The fall and rise of prostate-specific antigen: Kinetics of serum prostate-specific antigen levels after radiation therapy for prostate cancer

✍ Scribed by Gunar K. Zagars; Alan Pollack

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 890 KB
• Volume: 72
• Category: Article
• ISSN: 0008-543X
• DOI: 10.1002/1097-0142(19930801)72:3<832::aid-cncr2820720332>3.0.co;2-6

✦ Synopsis

Background. The serum kinetics of prostate-specific antigen (PSA) after radiation therapy for prostate cancer are not well characterized, and the potential prognostic significance of serum half-lives and of serum doubling times is unclear. This study was designed to address those issues.

Methods. One hundred fifty-four patients with at least four serial PSA determinations who received external-beam radiation therapy alone were analyzed to determine PSA kinetics and to correlate kinetic parameters with outcome. Nonlinear regression techniques were used to estimate PSA half-lives and doubling times.

Results. The PSA data fitted well to exponential models consistent with the hypothesis that PSA kinetics after radiation follow first-order (exponential) kinetics. The mean PSA half-life was 1.9 months (range, 0.5 to 9.2 months). No significant correlation existed between halflife and grade, stage, acid phosphatase level, serum testosterone level, or patient age. A weak correlation between half-life and pretreatment PSA level was observed: patients with low PSA levels tended to have longer half-lives. Half-life did not correlate with disease relapse or with the likelihood of developing a rising PSA profile. PSA doubling time in 37 patients with rising values ranged from 1.6 to 53 months (mean, 12.5 months). Doubling times were significantly longer than half-lives by an average factor of 6.5 and there was no correlation between half-life and subsequent doubling time. Doubling times were longer in low-grade tumors.