Prostate-specific antigen (PSA) nadir and experience of PSA bounce after low-dose-rate brachytherapy for prostate cancer predicts clinical failure.

Objective: This study aimed to assess if prostate-specific antigen (PSA) threshold and PSA bounce are associated with oncological control after low-dose-rate brachytherapy (LDR-BT) alone or with external beam radiotherapy (EBRT), with or without androgen deprivation therapy (ADT), considering serum testosterone levels.

Methods: This study enrolled 944 prostate cancer patients treated at a single institution with LDR-BT alone or LDR-BT combined with EBRT, with or without ADT. The Fine-Gray hazard model was used to evaluate factors related to clinical failure, including experience of PSA bounce between baseline and 2, 4, or 7 years after LDR-BT and PSA value (0.1, 0.2, or 0.5 ng/mL) with normal testosterone levels at 2, 4, and 7 years after LDR-BT, respectively.

Results: Patients with normal testosterone levels and a PSA of 0.2 or 0.5 ng/mL at 2, 4, and 7 years after LDR-BT had a significantly better clinical failure free rate (CFFR) than those with PSA levels >0.2 or >0.5 ng/mL or low testosterone levels. Multivariate analysis revealed that PSA <0.1, 0.2, or 0.5 ng/mL with normal testosterone levels at 2, 4, and 7 years and experience of PSA bounce between baseline and 2 or 4 years after LDR-BT were significantly related to better CFFR.

Conclusions: Patients with normal serum testosterone levels who reached PSA of <0.1, 0.2, or 0.5 ng/mL after LDR-BT, or those who experienced PSA bounce, showed better oncological control.