Prostate-specific antigen control with low-dose adjuvant radiotherapy for high-risk prostate cancer

OBJECTIVES To analyze the prostate-specific antigen (PSA) outcome after low-dose adjuvant RT at a single institution, because the role and optimal dose of external beam radiotherapy (RT) after radical prostatectomy for prostare cancer remain controversial. METHODS We retrospectively identified 65 men who had received low-dose adjuvant RT (median 50 Gy) for microscopically positive margins with an undetectable postoperative PSA from 1990 to 2004. Biochemical failure-free survival was the primary endpoint. Biochemical failure was defined as two consecutive PSA increases to greater than 0.2 ng/mL. RESULTS At a median follow-up of 5 years, 2 men had developed distant metastasis, 2 had local recurrence, and 2 had died (neither attributable to prostate cancer). Biochemical failure had occurred in 7 men (11%). The 5 and 8-year rate of biochemical failure-free survival was 87%. A greater Gleason score (P = 0.04) and seminal vesicle invasion (P = 0.04) predicted significantly for increased biochemical failure on univariate analysis. No single factor was significant on multivariate analysis. Men with a Gleason score of 7 or less had a 5-year biochemical failure-free survival rate of more than 90%. In contrast, those with a Gleason score of 8 or more had a 50% risk of biochemical failure at 5 years. Acute bowel or bladder toxicity (all grade 2 or less) developed in 25%. Two men developed chronic urethral stricture requiring dilation, and 34 (51%) developed surgery-related toxicity that persisted throughout and after RT. CONCLUSIONS Low-dose RT is well tolerated and can potentially provide PSA control in men with Gleason score 7 or less disease with positive surgical margins after radical prostatectomy.