Incidence and prognostic implications of PSA relapse after radical radiotherapy for prostate cancer: a population-based study.

[OBJECTIVE] To estimate risk of prostate-specific antigen (PSA) relapse after radical radiotherapy (RT) for prostate cancer (PCa), and risk of PCa death after relapse according to Gleason score and time to relapse.

[PATIENTS AND METHODS] Men in the National Prostate Cancer Register of Sweden who underwent primary radical RT in 2007-2024 were followed until 31 December 2024. Relapse was defined as a PSA level increase of ≥2 ng/mL above nadir (Phoenix criteria). Competing risk cumulative incidence analyses were used to estimate risk of PSA relapse and risk of PCa death after relapse according to Gleason score and time to relapse.

[RESULTS] The 10-year risk of relapse in 26 634 men treated with RT was 25% (95% confidence interval [CI] 24-25%). The 10-year risk of PCa death after relapse was 35% (95% CI 33-37%). In men with relapse after >3 years the risk was 18% for Gleason score 6 and 19% for Gleason score 3 + 4, while in men with a relapse within 18 months the risk was 52% for Gleason score 4 + 3 and 75% for Gleason score 9-10. In men with a relapse at 1 year after RT there was a four-fold higher risk of PCa death for men with Gleason score 9-10 compared to men with Gleason score 6 (86% vs 22%). In contrast, in men with a relapse at 10 years after RT there were little differences in risk of PCa death according to Gleason (14% vs 23%).

[CONCLUSION] In this population-based study of RT for PCa, there was a wide range in the estimates of risk of PCa death after relapse in highly granular groups according to Gleason score and time to relapse. Notably, some estimates did not align with the European Association of Urology relapse risk group classification.