Prostate-specific antigen: concepts for staging prostate cancer and monitoring response to therapy.

FINDINGS: The prostate-specific antigen (PSA) level alone does not facilitate precise pathologic staging on an individual basis, although advanced stage tends to correlate with an increased PSA level. The staging accuracy of PSA, however, can be enhanced by considering the variables of tumor grade and clinical stage. Staging radionuclide bone scans in asymptomatic, untreated patients with clinically localized prostate cancer and a PSA value of less than 10.0 ng/mL are unnecessary. After radical prostatectomy, the serum PSA level is exquisitely sensitive to recurrent or residual disease. Ultrasensitive PSA assays can increase the sensitivity of PSA as a tumor marker after surgical removal of the prostate. Currently, however, the clinical usefulness of PSA concentrations detected in the ultrasensitive range after radical prostatectomy is unknown. Serum PSA values aid in monitoring patients who have received definitive radiation therapy for prostate cancer. Patients in whom the serum PSA level decreases to the reference range have a favorable prognosis. An increasing serum PSA concentration after radiation therapy heralds progressive prostate cancer. The serum PSA level after androgen deprivation therapy (ADT) also has prognostic importance in that a decrease to the normal range predicts a prolonged remission in most patients. Because expression of PSA is under direct hormonal influence, however, ADT can decrease the serum PSA value independent of antitumorigenic activity. Patients who have received ADT must be closely monitored for signs of clinical progression because, in some patients, a serum PSA concentration within the reference range may underestimate actual tumor burden and activity.
CONCLUSION: PSA is the most useful and accurate tumor marker for staging and monitoring prostate cancer after therapy.