Preirradiation PSA predicts biochemical disease-free survival in patients treated with postprostatectomy external beam irradiation

Purpose: To assess the clinical outcome and prostate-specific antigen (PSA) response and to determine prognostic factors for biochemical disease- free survival in patients treated with external beam radiotherapy following radical prostatectomy without hormonal therapy. Methods and Materials: Forty- eight patients were treated after prostatectomy with radiotherapy between March, 1988 and December, 1993. Seven patients had undetectable PSA (<0.2) and the remainder had detectable PSA at the time of irradiation (overall: median 2.7, range 0-24.9). Nine patients had biopsy proven local recurrence, palpable local disease, or positive preirradiation imaging. No patients received hormonal therapy prior to irradiation. Median follow-up was 55 months. A median dose of 60 Gy (range 58-66) was given to the prostate bed. Survival was analyzed using the life-table method. Actuarial biochemical disease-free survival was the primary endpoint studied. Results: In patients with dectectable PSA, 51% had levels return to undetectable after irradiation. The actuarial 5-year freedom from biochemical failure for all patients was 24%. A significant difference in biochemical disease-free survival was seen for patients irradiated with preirradiation PSA that was undetectable (p < 0.001), or preirradiation PSA that was ≤2.7 (p = 0.002), vs. preirradiation PSA that was >2.7. Five-year actuarial biochemical disease-free survival values were 71, 48, and 0%, respectively, for the three groups. Biochemical disease-free survival was not affected by preoperative PSA level, clinical stage, Gleason's score, pathologic stage, surgical margins, presence of undetectable PSA after surgery, surgery to radiation interval, total dose, or presence of clinically suspicious local disease. Based on digital rectal exam, there were no local failures. Conclusion: Biochemical disease-free survival after postprostatectomy radiation is predicted by the PSA at the time of irradiation. Clinical local control is excellent, but distant failure remains a significant problem in this population. The addition of concomitant systemic therapy should be investigated in patients with PSA >2.7.