Prostate-specific antigen as a marker of disease activity in prostate cancer.

Despite the impact of prostate-specific antigen (PSA) testing on the detection and management of prostate cancer, controversy about its usefulness as a marker of disease activity continues. This review, based on a recent roundtable discussion, examines whether PSA measurements can be used rationally in several clinical settings. Following radical prostatectomy and radiation therapy, prediction of survival by PSA level is most reliable in high-risk patients. PSA doubling time after radiation therapy is the strongest predictor of biochemical failure. PSA measurements have been associated with inconsistent results following hormonal treatment; reduced PSA levels may result from antiandrogen treatment, which decreases expression of the PSA gene, and therefore, the level of PSA production. In the setting of primary and secondary cancer prevention, PSA is important in risk stratification when selecting patients for studies. Part 1 of this two-part article, which concludes in the September issue, focuses on the physiology of PSA, its measurement and use in clinical practice, and its predictive value following radical prostatectomy and radiation therapy.