PSA bounce: understanding temporal fluctuations in prostate cancer after external radiotherapy

Purpose: Prostate-specific antigen (PSA) bounce is a transient elevation in PSA levels commonly observed after radiotherapy. This study aims to investigate the characteristics, timing, and clinical implications of PSA bounce (PSA-B) in prostate cancer patients treated with external beam radiotherapy (EBRT), exploring potential causes and its relevance in patient management.

Materials and methods: Between 2013 and 2019, 629 patients with localized prostate cancer were treated with EBRT. After excluding patients with fewer than four PSA measurements or follow-up under 3 years (n = 184), 445 patients were analyzed. The median follow-up duration was 5.9 years (36-105 months). PSA-B was defined as a rise of ≥ 0.2 ng/mL above the nadir, followed by a subsequent decline to or below the nadir. PSA relapse was defined according to Phoenix definition.

Results: A total of 64 patients (14.4%) experienced PSA-B at a median of 31 months (6-68 months). Univariable analysis identified age (p < 0.001), risk group (p < 0.001), perineural invasion (p < 0.007), radiotherapy duration (p < 0.001), and the absence of concurrent hormonal therapy (p < 0.001) as independent predictors of PSA-B. Multivariable analysis confirmed age and high-risk group as significant factors. PSA relapse occurred in 10.3% of cases, with only one patient who experienced both PSA-B and relapse.

Conclusions: PSA-B is a common phenomenon in localized prostate cancer patients post-EBRT. Factors such as age, risk group, perineural invasion, radiotherapy duration, and hormonal treatment use are associated with PSA-B occurrence. Understanding its mechanisms is crucial for optimizing prostate cancer management.