EFFECT OF HIGHER RADIATION-DOSE ON BIOCHEMICAL CONTROL AFTER RADICAL PROSTATECTOMY FOR PT3N0 PROSTATE-CANCER

Purpose: The appropriate radiation dose has not been determined for po stoperative radiation therapy (RT) of prostate cancer. Postoperative P SA level is a useful marker of local residual disease, and may allow e valuation of RT dose-response after radical prostatectomy. Methods and Materials: Between 1989 and 1996, 86 consecutive patients with pT3N0 prostate cancer who did not receive prior hormonal therapy or chemothe rapy were irradiated postoperatively. All patients received 55.8 to 70 .2 Gy (median = 64.8 Gy) to the prostatic/seminal vesicle bed. Patient s were judged to be free of biochemical failure (bNED) if their PSA re mained undetectable or decreased to undetectable level (< 0.2 ng/ml). The median follow-up time was 32 months from time of irradiation. Resu lts: Univariate and multivariate analyses of variables showed that the preRT PSA level was the most significant predictor of improved bNED s urvival (p < 0.001), Actuarial analyses of radiation dose grouped with preRT PSA levels found higher radiation dose to be significant (p < 0 .05). For the 52 patients with an undetectable preRT PSA level, the 3- year bNED rate was 91% for patients irradiated to 61.5 Gy or more and 57% for those irradiated to lower doses (p = 0.01), For the 21 patient s with preRT PSA level > 0.2 and less than or equal to 2.0 ng/ml, the 3-year bNED rate was 79% for patients irradiated to 64.8 Gy or more an d 33% for those irradiated to a lower dose (p = 0.02), No other preRT PSA interval or radiation dose level was associated with a dose-respon se function. Conclusion: In patients with pT3N0 prostate cancer after radical prostatectomy, a radiation dose-response function may be prese nt and depends on the preRT PSA value. Patients with high postoperativ e PSA levels (> 2.0 ng/ml) may be less likely to benefit from higher d oses of RT, and should be considered a group for which systemic therap y should be tested. (C) 1998 Elsevier Science Inc.