Prostate-specific antigen kinetics after I125-brachytherapy for prostate adenocarcinoma

To investigate a potential correlation between the achievement of a cut-off of nadir PSA (nPSA) after brachytherapy (BRT) with biochemical Disease-Free Survival (bDFS) and to define the rate of post-BRT PSA bounces.

Retrospective analysis was carried out in 105 consecutive patients affected with early-stage prostate adenocarcinoma who underwent (125)I BRT. Only patients with a minimum follow-up ≥24 months were included. Biochemical DFS was chosen as primary endpoint.

At a median follow-up of 51.2 months, 3- and 5-year bDFS were 96.8 and 91.2%, respectively. Median time to biochemical failure (BF) was 54 months. By Kaplan-Meier analysis, patients achieving nPSA ≤ 0.35 ng/mL had significantly higher bDFS (3- and 5-year bDFS: 100 and 98.5 % vs. 83.3 and 66.7 %, respectively; p = 0.001). Bounce PSA occurred in 28.6% of patients, at a median time of 21.5 months. No BFs were observed in the bounce group. Achieving a nPSA ≤ 0.35 ng/mL was the only factor independently associated with long-term bDFS on both univariate (p = 0.000) and multivariate analysis (HR 3.82; p = 0.003).

Patients attaining a nPSA ≤ 0.35 ng/mL are significantly more likely to experience long-term freedom-from-biochemical failure. Bounce PSA occurs in approximately 30% of patients. Time to onset of PSA increase seems the most reliable feature to distinguish bounce from failure. Tailored follow-up strategies are needed for patients at higher risk of recurrence, and caution is advised in interpreting an early increase in PSA levels in the first 24-30 months after BRT.