Clinical Outcomes of Postoperative Radiotherapy Following Radical Prostatectomy in Patients with Localized Prostate Cancer: A Multicenter Retrospective Study (KROG 18-01) of a Korean Population

Purpose: The purpose of this study was to investigate the clinical outcomes of postoperative radiotherapy (PORT) patients who underwent radical prostatectomy for localized prostate cancer. Materials and methods: Localized prostate cancer patients who received PORT after radical prostatectomy between 2001 and 2012 were identified retrospectively in a multi-institutional database. In total, 1,117 patients in 19 institutions were included. Biochemical failure after PORT was defined as prostate-specific antigen (PSA) ≥ nadir+2 after PORT or initiation of androgen deprivation therapy (ADT) for increasing PSA regardless of its value. Results: Ten-year biochemical failure-free survival, clinical failure-free survival, distant metastasisfree survival, overall survival (OS), and cause-specific survival were 60.5%, 76.2%, 84.4%, 91.1%, and 96.6%, respectively, at a median of 84 months after PORT. Pre-PORT PSA ≤ 0.5 ng/ml and Gleason's score ≤ 7 predicted favorable clinical outcomes, with 10-year OS rates of 92.5% and 94.1%, respectively. The 10-year OS rate was 82.7% for patients with a PSA > 1.0 ng/mL and 86.0% for patients with a Gleason score of 8-10. The addition of longterm ADT (≥ 12 months) to PORT improved OS, particularly in those with a Gleason score of 8-10 or ≥ T3b. Conclusion: Clinical outcomes of PORT in a Korean prostate cancer population were very similar to those in Western countries. Lower Gleason score and serum PSA level at the time of PORT were significantly associated with favorable outcomes. Addition of long-term ADT (≥ 12 months) to PORT should be considered, particularly in unfavorable risk patients with Gleason scores of 8-10 or ≥ T3b.ope