Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1172 page)

   Artifactual (e.g., improper specimen collection; very high PSA levels)

   Finasteride (5-α-reductase inhibitor) reduces PSA by 50% after 6 months in men without cancer

   Limitations

   PSA has been recommended by the American Cancer Society for use in conjunction with a DRE for the early detection of prostate cancer starting at age 50 years for men with at least a 10-year life expectancy. Men at high risk, such as those of African descent or with a family history of the disease, may begin testing at an earlier age.

   PSA levels that are measured repeatedly over time may vary both because of imprecision in the analysis and biologic variability where the true PSA level in a given man is different on different measurements. This could potentially lead to an apparent rise in the PSA level, when no actual rise had occurred.

   It is highly recommended that the same assay method be used for longitudinal monitoring.

   A change in PSA of >30% in men with a PSA initially below 2.0 ng/mL was likely to indicate a true change beyond normal random variation.

   The acceptable PSA levels are less clear after radiation therapy, where values may not reach undetectable concentrations. With a nadir of <0.5 ng/mL, relapse is not likely with 5 years of treatment. Biochemical recurrence has been defined by the ASTRO as three consecutive increases in PSA above the nadir.

   The 5-α-reductase inhibitor drugs may affect PSA levels in some patients. Other drugs used to treat benign prostatic hyperplasia may also affect PSA levels. Drugs that decrease PSA levels include buserelin, finasteride, and flutamide. Care should be taken in interpreting results from patients taking these drugs.

   Although screening for prostate cancer with PSA can reduce mortality due to prostate cancer, the absolute risk reduction is small. ACS recommends providing sufficient information regarding risks and benefits of screening and treatment to men to make informed shared decision. For those who decide to screen PSA with or without DRE for average-risk men beginning 50 years of age. Screening should not be offered to men whose life expectancy is <10 years. Men who have >2.5 ng/mL level should undergo annual testing.

   AUA guidelines recommend screening against men younger than 40 years of age and does not recommend routine screening for average-risk men of 40–54 years of age, men older than 70 years, or men whose life expectancy of <10–15 years.

   USPSTF recommend that men not to be screened for prostate cancer. They did advise that men requesting screening be supported in making an informed decision.