The impact of prostate-specific antigen persistence after radical prostatectomy on the efficacy of salvage radiotherapy in patients with primary N0 prostate cancer.

Objective: To test whether salvage radiotherapy (SRT) in patients with lymph node negative (N0) prostate cancer is equally effective with persistent prostate-specific antigen (PSA) and PSA rising from the undetectable range (<0.1 ng/mL) after radical prostatectomy (RP).

Patients And Methods: We assessed post-SRT PSA progression-free survival (PFS) in 555 patients with prostate cancer. The entire cohort was compared with a risk-adjusted subgroup of 112 patient pairs with matching pre-RP PSA level (±10 ng/mL), Gleason score (≤6 vs 7 vs ≥8), and pre-SRT PSA level (±0.5 ng/mL).

Results: The median follow-up was 6.1 years. After RP, PSA was undetectable in 422 and persistent in 133 patients. PSA persistence and a pre-SRT PSA level of ≥0.5 ng/mL reduced Kaplan-Meier rates of PFS significantly. In multivariate analysis of the entire cohort and after risk adjustment, the pre-SRT PSA level but not post-RP PSA persistence was a significant parameter. In the matched cohort's subgroup with early SRT at a PSA level of <0.5 ng/mL, a trend towards a worse outcome with post-RP PSA persistence was observed. Delayed SRT with a PSA level ≥0.5 ng/mL led to a PFS of <30%, irrespective of the post-RP PSA level.

Conclusion: In patients with N0 prostate cancer with post-RP PSA persistence, early SRT at a PSA level <0.5 ng/mL seems to be less effective than in recurrent patients with post-RP undetectable PSA. They might benefit from intensified therapy, but larger case numbers are required to substantiate this conclusion. In patients with a PSA level ≥0.5 ng/mL and higher-risk features associated with post-RP PSA persistence, SRT alone is unlikely to provide long-term freedom from further progression.