Prostate-specific antigen 'bounce' after permanent ¹²⁵I-implant brachytherapy in Japanese men: A multi-institutional pooled analysis

Objective To examine the incidence, timing, and magnitude of the prostate-specific antigen (PSA) level 'bounce' after permanent prostate brachytherapy (BT) and correlate the PSA bounce with clinical and dosimetric factors in Japanese patients with prostate cancer. Patients and methods A multi-institutional pooled analysis was carried out in 388 consecutive patients with T1-T2N0M0 prostate cancer treated with ¹²⁵I-seed implant BT with no hormonal therapy or external beam radiotherapy. All patients had ≥1 year of follow-up and at least three follow-up PSA level measurements. Three definitions of PSA bounce were used: definition A, a PSA level rise of 0.1 ng/mL; definition B, a PSA level rise of 0.4 ng/mL; and definition C, a PSA level rise of 35% over the previous value, followed by a subsequent fall. RESULTS The actuarial likelihood of having PSA bounce at 24 months was 50.8% for definition A, 23.5% for definition B, and 19.4% for definition C. The median time to develop PSA bounce was 12 months for definition A, 18 months for definition B, and 18 months for definition C. There was a PSA bounce magnitude of 2 ng/mL in 5.3% of patients, and 95.3% of PSA bounce occurred within 24 months after ¹²⁵I-BT. Among the before and after ¹²⁵I-BT factors, clinical stage, initial PSA level, and Gleason score did not predict for PSA bounce using any definition; only being younger predicted for PSA bounce on multivariate analysis (P < 0.001). CONCLUSIONS PSA bounce is a common phenomenon after ¹²⁵I-BT and occurred at a rate of 19-51% in the Japanese men who underwent ¹²⁵I-BT, depending on the definition used. It is more common in younger patients, and early PSA bounce should be considered when assessing a patient with a rising PSA level after ¹²⁵I-BT, before implementing salvage interventions. Furthermore, PSA bounce magnitude might be lower in Japanese than in Caucasian patients.