Prostate cancer is the most common cancer in men and the third leading cause of cancer in the European Union. Men with a family history of prostate cancer are advised to start screening at the age of 40-45, whilst others are advised after 50. Screening for the cancer involves detection of Prostate Specific Antigen (PSA), which is a protein produced exclusively by the prostate and released into the blood in small quantities. Normal PSA levels are considered to be 4 ng/mL whilst levels greater than 10 ng/mL indicate a high risk for prostate cancer.

In the 1980s, PSA was approved as a test to help manage patients diagnosed with prostate cancer, and later was approved as a diagnostic tool. The testing allows for early detection of a disease that is so often undiagnosed due to its symptomless progression. Interpretation of the PSA tests can be complicated and cut-off values differ between laboratories. PSA levels change over time depending on the size of the tumour and how fast it grows. For non-aggressive cancers “watching-waiting” can be employed, whereby PSA levels are tested every 6-12 months and an increase in PSA levels is indicative of disease progression. Surgical removal of the prostate will result in a decrease in PSA levels. Unless of course, the gland isn’t completely removed, the cancer has recurred or indeed metastasized. 

However, increases in PSA levels don’t always mean prostate cancer, and the PSA test can frequently give false positive reads. Since its introduction as a screening tool, PSA testing has led to the discovery of non-fatal cancers, or those, which would not have been detected in the absence of screening, which has led to over-diagnosis. This has inevitably led to over-treatment. And as no man would choose to live with an unpredictable cancer (whether falsely diagnosed or not) and therefore would choose to have various courses of treatment to escape the mental anguish of uncertainty, and who can blame them? 

PSA screening has certainly lead to increased prostate cancer awareness since its introduction as a screening tool, but due to the unspecific nature of the PSA test, increased problems with over diagnosis. Advancements are being made with investigating different biomarkers and variations of PSA testing for early detection of prostate cancer. However, in spite of its failings, the PSA test still remains the best screening tool currently available. An advanced approach may be to implement individualised interval screening based on results after first round of PSA screening.  Those men with lower PSA may benefit from lengthened screening intervals, while men with higher levels should be screened more often. 

References

Barqawi AB, Krughoff KJ and Eid K. Current Challenges in Prostate Cancer Management and the Rationale behind Targeted Focal Therapy. Advances in Urology. 2012;May 10. 

Brett T. Prostate specific antigen. Australian Family Physician. Vol. 40, NO. 7, July 2011.

Stamey TA, Caldwell M, McNeal JE, Nolley R, Hemenz M, and Downs J. The prostate specific antigen era in the United States is over for prostate cancer: what happened in the last 20 years. Journal of Urology. Vol 172, no 41, 1297-1301, 2004. 

Rove KO and Crawford ED. Randomized controlled screening trials for prostate cancer using prostate-specific antigen: a tale of contrasts. World J Urol (2012) 30:137-142. 

Colloca G. Prostate-specific antigen kinetics as a surrogate endpoint in clinical trials of metastatic castration-resistant cancer: A review. Cancer Treatment Reviews. 2012 April 12.

Klotz L. Active Surveillance for Favourable-risk Prostate Cancer: Background, Patient Selection, Triggers for Intervention, and Outcomes. Curr Urol Rep (2012) 13:153-159.