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

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.

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.

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.

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.