimis⁷, Simon K. B. Spohn⁸, Mohamed Shelan⁹, Anca-Ligia Grosu¹⁰, Stephanie Kroeze¹¹, Matthias Guckenberger¹², Stefano Fanti Fanti⁴, Claus Belka¹³, George Hruby¹⁴, S. Scharl¹⁵, Thomas Wiegel¹⁵, Christoph Henkenberens¹⁶, Louise Emmett¹⁷, Nina Sophie Schmidt-Hegemann¹³

¹University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, Department of Radiation Oncology, Medical Center, Freiburg, Germany; ²University Hospital of the European University, Limassol, Cyprus, Department of Radiation Oncology, German Oncology Center, Limassol, Cyprus; ³European Hospital Georges-Pompidou, AP-HP Centre – Paris Cite University, Clinical research unit, Paris , France; ⁴IRCCS Azienda Ospedaliero-Universitaria di Bologna, Division of Nuclear Medicine, Bologna, Italy; ⁵Heidelberg University Hospital, Department of Radiation Oncology, Heidelberg, Germany; ⁶Klinikum 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; ⁸University of Freiburg, Faculty of Medicine, Department of Radiation Oncology, Medical Center, Freiburg, Germany; ⁹Inselspital Bern, University of Bern, Department of Radiation Oncology, Bern, Switzerland; ¹⁰University of Freiburg, Faculty of Medicine, University of Freiburg, Department of Radiation Oncology, Medical Center, Freiburg, Germany; ¹¹University of Sydney, Department of Radiation Oncology, Royal North Shore Hospital , Sydney, Australia; ¹²University of Sydney, Department of Radiation Oncology, Royal North Shore Hospital, Sydney, Australia; ¹³University Hospital, LMU Munich, Department of Radiation Oncology, Munich, Germany; ¹⁴Royal North Shore Hospital – University of Sydney, Australia, Department of Radiation Oncology, Sydney, Australia; ¹⁵University of Ulm, Ulm, Germany, Department of Radiation Oncology, Ulm, Germany; ¹⁶Medical School Hannover, Department of Radiotherapy and Special Oncology, Hannover, Germany; ¹⁷St Vincent’s Hospital Sydney Australia, Department of Theranostics and Nuclear medicine, Sydney , Australia

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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).

Material 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.

Results

Overall, 1029 patients (training set n=798, internal and external validation set n=271 and 50) with a median follow-up of 33 months were included. On PSMA-PET, 427 (42%) and 313 (30%) patients had local and nodal recurrences, respectively. Elective pelvic lymphatics were irradiated in 368 (36%) patients. All patients received sRT to the prostatic fossa receiving a dose of <66 Gy, 66-70 Gy and >70 Gy in 103 (10%), 551 (54%) and 375 (36%) patients, respectively. Androgen deprivation therapy (ADT) was given in 325 (32%) patients. On multivariable Cox regression analysis, pre-SRT PSA, ISUP grade, pT stage, surgical margins, ADT use, sRT dose and nodal recurrence on PSMA PET were significantly associated with FFBF. The nomogram concordance index was 0.72 and 0.67 for FFBF in internal and external validation, respectively.

Conclusion

We present a validated contemporary nomogram which can estimate individual patient outcomes after PSMA-PET guided sRT. Positive lymph nodes on PSMA-PET seem to be a new risk factor for BR after sRT.