Objectives. To determine whether prostate-specific antigen (PSA) velocity (PSAV), used as a selection criterion for salvage radiotherapy (RT) after radical prostatectomy (RP), predicts the likelihood of response to RT in men with biochemical relapse. Methods. We retrospectively reviewed the records of 48 patients who had undergone salvage RT for biochemical relapse after RP. All men were followed up with serial PSA measurements for a minimum of 6 months from their initial PSA recurrence, and RT was only offered to those patients with a serum PSA level remaining at less than 1.0 ng/mL. The response to RT was defined as maintenance of a PSA level of less than 0.1 ng/mL. The pathologic and clinical parameters, including PSAV, were examined to determine their individual ability to predict the response to RT. Results. Of the 48 patients, 30 had maintained a PSA level of less than 0.1 ng/mL at a median follow-up of 16 months. The PSAV was strongly predictive of the likelihood of a response to salvage RT. The median relapse-free survival time for patients with a PSAV of less than 0.035 ng/mL/mo was 28 months compared with 16 months for patients with a PSAV greater than 0.035 ng/mL/mo. All other parameters tested, including Gleason score, seminal vesicle invasion, extracapsular extension, and margin status, were not predictive of the likelihood of a response to RT. Conclusions. In the present study, PSAV accurately predicted the likelihood of response to salvage RT in men with biochemical relapse after RP. No other pathologic parameters predicted the likelihood of response to RT. Using PSAV as a sole selection criterion for salvage RT after RP may allow improvement in the historically low rates of durable response.
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