Undetectable PSA predicts outcome after salvage radiotherapy for biochemical recurrence following radical...

Salvage radiotherapy (SRT) is a curative treatment option in patients with biochemical recurrence after radical prostatectomy (RP). Undetectable prostate-specific antigen (PSA) < 0.1 ng/mL following SRT predicts biochemical progression-free survival (BPFS). The aim of this large retrospective study was to evaluate whether this effect persists in an extended follow-up of >5 years.

A total of 678 patients treated with SRT for biochemical recurrence after RP were included. Exclusion criteria were lymph node or distant metastases, pre-SRT PSA > 3 ng/mL, and receipt of androgen deprivation therapy (ADT) between RP and SRT. All patients received a median dose of 70.2 (range 59.4-72.0) Gy to the prostatic fossa. The log-rank test (Kaplan-Meier) and Cox regression analysis were used to evaluate the impact of disease- and treatment-related parameters on BPFS, metastasis-free survival (MFS), and overall survival (OS).

Median follow-up after SRT was 5.6 (range 0.1-14.5) years. The 5-year BPFS was 77.8 % in patients with a PSA nadir < 0.1 ng/mL (undetectable) and 16.3 % in the remaining cohort (p < 0.001). Five-year MFS was 95.3 % with undetectable PSA versus 84.0 % with detectable PSA (p < 0.001), and 5-year OS values were 97.5 % and 92.7 % with undetectable versus detectable PSA, respectively (p = 0.04). In multivariate analysis, undetectable PSA was the strongest predictor of BPFS (HR = 0.122; 95 %CI: 0.080-0.187; p < 0.001) and MFS (HR = 0.262; 95 %CI: 0.136-0.594; p < 0.001), but was not significant for OS (HR = 0.615; 95 %CI: 0.298-1.269; p = 0.189).

PSA < 0.1 ng/mL following SRT without ADT is a significant predictor of BPFS and MFS. The results suggest that it might be feasible to withhold ADT in selected patients if they have undetectable PSA after SRT. Prospective studies are warranted to confirm these findings.