Predictor of response to salvage radiotherapy in patients with PSA recurrence after radical prostatectomy: the usefulness of PSA doubling time.

Background: We assessed predictors of response to salvage radiotherapy (sRT) in patients with prostate-specific antigen (PSA) recurrence after radical prostatectomy.
Methods: A total of 21 patients receiving sRT for PSA recurrence without systemic progression after radical prostatectomy had medical records available for retrospective review. We defined sRT as external beam radiotherapy for patients with a continuous increase in PSA level > or =0.2 ng/ml after radical prostatectomy. Response was defined as achievement of a PSA nadir of < or =0.1 ng/ml. Various pre-treatment parameters were evaluated retrospectively.
Results: The median follow-up period after sRT was 38 months. Of the 21 patients, 15 were good responders (71%). The only predictive factor was PSA doubling time (PSADT). Age and PSA level at diagnosis, Gleason score and surgical margin status were not significant predictors of response. The median PSADT in responders was 6.2 months versus 1.9 months in non-responders (P = 0.019). The patients with a PSADT of > or =5 months were all responders.
Conclusion: PSADT appears to be a good predictor of response to sRT. sRT was especially effective when PSADT was > or =5 months.