Early PSA decrease is an independent predictive factor of clinical failure and specific survival in patients with localized prostate cancer treated by radiotherapy with or without androgen deprivation therapy

Background: The aim was to identify predictors of outcome in patients with localized prostate cancer treated with external beam radiotherapy (EBRT), with or without androgen deprivation therapy (ADT). Materials and methods: A total of 448 patients with prostate cancer received EBRT alone (n = 361, group 1) or ADT followed by EBRT (n = 87, group 2). In group 2, ADT was initiated 3 months before EBRT. After baseline prostatespecific antigen (PSA) determination (PSA_preRT), PSA was assessed during the 6th week of the EBRT course (PSA_6wRT) in group 1. In group 2, PSA was measured again 3 months after the start of ADT, before EBRT (PSA_ADT-preRT). Results: In group 1, median PSA_6wRT/PSA_preRT was 0.72 and median prostate-specific antigen velocity (PSAV) was 21.5 ng/ml/month. In the multivariate analysis, prognostic groups and PSA_6wRT/PSA_preRT (or PSAV) independently predicted biochemical failure (BF), clinical failure (CF), and prostate cancer-specific survival. In group 2, the median PSA_ADT-preRT was 1.3 ng/ml. In the high-risk group, an undetectable PSA_ADT-preRT (≤0.2 ng/ml) predicted BF (P < 0.01) and CF (P = 0.007). Conclusion: A PSA decline 6 weeks after the start of EBRT when used as monotherapy and 3 months after the start of ADT in patients treated with combined ADT and EBRT is predictive of progression and specific survival.