Prognostic risk classification for biochemical relapse-free survival in patients with oligorecurrent prostate cancer after [68Ga]PSMA-PET-guided metastasis-directed therapy.

Since the success of prostate-specific membrane antigen-positron emission tomography (PSMA-PET) imaging for patients with oligorecurrent prostate cancer (ORPC), it is increasingly used for radiotherapy as metastasis-directed therapy (MDT). Therefore, we developed a prognostic risk classification for biochemical relapse-free survival (bRFS) for patients after PSMA-PET-guided MDT after radical prostatectomy.

We analyzed 292 patients with local recurrence (LR) and/or pelvic lymph node (LN) lesions and/or up to five distant LN, bone (BM), or visceral metastases (VM) detected with [68Ga]PSMA-PET imaging. Median follow-up was 16 months (range 0-57). The primary endpoint was bRFS after MDT. Cox regression analysis for risk factors was incorporated into a recursive partitioning analysis (RPA) with classification and regression tree method.

PSA at recurrence ≥ 0.8 ng/mL, BM, and VM was significantly associated with biochemical relapse. RPA showed five groups with tenfold cross-validation of 0.294 (SE 0.032). After building risk classes I to IV (p < 0.0001), mean bRFS was 36.3 months (95% CI 32.4-40.1) in class I (PSA < 0.8 ng/mL, no BM) and 25.8 months (95% CI 22.5-29.1) in class II (PSA ≥ 0.8 ng/mL, no BM, no VM). LR and/or pelvic LNs caused relapse in classes I and II. Mean bRFS was 16.0 months (95% CI 12.4-19.6) in class III (PSA irrelevant, present BM) and 5.7 months (95% CI 2.7-8.7) in class IV (PSA ≥ 0.8 ng/mL, no BM, present VM).

We developed and internally validated a risk classification for bRFS after PSMA-PET-guided MDT. Patients with PSA < 0.8 ng/mL and local relapse only (LR and/or pelvic LNs) had the most promising bRFS. PSA ≥ 0.8 ng/mL and local relapse only (LR and/or pelvic LNs) indicated intermediate risk for failure. Patients with BM were at higher risk regardless of the PSA. However, those patients still show satisfactory bRFS. In patients with VM, bRFS is heavily decreased. MDT in such cases should be discussed individually.

European journal of nuclear medicine and molecular imaging. 2020 Mar 16 [Epub ahead of print]

Marco M E Vogel, Stephanie G C Kroeze, Christoph Henkenberens, Nina-Sophie Schmidt-Hegemann, Simon Kirste, Jessica Becker, Irene A Burger, Thorsten Derlin, Peter Bartenstein, Michael Mix, Christian la Fougère, Matthias Eiber, Hans Christiansen, Claus Belka, Anca L Grosu, Arndt-Christian Müller, Matthias Guckenberger, Stephanie E Combs

Department of Radiation Oncology, Klinikum rechts der Isar, Technical University of Munich (TUM), Ismaninger Strasse 22, 81675, Munich, Germany. ., Department of Radiation Oncology, University Hospital Zurich, University of Zurich, Zurich, Switzerland., Department of Radiotherapy and Special Oncology, Medical School Hannover, Hannover, Germany., Department of Radiation Oncology, University Hospital LMU Munich, Munich, Germany., Department of Radiation Oncology, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany., Department of Radiation Oncology, University Hospital Tübingen, Eberhard Karls University Tübingen, Tübingen, Germany., Department of Nuclear Medicine, University Hospital Zurich, University of Zurich, Zurich, Switzerland., Department of Nuclear Medicine, Hannover Medical School, Hannover, Germany., Department of Nuclear Medicine, University Hospital LMU Munich, Munich, Germany., Department of Nuclear Medicine, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany., Department of Nuclear Medicine and Clinical Molecular Imaging, University Hospital Tübingen, Eberhard Karls University Tübingen, Tübingen, Germany., Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich (TUM), Munich, Germany., Department of Radiation Oncology, Klinikum rechts der Isar, Technical University of Munich (TUM), Ismaninger Strasse 22, 81675, Munich, Germany.