Significance of early prostate-specific antigen values after salvage radiotherapy in recurrent prostate cancer patients treated with surgery.

OBJECTIVES: To assess the use of post-salvage radiotherapy prostate-specific antigen for early prediction of biochemical failure or clinical recurrence after salvage radiotherapy in recurrent prostate cancer patients after prostatectomy. METHODS: From 2000 to 2011, 164 patients were treated with salvage radiotherapy alone for recurrent prostate cancer. Patients who received androgen deprivation therapy before or within 1 month of the termination of salvage radiotherapy were excluded. Survival analysis was carried out with: (i) a selected prostate-specific antigen reference value (0.2 ng/mL) at the second follow-up period (4 months) after salvage radiotherapy (prostate-specific antigen value over 0.2 ng/mL at post-salvage radiotherapy 4 months); and (ii) prostate-specific antigen percent decline (post-salvage radiotherapy 4 months prostate-specific antigen/pre-salvage radiotherapy prostate-specific antigen). RESULTS: The median follow-up time was 53.4 months (range 8.5-134.1 months). The 5-year clinical recurrence-free survival was 87.9%. Prostate-specific antigen percent decline of 0.45 was set as the cut-off value for clinical recurrence-free survival based on the receiver operating characteristics curve. In the multivariate analysis, a prostate-specific antigen value over 0.2 ng/mL at post-salvage radiotherapy 4 months (P = 0.013) and prostate-specific antigen percent decline ≥ 0.45 (P = 0.002) were both significant parameters predicting clinical recurrence-free survival. Otherwise, prostate-specific antigen percent decline ≥ 0.45 was the only statistically significant predictor of biochemical failure-free survival (biochemical failure-free survival after salvage radiotherapy). CONCLUSIONS: A prostate-specific antigen value over 0.2 ng/mL at post-salvage radiotherapy 4 months and prostate-specific antigen percent decline ≥ 0.45 are negative predictors of clinical recurrence-free survival after salvage radiotherapy. Prostate-specific antigen percent decline ≥ 0.45 is also associated with worse biochemical failure-free survival after salvage radiotherapy. Patients with delayed prostate-specific antigen decrease should be carefully observed for clinical recurrence.